Sky & Telescope July 2010

Lessons from Twins of the Sun p. 22 THE ESSENTIAL MAGAZINE OF ASTRONOMY Pluto Crosses “Hole in the Sky” p. 60 JULY 201...

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Lessons from Twins of the Sun p. 22 THE ESSENTIAL MAGAZINE OF ASTRONOMY

Pluto Crosses “Hole in the Sky” p. 60

JULY 2010

Hidden in

Plain Sight How an amateur astronomer discovered the Soap Bubble Nebula p.34

Use the Whole Sky: Shooting Near the Horizon p. 72 Walt Whitman’s “Strange Huge Meteor Procession” p. 28 S&T Test Report Update of a Classic p. 54 Visit SkyandTelescope.com

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July 2010 T. RECTOR / H. SCHWEIKER / NOAO / AURA / NSF

VOL. 120, NO. 1

On the cover: A Kitt Peak professional scope imaged the Soap Bubble here, but it was discovered by an amateur astronomer. FE ATURE S

THI S M O N TH ’ S S K Y

40

Solar Twins

6

By Fred Schaaf

43

July’s Sky at a Glance

45

Binocular Highlight

48

8 10

28 Walt Whitman’s

“Year of Meteors” A team of astro-sleuths from Texas State University once again sets the record straight — this time for one of America’s most famous poets. By Donald W. Olson, Marilynn S. Olson, Russell L. Doescher, & Ava G. Pope

51

Letters 50 & 25 Years Ago By Leif J. Robinson

Planetary Almanac

14

News Notes

Sun, Moon, and Planets

20

Cosmic Relief

By Fred Schaaf

The Sun’s closest stellar analogs hold clues to our own star’s past and future. By Jeff rey Hall

Spectrum By Robert Naeye

By Gary Seronik

46

22 Lessons from

Northern Hemisphere’s Sky

AL S O IN THI S I S S U E

Exploring the Moon

By David Grinspoon

58

New Product Showcase

70

Telescope Workshop

By Charles A. Wood

60

Celestial Calendar

By Gary Seronik

By Alan MacRobert

63

76

Gallery

86

Focal Point

Going Deep By Ken Hewitt-White

By Andrew Vanden Heuvel

67

Deep-Sky Wonders By Sue French

S &T TE S T R E P O R T

COVER STORY

An amateur astronomer unearths a new planetary nebula, hinting that more hidden jewels are lurking th out there. ou By Mike Simmons & Dave Jurasevich

XX X X

72 Shooting Low Low-altitude imaging can double your target list. By Ruben Kier

and

54 A New Astroscanner One of astronomy’s most enduring and distinctive-looking telescopes gets an upgrade. By Gary Seronik

56 Quick Look: Kendrick’s Stargate Observer Tent If you’re an amateur astronomer, camping usually means bringing a telescope along to enjoy the sky. So why not have a tent that accommodates people and telescopes? By Dennis di Cicco

SKY & TELESCOPE (ISSN 0037-6604) is published monthly by Sky & Telescope Media, LLC, 90 Sherman St., Cambridge, MA 02140-3264, USA. Phone: 800-253-0245 (customer service/subscriptions), 888-253-0230 (product orders), 617-864-7360 (all other calls). Fax: 617-864-6117. Website: SkyandTelescope.com. © 2010 Sky & Telescope Media, LLC. All rights reserved. Periodicals postage paid at Boston, Massachusetts, and at additional mailing offices. Canada Post Publications Mail sales agreement #40029823. Canadian return address: 2744 Edna St., Windsor, ON, Canada N8Y 1V2. Canadian GST Reg. #R128921855. POSTMASTER: Send address changes to Sky & Telescope, PO Box 171, Winterset, IA 50273. Printed in the USA.

4 July 2010 sky & telescope


28

FROM THE COLLECTION OF DON OLSON

34 Deep-Sky Discovery

” I HONESTLY CANNOT UNDERSTAND WHY ANYONE WOULD CONSIDER BUYING ANYTHING ELSE.” Jack Newton

Astrophotographer (National Geographic, Life, Newsweek, Photo Life, Sky & Telescope, Astronomy), author, and discoverer of 17 Supernovas.

The LX90™-ACF™ Advanced Coma-Free™ Telescope No other telescope delivers coma-free optics anywhere near the LX90-ACF’s prices. Meade’s LX90 aplanatic Advanced Coma-Free optical system delivers the razor-sharp quality of Ritchey-Chrétien (RC) telescopes selling for thousands of dollars more for the OTA only. So you get Ritchey-Chrétien performance at a fraction of the cost. And the LX90-ACF comes complete with a computerized GoTo mount and all the accessories others manufacturers charge more for. The all-inclusive visual and astro-imaging ready system comes complete with: Strong, rigid duel-fork mount with precision worm-gear drives in both axes that support and drive the OTA with precision Full-size, ultra-stable LX200™ tripod – easy to setup and take down EasyAlign™ to get your telescope up and running with little effort Autostar™ computer control system with pin-point GoTo pointing to over 30,000 celestial objects Smart Drive™ periodic error correction for easier astro-imaging Star diagonal, 26mm Super Plössl eyepiece and 8x50 viewfinder But don’t just take our word for it, listen to Jack Newton: “This high level of optical performance does not exist in any other telescope at or near this price range.” For more information on the LX90 or the complete line of Meade telescopes, go to www.meade.com. Telescopes.com 800.303.5873

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©2010 Meade Instruments Corp. All rights reserved. Specifications subject to change without notice. 30-10023.


Robert Naeye Spectrum Founded in 1941 by Charles A. Federer, Jr. and Helen Spence Federer

The Essential Magazine of Astronomy

Amateur Discoveries

BRUCE BERGER

I’m sure many of you are like me. You love astronomy, but it’s not your only hobby. Perhaps I’m jaded, and I’m not knocking other hobbies, but I think there is something special about amateur astronomy, something that elevates it to the level of greatness. That “something special” is amateur astronomy’s capacity for genuine discovery. Some of these discoveries advance humanity’s collective sum knowledge about our wondrous universe. Astronomy is one of the very few scientific fields where nonprofessionals continue to make significant contributions to research. This issue has articles that exemplify different aspects of astronomical discoveries. The cover story starting on page 34 describes Dave Jurasevich’s discovery of a planetary nebula. This nebula has been sitting there in plain sight for a very long time, but nobody called attention to it until Dave spotted it in one of his CCD images. On page 39, my S&T colleagues Dennis di Cicco and Sean Walker describe their own possible discovery of a nebula. As you can imagine, it’s been generating a lot of buzz around our office! Recent issues have highlighted other amateur discoveries, such as the story in our May 2010 issue about Nova U Scorpii’s January outburst. In the December 2009 issue I wrote an article about two important amateur exoplanet findings. There’s a lot of other exciting stuff going on. For example, during the November 2009 meeting of the Amateur Telescope Makers of Boston, MIT astronomer Michael Person and several club members described their travels to Mexico, Australia, and Nebraska to observe an asteroid occultation of a star in order to pin Bruce Berger prepares for his Brazil trip, where down the asteroid’s size and he’ll monitor a Kuiper Belt object occulting a star. shape. I was fascinated by the scientific objectives and the travel adventures. After the talks, club member Bruce Berger showed me his electronics for an upcoming occultation expedition to Brazil. I was amazed that he could cram so much gear into such a small carrying case. I almost felt like I was talking to James Bond! But as Andrew Vanden Heuvel explains in his Focal Point article on page 86, there’s another kind of amateur discovery that’s equally rewarding: the thrill people experience when they find objects with their backyard telescopes for the first time, even if those objects are well known to science.

EDITORIAL

Editor in Chief Robert Naeye Senior Editors Dennis di Cicco, Alan M. MacRobert Associate Editor Tony Flanders Imaging Editor Sean Walker Editorial Assistant Katherine L. Curtis Editors Emeritus Richard T. Fienberg, Leif J. Robinson Senior Contributing Editors J. Kelly Beatty, Roger W. Sinnott Contributing Editors Greg Bryant, Paul Deans, Thomas A. Dobbins, David W. Dunham, Alan Dyer, Sue French, Paul J. Heafner, Ken HewittWhite, Johnny Horne, E. C. Krupp, Emily Lakdawalla, Jonathan McDowell, Fred Schaaf, Govert Schilling, Ivan Semeniuk, Gary Seronik, William Sheehan, Mike Simmons, Charles A. Wood, Robert Zimmerman Contributing Photographers P. K. Chen, Akira Fujii, Robert Gendler, Babak Tafreshi ART & DESIGN

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Editor in Chief




Letters

Have you ever heard of a major metropolitan county creating a purpose-built astronomy park? St. Charles County (just north of St. Louis, Missouri) has done just this and is working closely with our club. The county has built a very nice facility with a dozen or so concrete telescope pads complete with power outlets. There’s ample parking most nights, though I’ve seen crowds so large that people park on the road. We have restrooms without pesky lights, a picnic table, and a water fountain (see the photo at right). There’s a roll-off observatory with a nice pier, in which the club installed a 10-inch Schmidt-Cassegrain. On one of the pads we have a 16-inch Jones-Bird scope, and a 32-inch is now going in. This is quite a remarkable thing. The astronomy area of the park never closes, and someone is out there on most clear nights. Club members “staff ” the astronomy park every clear Friday, and it’s all free and open to the public. Once a month we have an official outreach event, and I’ve seen as many as 100 people walking around looking through scopes and chatting with club members. And it’s a great way to socialize with fellow astro geeks. On one occasion, the parks department played Jack Horkheimer skywatching videos for the crowd while we hosted our scopes on the pads. A college teacher regularly brings astronomy students to work on assignments. Will Day Weldon Spring, Missouri

On the Web O

JAMES ROE

Government, Good and Bad

North of St. Louis, local government has helped Missouri’s Broemmelsiek Park flourish for amateur astronomers and the interested public.

I have a story in response to your article on light pollution (“Saving the Night Sky,” May issue, page 28). About 10 years ago I stayed at a walk-in campground in Lassen Volcanic National Park in northern California. As darkness fell, a dazzlingly bright all-night light on the side of the restroom turned on. It blinded people as they walked toward the restroom and created an unpleasantly bright environment even inside a tent. I wrote to the park superintendent requesting that the light be shielded to create a more pleasant camping experience and to allow campers to see the stars. The superintendent responded that the light would not be changed and that park visitors enjoy the security provided by bright lights. When one encounters this attitude even at a national park, a place created to preserve the natural environment, it is

Fight Light Pollution:

Getting Started in Astronomy:

Take a Quick Audio Sky-Tour with Our Podcasts:

SkyandTelescope.com/getting started

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SkyandTelescope.com/newsletters

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Do-It-Yourself: SkyandTelescope.com/diy

and 8 July 2010 sky & telescope


difficult to be optimistic about the future of the night sky. Robert Sills Castro Valley, California

Club Observatory Threatened Since 1967 our club, Amateur Astronomers Inc. (AAI), has operated Sperry Observatory at Union County College (UCC) in New Jersey. Last December we received a letter from UCC that it was ending our agreement and we would have to vacate Sperry Observatory by July 21st. The UCC leadership has given a number of different explanations, none of which make sense. Initially it claimed that the observatory was too expensive to keep open. However, the club pays most expenses for operating the observatory and its two large telescopes — a 24-inch Cassegrain reflector, purchased with AAI funds in 1974, and a member-constructed 10-inch refractor, built in 1972. About the only expenses to UCC are the utilities, which would have to be paid regardless of whether the building houses telescopes. Another reason we were given was a need for classroom space, hence UCC’s plan to gut the structure. But the central room is already used as classroom space, and gutting the structure would offer a minimal increase (we had an architect check this out). And, UCC has at least eight classrooms that are hardly used. We


Letters

The club that runs William Miller Sperry Observatory in New Jersey could find it and its two large telescopes evicted.

ST

have no idea of the college’s actual motive. Since closing Sperry would be disastrous to the W AR TM programs we offer the surE YE RS rounding communities, there’s growing public opposition to UCC’s plan. As a result, UCC proposed letting us stay for two years before eviction but told us that some of our members would have to pay $150 for FBI background checks. We are continuing our efforts to drum up public and government support and hope that Sky & Telescope readers will join in. Failure to save Sperry would discourage astronomy clubs from building observatories in cooperation with any schools or colleges, since there would be no assurance that the club and its telescopes wouldn’t be ejected and its work destroyed on some new administator’s whim. With your help, along with that of our E

50 & 25 Years Ago July 1960 Bouncing Radio Waves “Ask the average person about exploration of the solar system, and he will probably give you an image of giant rockets firing complicated instruments into space. Or perhaps he will remind you of the richly detailed picture built up over the centuries from optical studies and added to during the last few years by infrared and radio observations. It may not occur to him, however, that radar techniques are beginning to play an important role, too.” The Moon was the first celestial object detected by radar, in 1946. The surface of Venus was first mapped in the 1960s, and subsequently radar has examined the Sun, other planets, satellites, comets, and asteroids. A Giant Leap “With increasing interest in the moon, the publication of a magnificent atlas of the lunar surface, by G. P. Kuiper with the aid of D. W. G. Arthur, E. Moore, J. W. Tapscott, and E. A. Whitaker, is an event of much importance. Monumental is the word for its form as well as its significance,


local supporters, AAI will continue to advocate the cause of amateur astronomy for many years to come. Please write to me if you want more information. Stewart Meyers East Brunswick, New Jersey [email protected]

Write to Letters to the Editor, Sky & Telescope, 90 Sherman St., Cambridge, MA 02140-3264, or send e-mail to [email protected]. Please limit your comments to 250 words. Published letters may be edited for clarity and brevity.Due to the volume of mail, not all letters can receive personal responses.

Leif J. Robinson for the atlas is a big carton containing nearly 20 pounds of large-scale photographs, taken with some of the world’s greatest telescopes. . . . “The very extensive labor of selecting and preparing the photographs for publication took Dr. Kuiper and his collaborators over four years. Their Photographic Lunar Atlas contains a total of 281 pictures. Of these 212 form the main body of the atlas, each of 44 different regions being shown. . . .” July 1985 Spin-casting Mirrors “In preparation for the needs of the coming decades, [Roger] Angel’s group is enthusiastically working toward the next major milestone: the construction of a larger facility underneath the towering east stands of the [University of Arizona’s] football stadium. Within the new shop will be a massive oven to spin-cast mirror blanks up to 8 meters in diameter. . . .” To date, the Steward Observatory Mirror Lab has cast four 8.4-meter blanks: two for the Large Binocular Telescope in Arizona, the first of seven for the Giant Magellan Telescope in Chile, and one for the Large Synoptic Survey Telescope, also in Chile.

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News Notes

To get astronomy news as it breaks, visit SkyandTelescope.com/newsblog. S ky

One Supernova, Many Camera Angles Sept 3, 2008

Sept 14, 2009

Light echo

CFA / KPNO

How often have you wished you could see some nebula or galaxy from a different angle? Alas, you’d need a starship that could flit across the light-years. But ingenious astronomers have found a way to get new camera angles from here on Earth: by watching light echoes. Cassiopeia A, imaged below by its X-ray emission (by the Chandra X-ray Observatory), is the expanding debris of a supernova that exploded around the year 1680 as seen from Earth. It’s located about 11,000 light-years away. The supernova blast itself was bright enough to illuminate dust clouds several hundred light-years from it, and we see some of those clouds lighting up right now, 330 years late. This happens wherever the total travel path of the light, from supernova to cloud to us, is 330 light-

years longer than from the supernova directly to us. The pictures above show one such cloud lighting up. An international team of 24 astronomers took spectra of the reflected supernova light using one of the 10-meter Keck telescopes in Hawaii. The spectra show a replay of

what happened in the explosion. Reflections from different clouds show replays as seen from different angles. And these show something interesting. The supernova blast was asymmetrical. In one direction, as revealed by blueshifted spectral lines, stuff expanded outward from the blast some 4,000 kilometers per second faster than in other directions. This high velocity occurred in more or less the same direction as a jet that’s visible in a 3-D model of the debris remnant itself that was pieced together last year (S&T: April 2009, page 18). That model indicates that the star’s outer layers blew off spherically, while the star’s core blasted out in a flattened plane, including an especially highvelocity jet that may have been directed along the progenitor star’s rotation axis. And indeed, the neutron-star cinder of the star’s core is, today, flying at least 350 km per second opposite from the direction of the jet and the high-velocity light echoes. Apparently it was kicked that way by the asymmetric blast.

NASA / CXC / SAO / D.PATNAUDE ET AL.

Left: In this X-ray image of the supernova remnant Cassiopeia A, low-energy X-rays are shown as red, intermediate energies as green, and high energies as blue. Above: Deep images taken a year apart show an interstellar cloudlet lighting up as illumination from the Cas A supernova washes over it. Amateur deep-sky imagers can join the hunt for such supernova light echoes; see the June 2008 Sky & Telescope, page 28.



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News Notes

The supermassive black hole in the galaxy M87 emits an especially photogenic jet.

Rho Oph

The Spins of Black Holes

Epsilon Aurigae’s Eclipser Now that the partial eclipse of the nakedeye star Epsilon Aurigae is well under way (April issue, page 12), the current genera-

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A group led by Ruth A. Daly (Penn State University) has developed a way to judge the spin of a black hole based on its mass and the power of any jets that it’s emitting. The group applied the method to 55 supermassive holes at the centers of galaxies and found them to be spinning at from 10% to 100% of the maximum possible spin rate, which is limited by the speed of light. The most distant holes, seen 10 billion years in the past when the universe was young, turn out to spin at the maximum possible speed. Those relatively nearby, in essentially today’s universe, range from 80% of the maximum spin (for the most powerful jet emitters) down to 10% for some of the weaker ones. This nicely matches predictions based on the fact that, throughout the vagaries of cosmic history, accretion of counterrotating material should spin a black hole down more than the accretion of co-rotating material will spin it up.

tion of astronomers is getting its crack at figuring out what’s going on. They’ve already scored a major triumph. A team using the CHARA Array on Mount Wilson in California has constructed interferometric images of the face of the giant, F-type star. They show a dark, oblong disk, seen nearly edge on, beginning to slide across it — almost exactly as expected. The star is 2.0 milliarcseconds wide in the infrared images below, corresponding to a diameter of 1.3 astronomical units. As the disk continues to cross the star in months to come, the CHARA astrono-

Nov. 3, 2009

Dec. 3, 2009

0.25 AU

A dark finger intrudes from the lower left across the face of Epsilon Aurigae, resolved for the first time by interferometry in these images from the CHARA Array.



mers predict that it will prove to be 10 a.u. long, about the diameter of Jupiter’s orbit. Details appear in the April 8th Nature. Many other studies are continuing; the eclipse should last until May 2011.

The Sky in a Cold New Light Europe’s Planck spacecraft is mapping the sky at nine millimeter and submillimeter wavelengths — the obscure part of the spectrum between infrared and radio. Planck’s main goal is to map the cosmic microwave background, but this requires identifying and removing all glow from the Milky Way and other astronomical sources. Above is an image built from this “throwaway” data. Red represents 0.54-mm (540-micron) emission from very cold interstellar dust at a temperature of about 10 kelvins. Green represents 0.35-mm waves, and blue 0.1 mm (obtained by the IRAS satellite), showing warmer dust at a few tens of kelvins. Most of the coldest dust lies in the foreground less than 500 light-years away; summer-sky astrophotographers will recognize the dark nebulae running

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from Rho Ophiuchi to the Pipe and Horse Nebulae in Sagittarius. They’re seen not as their usual dark silhouettes but glowing with their own thermal emission. Warmer dust in the Milky Way’s plane, seen edge on, extends far away into the background. Planck’s first cosmology results are expected early next year.

mon they may be — for good reason. Any small, habitable, terrestrial worlds in such a chaotic mix would be expelled or destroyed by the antics of the crazy giants. Failure to consider such “anthropic” self-selection effects, it’s now obvious, made it a mistake for astronomers ever to assume that our solar system would necessarily be normal.

Wrong-Way Planets Are Common

A Star to Stir Up Comets Will any known star ever pass close to the solar system? That depends on what you mean by “close.” If it’s close enough to stir up extra comets falling in toward the Sun, probably yes. Gliese 710 is an obscure, 10th-magnitude orange dwarf 63 light-years away in Serpens. Astronomers first took note of it about a decade ago, when Joan GarcíaSánchez (Jet Propulsion Laboratory) and others found, based on positional observations by the Hipparcos satellite, that in roughly 1.5 million years it would pass about 1.3 light-years from the Sun. A new analysis by Vadim V. Bobylev (Pulkovo Observatory, Russia), based on the 2007 refinements of the Hipparcos data, now finds that in about 1.4 million years the star has an 86% chance of passing within the outer edge of the Oort Cloud, the Sun’s reservoir of long-period

Before . . .

comets. That’s if the edge is assumed to be 1.6 light-years (100,000 astronomical units) from the Sun. But the disturbance will boost the rate of incoming comets that could hit Earth by only about 10%. Much closer stellar encounters in the distant past have left their marks, such as the sharp cutoff of the Kuiper Belt at 60 a.u. from the Sun and the otherwise inexplicable orbit of the dwarf planet Sedna, which ranges from 76 to 976 a.u. No mere planetary encounter could have sent Sedna that far out and parked it in this orbit.

A Very Fresh Ray Crater The last thing that most people remember about the ill-fated Apollo 13 mission, whose astronauts barely made it back alive, was what became of its third-stage rocket booster. The 14-ton booster hit Oceanus Procellarum near Copernicus on April 14, 1970, traveling 2.5 km per second. That’s faster than a speeding bullet, but slower than most astronomical impactors. Now NASA’s Lunar Reconnaissance Orbiter has found the site with its high-resolution camera. At first glance it looks like an ordinary small ray crater, despite being a mere 40 years old. The crater is about 115 feet (35 meters) across, and some of its rays extend for more than a mile. ✦

After

100 Meters



NASA / GSFC / ARIZONA STATE UNIVERSITY

Star formation isn’t simple. It’s not just about a gas cloud collapsing in on itself by gravity. Among other things, the random motions in any given cloud will likely give it too much angular momentum; the resulting star would spin so fast it would fly apart. One reason stars can form at all is because a complex process sorts most of the mass into the central object, and most of the angular momentum into a big, low-mass disk orbiting it. This disk is where planets form. That’s why our solar system consists of planets revolving the same way the Sun rotates. But exoplanet systems are just full of surprises. Planet hunters recently found giant worlds close to their stars orbiting at a steep angle to the star’s rotation, or even in the opposite direction (S&T: December 2009, page 22). These wrong-way oddballs are turning out to be not the exception, but perhaps the rule. By carefully observing rotational blueshifts and redshifts in the spectra of 27 stars while their planets transited, a Geneva Observatory team found that more than half of these planets are seriously inclined to their star’s rotation. Six have inclinations greater than 90°; they revolve closer to backward than forward. How can this be? We’re probably seeing yet another relic of early planetary chaos. Apparently a star often forms with so many giant planets that they interact strongly and throw one another every which way. Some are probably flung clear off, and the remaining few are left in wild orbits. We, of course, don’t find ourselves in such a system, regardless of how com-

NASA

ESO / L. CALÇADA

News Notes


Cosmic Relief David Grinspoon

Venus Lives! Venus Express has found compelling evidence for active volcanoes.

“Is venus geologically active today?”

VOLCANIC HOT SPOT This image of Venus’s surface has been color-coded to reveal variations in infrared emission from surface rocks as measured by the Visible and Infrared Thermal Imaging Spectrometer aboard Venus Express.

NASA / JPL / CALTECH / ESA

remains one of the many important questions in planetary science. A recently published result seems to move the answer from “We think so” toward “Yes, we’ve found the evidence!” Venus is the only other Earth-sized planet we know. That should change soon, but we won’t be able to closely study the new extrasolar Earths, separated from us by the vast interstellar divide. So Venus presents our only opportunity to learn the detailed, long-term workings of another Earth-sized world.

Venus’s surface is beckoning us with its compelling answers so close and yet so hard to see. It’s the most relevant planetary surface to the major questions about what makes our own home planet tick. But it’s also freakishly difficult to explore, due to both the crushing, searing surface conditions that destroy probes and keep NASA wary of mission proposals, and the thick, unbroken global cloud deck that frustrates direct orbital or telescopic inspection. Yet, just as the interstellar depths have finally been breached with the relentless cleverness of planet-hunters, Venus’s surface is gradually surrendering her mysteries. Galileo’s 1990 Venus flyby revealed that the atmosphere is transparent in certain near-infrared wavelengths that allow a spacecraft to see the surface. In 2005 the European Space Agency launched Venus Express, the first orbiter with the right instruments to exploit these spectral windows. These

infrared maps have revealed that certain features, which resemble Hawaiian-type hot-spot volcanoes, are covered with a different type of rock than the surrounding plains. A team analyzing these maps recently announced in Science that these areas are consistent with fresh volcanic minerals that have not yet chemically reacted with the hot, caustic atmosphere. These areas must have experienced recent eruptions, strongly implying the volcanoes are active today. Many scientists, myself included, have written that Venus today is probably volcanically active based on many pieces of circumstantial evidence, including likely volcanic gases in the atmosphere and the fresh appearance of the youngest volcanoes in radar images. Yet, before this new result, we lacked a “smoking gun” to move this question into the “definitely yes” column. Now we can study the structures and active functioning of a nearby almost-Earth. Venus should be active, since size is the most important factor in controlling a planet’s internal cooling. For example, Mars is smaller, cooler inside, and mostly dead geologically. Yet, given their nearly identical sizes, Venus and Earth should be more similar. Venus lacks plate tectonics, the system of interior motions and surface movements that organizes most geological activity on Earth and removes heat from our planet’s interior. Instead, Venus may be losing heat today mostly through these hot-spot volcanoes. But smooth volcanic lavas, which are not made by hot spots, dominate most of Venus. So apparently Venus has changed her volcanic style radically over the eons. We don’t know why Venus changed, but it may have to do with the runaway greenhouse that occurred billions of years ago, evaporating her oceans and leaving her hot and dry. Water seems to be the key to Earth’s uniqueness, from life to climate to geology. Perhaps the drying out of Venus changed the properties of her interior rocks, leading to the cessation of plate tectonics, and causing changes in volcanic style. We need future missions to understand this history, but now we know there’s an active planet next door from which we can learn about the possible lives and fates of Earth-like planets. ✦ David Grinspoon is Curator of Astrobiology at the Denver Museum of Nature & Science and author of the 1998 book Venus Revealed. His website is www.funkyscience.net.



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Sun–Earth Connection

Lessons Solar Twins j ef f r e y h a l l

T he Sun’s closest stellar analogs hold clues to our own star’s past and f uture. PHOTOGRAPH BY GREG PIEPOL

One of the pleasures

of doing astronomy in northern Arizona is living in a land of wide horizons, brilliant sunshine, and spectacular topography. For two millennia, from about 1200 BC, this area was inhabited by the Anasazi. But around 1300 AD the Anasazi abandoned their longtime home. Archaeologists have posited a number of causes, but a contributing factor appears to have been a severe drought between about 1270 and 1300. This interval coincided roughly with a period of low solar activity called the Wolf Minimum, an event similar to the more famous Maunder Minimum of 1645–1715. The Maunder years corresponded

to a lengthy run of severe winters in Europe, Asia, and North America. Correlation of regional climate change with solar activity does not demonstrate causation. But it raises curiosity and motivates us to understand solar variability. Observations of solar brightness from space span only 30 years and quantitative sunspot data dates back only 400 years — a painfully short window on a star’s life. Moreover, the Sun provides only one example of stellar behavior. Explaining the Sun by itself is akin to explaining humanity by observing one person for one second. Fortunately, each night a lovely laboratory wheels by overhead that we can use to develop a more informed perspective.



STELLAR PIONEER In the 1960s, Mount Wilson Observatory astronomer Olin Wilson was the first to detect activity cycles on other stars, pioneering research that continues to the present day.

Stellar Cycles

ACTIVE SUN Opposite page: When imaged in H-alpha light, the Sun reveals light and dark features that originate from magnetic activity. The Sun’s activity rises and falls in cycles that average about 11 years. Ongoing observations since 1966 have shown that many stars similar to the Sun also have activity cycles of similar length and magnitude.

S&T PHOTO ARCHIVE

of roughly 1300–1700. In 1978 satellite observations of the Sun’s total brightness (irradiance) began, revealing that it’s not constant: at activity maximum, the Sun is 0.1% brighter than at minimum. Evidence also accumulated that solar irradiance varies on longer timescales, including a steady increase since the end of the Maunder Minimum (S&T: March 2009, page 30). These observations fueled interest in the degree to which the Sun affects Earth’s climate, but also highlighted the need to know if it was a typical G2 star, and how it might have varied before precise measurements were available.

Solar Twins One approach is to study the variations of stars similar to the Sun. If we can observe a statistically significant number of them, we should be able to constrain the range of behavior they — and by inference, the Sun — can exhibit. But most of Wilson’s stars were rather different from the Sun in age, mass, and activity level. This was sensible enough, since he was seeking to detect stellar cycles across a broad swath of the H-R diagram. But to use stars as solar proxies, we need a more narrowly defined sample, and since about 1980, astronomers have been searching for “solar analogs” and “solar twins.” These terms are qualitative but restrictive: a solar twin should differ from the Sun in its essential characteristics by no more than a few percent.

K line (393.37 nanometers)

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JEFFREY HALL, ET AL.

We owe much of this informed perspective to Olin Wilson (1909–1994), who in 1966 began observing the activity of 91 cool stars at the Mount Wilson Observatory near Los Angeles. (“Cool” does not imply skillful moves at a celestial discotheque, but, roughly, spectral types F to M.) It was not then known if cool stars had Sun-like activity cycles. To find the answer, Wilson observed the Fraunhofer H and K absorption lines of singly ionized calcium, which are sensitive to changes in activity. We cannot image active features such as dark spots and bright faculae in distant stars as we can for the Sun, but we can observe them indirectly using spectral features such as these calcium lines. Wilson watched his stars for 12 years and in 1978 published a beautiful paper demonstrating that many other stars indeed have activity cycles and — significantly — that some do not. The study warranted further work, and following Wilson’s retirement, the program continued another 25 years under the direction of Sallie Baliunas (Harvard-Smithsonian Center for Astrophysics). By 2003 Baliunas, Wilson, and their colleagues had amassed a 37-year record of activity in cool stars. Since 1994, thanks to support from the National Science Foundation, my colleagues and I have been making spectroscopic observations of many Mount Wilson stars and others at Lowell Observatory in Flagstaff, Arizona. Greg Henry of Tennessee State University is conducting complementary brightness observations of these stars using robotic photometric telescopes at the Fairborn Observatory in southern Arizona. About 60% of Wilson’s stars have activity cycles like the Sun’s. A quarter vary irregularly, but they tend to be younger and more rapidly rotating than the Sun, properties that enhance activity. The remaining 15% show little or no variability. Are these interesting cases of stellar analogs of the Maunder Minimum? Records from sources such as ice cores suggest the Sun may spend about 15% of its life in such “grand minimum” states, so these observations may give us a glimpse of the Sun’s past. The Maunder Minimum got its name in 1976, when astronomer Jack Eddy (1931–2009) called attention to the near absence of sunspots in the mid- to late 17th century and to the corresponding unpleasant weather in Europe, one of the severest episodes of the Little Ice Age

SOLAR SPECTRUM Numerous dark lines appear in this small section of a solar spectrum, indicating wavelengths of light absorbed by atoms and molecules in the Sun’s atmosphere. The H and K Fraunhofer lines arise from ionized calcium. The amount of emission in the cores of these lines rises and falls with increases and decreases in the Sun’s magnetic activity. By studying these spectral lines in other stars, astronomers can gauge their activity levels.

Sk yandTelescope.com July 2010 23


AKIRA FUJII


Antares

NEAR-SOLAR TWIN The 5.5-magnitude G2 star 18 Scorpii (arrowed) is a near twin of the Sun, located 46 light-years away in northern Scorpius. The variations of 18 Sco, and stars similar to it, can help astronomers infer the long-term variability of the Sun.

DATA: JEFFREY HALL, ET AL.

Activity level

Psi Serpentis Spectral Variations

Jan1 1998

Jan1 2000

Jan1 2002

Jan1 2004

Jan1 2006

Jan1 2008

Jan1 2010

STAR IN TRANSITION The author’s research team has plotted more than a decade of H and K spectral-line variations of the 5.9magnitude G5 star Psi Serpentis, which is not a solar twin but a reasonably Sun-like star. The blue diamonds show the mean level of magnetic activity in the star during each observing season. This star may have made a transition from a low-activity state in 1997–2001 to a vigorous, roughly 4-year cycle since then. Stars like Psi Serpentis may provide clues about solar behavior that occurred long before the era of modern instrumentation.

So all we need to do is find and observe lots of solar twins. Even better would be if they displayed both activity cycles and Maunder Minimum-like states; we could then use those non-cycling stars to look through the glass darkly into the Sun’s past. Easy, right? Wrong. Until 2006 the number of accepted solar twins was — drum roll please — one. It’s an unassuming 5th-magnitude star in Scorpius with the designation HD 146233. More easily remembered as 18 Scorpii, it was advanced as a solar twin in 1997 by Gustavo de Mello (Universidade Federal do Rio de Janeiro, Brazil) and Licio da Silva (Observatório Nacional, Brazil). It was not one of Wilson’s original stars, but we have been observing its activity and brightness for more than a decade. Its cycle appears a few years shorter than the Sun’s, but its activity level and amplitude are similar. Finding solar twins other than 18 Sco has been difficult. In order to observe a significant sample of stars repeatedly, we forgo faint ones because it takes too long to obtain quality observations. This limits the sample and we have had to make do mostly with stars that are good but not ideal solar proxies. Fortunately, surveys are now going fainter. In 2007 Jorge Meléndez (Centro de Astrofísica da Universidade do Porto, Portugal) and Ivan Ramírez (Max-Planck-Institut für Astrophysik, Germany) identified two magnitude-8 solar twin candidates with even better chemical abundance matches to the Sun than 18 Sco. As such stars turn up, we can drop some of the less Sun-like stars in our sample. Through careful study of high-resolution spectra, which allows determination of essential parameters including rotation rate, temperature, and chemical abundances, we’re gradually finding more genuine proxies for the Sun. So far, they’re all within a few hundred light-years. No doubt many more await discovery. In 2006 Mark Giampapa (National Solar Observatory), Richard Radick (NSO), Sallie Baliunas, and I published an analysis of faint (magnitude 12 to 14) solar twins in the open cluster M67. Now, with new surveys such as those being made by NASA’s Kepler spacecraft, and upcoming facilities such as Lowell’s 4.3meter Discovery Channel Telescope, there is a growing potential to study a much larger sample of solar twins.

The Solar–Stellar Connection Until this year, a vexing property of Olin Wilson’s original 91 stars was their variability. As their cycles waxed and waned, they brightened and dimmed two to five times more than the Sun does during its cycle. Is the Sun therefore special? Are its brightness variations unusually small? And are life-favoring conditions on Earth partly due to special characteristics of the Sun? As always, the answers are complex. In a recent paper, we show that the amplitude of the brightness variations of 18 Sco, and a number of other good solar analogs, are com-



GREG HENRY

FAIRBORN OBSERVATORY

SOLAR TWIN SEARCHER At the Fairborn Observatory in southern Arizona, a set of robotic photometric telescopes observes the brightness variations of Sun-like stars so astronomers can compare them to spectroscopic variations. One of these scopes is pictured here. Inset: Greg Henry conducts this part of the study.

But there’s an additional angle to the story. The solar analogs match the Sun well in their overall behavior, but the detailed correlation of activity and brightness is generally not as good as for the Sun, which so far has been observed to brighten and fade in lockstep with its rising and falling activity. For example, the star Psi Serpentis (HD 140538) may have made a transition from a non-cycling state to a vigorous, four-year cycle starting

parable to those of the Sun, rising and falling by around 0.1%, and that they have comparable magnetic activity levels. The larger stellar variability in the original sample appears to have been a selection effect: many of those stars were more active and younger than the Sun, and therefore not ideal representatives of solar behavior. Solar-like variations thus seem to be typical of Sun-like stars, but only if we define the Sun-like star club rather exclusively. WHAT IS A SOL AR T WIN? IIn a 1996 paper, Giusa Cayrel de Strobel (Observatoire de Paris-Meudon, France) wrote that a solar twin should possess “fundamental physical parameters (mass, chemical composition, age, effective temperature, luminosity, gravity, velocity fields, magnetic fields, equatorial rotation, etc.) very similar, if not identical to those of the Sun.” Even if 18 Scorpii falls very slightly short of this restrictive definition, no stars brighter than about magnitude 8 completely satisfy it. Solar twins — both cycling and in stellar Maunder Minima — are likely waiting for us, but they will be faint and will require time and patience to characterize.

Relatively Close Near-Solar Twins Right ascension

Star

Sun

— h

Visual mag.

Mass

Effective temp (K)

Iron/hydrogen ratio (log units)

Distance (l-y) Planets

—

–26.7

1.00

5780

0.00

0

Yes

s

47 Urs. Maj. 10 59 28

+40º 25.8′

5.1

1.29±0.06

5860

0.06

46

Yes

18 Scorpii

16h 15m 37s

–08º 22.2′

5.5

1.04±0.03

5837±36

0.04±0.024

46

?

16 Cygni B

19h 41m 52s

HD 133600 HD 101364

m

Declination

+50º 31.0′

6.2

1.10±0.06

5753

0.00

70

Yes

h

m

s

+06º 17.6′

8.2

1.00±0.03

5810±36

0.02±0.024

170

?

h

m

s

+69º 00.5′

8.7

1.00±0.03

5785±36

0.01±0.024

217

?

15 05 13

11 40 28



Watts/square meter

1362

Watts/square meter/nanometer


1.176

Solar Brightness Variations

1361

RUSTY TWEED (LOWELL OBSERVATORY)

Total solar irradiance

1360 1359

Spectral irradiance (389.75 nm)

1.174

DATA: JERALD HARDER, ET AL. / SORCE

1.172 1.170 1.168 1.529 1.528 Spectral irradiance (656.16 nm)

1.527 1.526 2004

2005

2006

2007

2008

2009

SOLAR IRRADIANCE The top graph shows that the Sun’s total energy output (irradiance) declined slightly as the solar cycle approached minimum and is now beginning to rise with the onset of cycle 24. The middle graph shows the Sun’s output around 390 nanometers, in the near-ultraviolet. The bottom graph shows the Sun’s output around 656 nanometers, in the red part of the visible spectrum. The Sun’s energy output in the two wavelength regimes differs considerably. In the ultraviolet, it varies directly with activity, just like the total irradiance. But in the red, it varies inversely with activity — a surprising result.

in 2001. But we did not see any significant increase in its brightness when it left its low-activity state, and there is a hint in the data that it may have flipped from a direct (that is, like the Sun) to an inverse (the opposite of the Sun) activity–brightness relationship as it has begun cycling again.

The Sun and Climate The stars show that what we think of as normal solar behavior — an 11-year cycle and a brighter Sun at activity maximum — is just one of a number of activity–brightness scenarios. If the present unusually long and deep solar minimum arises from the Sun’s making a transition to a different state, it would be revealing and exciting. This is certainly possible. Even if another Maunder Minimum is not imminent, several recent papers have argued that the “Modern Maximum” of solar activity is ending, with an upcoming period of weaker cycles likely. The current minimum has been long, but active regions and spot groups associated with cycle 24 are appearing (S&T: August 2009, page 26) and we will know in a few

Download a FREE BONUS PODCAST To listen to a podcast interview with author Jeffrey Hall, visit SkyandTelescope.com/ solartwins.

RESEARCH TEAM Above: Astronomers (left to right) Len Bright, Jeffrey Hall, Brian Skiff, and Wes Lockwood search for spectral changes indicative of stellar variability.

years if the now-rising cycle 24 is in fact weak. The behavior of Sun-like stars suggests that significant stellar dimming during grand minima is unlikely, and very recent work by Georg Feulner and Stefan Rahmstorf (Potsdam Institute for Climate Impact Research, Germany) finds that a solar grand minimum would reduce the global mean temperature by 0.1 to 0.3ºC, not enough to offset the effect of increasing greenhouse-gas concentrations. But the impact of the 70-year Maunder Minimum, especially in Europe, Siberia, and North America, is well established, and even the effects of the 11-year cycle can be detected in today’s climate. A change in solar behavior could induce further significant regional changes in temperature and precipitation. Progress in quantifying these effects is likely to come from studying not just the total variations of the Sun and stars, but the spectral distribution of those variations. Since 2003 the Solar Radiation and Climate Experiment (SORCE) satellite has observed changes not only in the Sun’s total brightness, but also over particular wavelengths in the ultraviolet, optical, and infrared. These data have yielded a very big surprise. In some spectral regions, the Sun brightens as its activity rises, but in others, including part of the optical and the infrared, it dims. If we see this behavior continue as solar cycle 24 rises, it will have major implications for our interpretation of stellar variations. Are the spectral variations of Sun-like stars similarly distributed? What are the implications for Earth’s climate? These questions are still unanswered. Before the Sun makes any of us latter-day Anasazi, we would like to know. ✦ Jeff rey Hall is an astronomer at the Lowell Observatory in Flagstaff, Arizona. He and his colleagues Wes Lockwood (Lowell), Brian Skiff (Lowell), Len Bright (Lowell), and Greg Henry (Tennessee State University) have observed activity and brightness variations of Sun-like stars for the past 15 years.



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Literary Mystery

“Year of

Walt Whitman’s

HARPER’S WEEKLY ILLUSTRATIONS OF THE 1860 METEOR PROCESSION FROM THE DON OLSON COLLECTION

A team of astro-sleuths from Texas State University once again sets the record straight

caption xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx



Meteors” — this time for one of America’s most famous poets. Donald W. Olson, Marilynn S. Olson, Russell L. Doescher, & Ava G. Pope Leaves of Grass, the great collection by American poet and avid skywatcher Walt Whitman (1819–92), includes a poem with the intriguing title “Year of Meteors. (1859– 60.).” The verses make topical references to newsworthy events of the time: the hanging of abolitionist John Brown on December 2, 1859; the arrival of the giant steamship Great Eastern in New York Harbor on June 28, 1860; the visit of the Prince of Wales to New York City during October 1860; and the presidential election won by Abraham Lincoln on November 6, 1860. Of special interest to astronomers, Whitman describes a comet and a meteor: Nor the comet that came unannounced out of the north, flaring in heaven, Nor the strange huge meteor procession, dazzling and clear, shooting over our heads, (A moment, a moment long, it sail’d its balls of unearthly light over our heads, Then departed, dropt in the night, and was gone;) Despite the literary significance of Leaves of Grass, previous scholars have failed to precisely identify the celestial events that served as the inspiration for these two astronomical references. Identifying the “comet that came unannounced out of the north, flaring in heaven” is relatively straightforward. The direction, motion, and brilliance make it clear that Whitman is referring to Comet 1860 III, also known as the Great Comet of 1860. Discovered in the northern constellation Auriga on June 18th, this comet developed a tail about 15° to 20° long and reached a maximum brightness of about 1st or 2nd magnitude. By the second half of July, the comet moved southward through Crater and Corvus and became a Southern Hemisphere object. The mysterious reference to a “strange huge meteor procession” poses a much more difficult identification problem. While previous attempts to

YEAR OF METEORS. (1859–60.) YEAR of meteors! brooding year! I would bind in words retrospective some of your deeds and signs, I would sing your contest for the 19th Presidentiad, I would sing how an old man, tall, with white hair, mounted the scaffold in Virginia, (I was at hand, silent I stood with teeth shut close, I watch’d, I stood very near you old man when cool and indifferent, but trembling with age and your unheal’d wounds you mounted the scaffold;) I would sing in my copious song your census returns of the States, The tables of population and products, I would sing of your ships and their cargoes, The proud black ships of Manhattan arriving, some fill’d with immigrants, some from the isthmus with cargoes of gold, Songs thereof would I sing, to all that hitherward comes would I welcome give, And you would I sing, fair stripling! welcome to you from me, young prince of England! UNLESS OTHERWISE NOTED, ALL ILLUSTRATIONS ARE FROM THE COLLECTION OF DON OLSON



Literary Mystery pinpoint the event cover a range of interesting 19thcentury sky phenomena, none of them reasonably match the poem’s description.

And there is the meteor-shower, wondrous and dazzling, the 12th – 13th Eleventh Month, year 58 of The States, between midnight and morning.

1833 Leonids?

See you! the spectacle of the meteors overhead.

In his 1951 book Walt Whitman — Poet of Science, Joseph Beaver asserts that “Year of Meteors” is based upon the great Leonid meteor storm of November 12–13, 1833. We know that Whitman observed this spectacular event, because the New York Public Library manuscript collection includes his handwritten description:

See you! myriads in all directions, some with long shiny trains,

The shower of meteors — this occurred in the night of 12th – 13th Nov. 1833 — toward morning — myriads in all directions, some with long shining white trains, some falling over each other like falling water — leaping, silent, white, apparitions around up there in the sky over my head.

During the 1833 Leonids, thousands of meteors descended all over the sky for a period of several hours, continuing until dawn and even after sunrise. But the Leaves of Grass poem describes a meteor procession that lasted for a “moment, a moment long . . . Then departed, dropt in the night, and was gone.” The year 1833 is inconsistent with the poem’s title, and the visual appearance is completely wrong.

1858 Leonids?

The “year 58” in this passage has led some Whitman scholars to link this description to the poem in Leaves of Grass. A claim that the poet observed a meteor shower on “November 12–13, 1858” appears as a footnote in the important volume, Introduction to Leaves of Grass: Comprehensive Reader’s Edition (1965), edited by Harold Blodgett and Sculley Bradley. Larzer Ziff ’s essay in Critical Inquiry (1984) reiterates that on “the night of 12 November 1858, Walt Whitman witnessed a meteor shower.” Nevertheless, Whitman’s phrase “year 58 of The States” does not refer to the year 1858. By the conventional method of counting employed in 19th-century almanacs (and used on the title pages of some books by Whitman himself), the 1st year of independence covers July 4, 1776 to July 4, 1777. As such, the 58th year is July 4, 1833 to July 4, 1834, the period in which the great Leonid storm that astonished observers (including Whitman) occurred. The Library of Congress manuscript definitely refers to the 1833 Leonids. Furthermore, memorable Leonid meteor

COURTESY JUDITH FILENBAUM HERNSTADT

Some modern authors have been misled by another text fragment, handwritten by Whitman and preserved in the Library of Congress:

Some rolling over each other like water poured out and falling — leaping, silent, white apparitions of the sky.

Frederic Church’s painting, The Meteor of 1860, provided the key that the authors used to unlock a longtime literary mystery.



JAMES BAKER

One of the most spectacular Earth-grazing fireballs of the 20th century occurred over the American West on August 10, 1972. The fireball is seen here passing over the Teton Range in Wyoming.

storms took place in 1833 and 1866, while 19th-century astronomical journals show that there was no strong Leonid activity recorded in 1858.

1859 Daylight Fireball? Most recently, scholars have connected Whitman’s meteor poem to a spectacular fireball seen on November 15, 1859. This identification appears in a 1980 Whitman biography by Justin Kaplan. In 1989 Kent Ljungquist developed the idea in more detail in an article, and several books repeat it as recently as 2007. But the 1859 event involved only one fireball, and Whitman refers to multiple meteors in a “procession” that “sail’d its balls of unearthly light over our heads.” Moreover, contemporary newspaper stories and scientific journals report that the November 15, 1859, meteor fell from the daytime sky over New York City about 9:30 a.m., while the poem describes fireballs “in the night.” The number of fireballs is wrong, and the time of day is wrong. But if all of these identifications are incorrect, then what was Whitman describing in his poem?

Meteor Showers and Earth Grazers During meteor showers such as the Perseids, Leonids, and Geminids, when the shower radiant is high in the sky, meteors descend through Earth’s atmosphere in a relatively short time, ranging from a fraction of second to perhaps a few seconds. When a shower radiant is near the horizon, however, an observer can see a meteor for a longer time as it follows a path that can extend almost from horizon to horizon. If the speed of one of these Earthgrazing meteors is unusually slow, not much greater than Earth’s escape velocity (about seven miles per second),

(Remember you surging Manhattan’s crowds as you pass’d with your cortege of nobles? There in the crowds stood I, and singled you out with attachment;) Nor forget I to sing of the wonder, the ship as she swam up my bay, Well-shaped and stately the Great Eastern swam up my bay, she was 600 feet long, Her moving swiftly surrounded by myriads of small craft I forget not to sing; Nor the comet that came unannounced out of the north flaring in heaven, Nor the strange huge meteor-procession dazzling and clear shooting over our heads, (A moment, a moment long it sail’d its balls of unearthly light over our heads, Then departed, dropt in the night, and was gone;) Of such, and fitful as they, I sing — with gleams from them would I gleam and patch these chants, Your chants, O year all mottled with evil and good — year of forebodings! Year of comets and meteors transient and strange — lo! even here one equally transient and strange! As I flit through you hastily, soon to fall and be gone, what is this chant, What am I myself but one of your meteors? ○



Literary Mystery

Meteor Processions An even more spectacular phenomenon can occur if a large Earth-grazing meteor fragments early in its encounter with the atmosphere, creating multiple meteors traveling in nearly identical paths. Known as a meteor procession, the slow, stately passage of a series of fireballs is an amazing event. Perhaps the most remarkable one took place over Canada and the United States on February 9, 1913. Canadian astronomer Clarence Chant collected eyewitness accounts, primarily from Ontario, and noted: “To most observers the outstanding feature of the phenomenon was the slow, majestic motion of the bodies; and almost equally remarkable was the perfect formation which they retained.” Dozens of fireballs in three main groups passed over a ground track that extended from Saskatchewan through Ontario and New York to ships in the Atlantic Ocean.

July 20, 1860, Meteor Procession

then the fireball can remain visible to a single observer for about a minute, and it can take about two minutes to pass over a ground track that can extend more than a thousand miles. The most spectacular recent example of such an Earth-grazing meteor is the daylight fireball sighted in the American West on August 10, 1972. The meteor entered the atmosphere above Utah and was moving horizontally at nine miles per second when it was closest to the ground 36 miles (58 km) above Montana (the only place where loud sonic booms were heard). It continued northward, leaving the atmosphere and escaping back into space above Alberta. The event was widely seen from a ground track that extended for 900 miles. It was famously captured in a still photograph by James Baker and a Super 8 movie by Linda Baker. They were at Jackson Lake, Wyoming and watched the daylight fireball passing over the spectacular Teton Range. Observers there were able to follow this Earthgrazing meteor for about 50 seconds as it passed slowly northward across the sky.

ME TEOR PRO CE SSIONS August 18, 1783 Scotland, England, English Channel, France July 20, 1860 Wisconsin, Michigan, Ontario, New York, Pennsylvania, Atlantic Ocean December 21, 1876 Kansas, Missouri, Illinois, Indiana, Ohio, Pennsylvania February 9, 1913 Saskatchewan, Manitoba, Minnesota, Michigan, Ontario, New York, Pennsylvania, New Jersey, Atlantic Ocean



GUSTAV HAHN’S 1913 METEOR PROCESSION PAINTING: UNIV OF TORONTO ARCHIVES

Despite the assertions of previous literary scholars, the great Leonid meteor storm on the night of November 12–13, 1833, though witnessed by Walt Whitman, was not the event mentioned in the poem “Year of Meteors. (1859–60.).”

The breakthrough that allowed us to identify the inspiration for Walt Whitman’s meteor imagery in Leaves of Grass came about a decade ago. We were reading Gerald Carr’s catalog for an exhibition of paintings by Frederic Edwin Church (1826–1900), an important figure in the group of American landscape painters known as the Hudson River School. The back cover of the catalog featured a canvas titled The Meteor of 1860, depicting a scene observed by the artist on July 20, 1860. It shows a group of fireballs, which we recognized as a meteor procession. The painting appeared most recently in a 2009 exhibition curated by Kevin Sharp at the Dixon Gallery, in Memphis, Tennessee. Our search through newspapers, scientific journals, and popular publications from 1860 turned up hundreds of eyewitness accounts of a “strange huge meteor procession” that exactly matched Walt Whitman’s description. The event also fell within the time period covered by his poem. On the evening of July 20, 1860, a large Earth-grazing body fragmented during its nearly horizontal passage through the atmosphere, creating a meteor procession

with multiple fireballs. The ground track covered at least 1,000 miles, from the Great Lakes through New York State to the Atlantic Ocean. Newspapers published stories from amazed citizens as far north as Middlebury, Vermont, and as far south as Washington, D.C., and Virginia. The July 23rd New York Tribune carried this report from an observer in Hunterdon County, New Jersey: A meteor of immense size, and casting a bright glare of light upon the earth, burst apparently from a cloud in the west, a little to the north, and, passing slowly and with uniform speed toward the east . . . it . . . moved so slowly and with such regularity. Its head resembled two large flaming stars, one close behind the other . . . leaving a long, brilliant streamer in its wake . . . Near the end of the tail were three red fire-balls, of different magnitudes . . . All these bodies moved as if connected by an invisible string, so perfectly did they keep their distances . . . it moved on in silence, and disappeared in the distance.

Most reports came from the general public, but such noted astronomers as C. H. F. Peters (Hamilton College Observatory, Clinton, New York), Ormsby McKnight Mitchel (Dudley Observatory, Albany, New York), Albert Hopkins (Williams College Observatory, Williamstown, Massachusetts), and George P. Bond (Harvard College Observatory, Cambridge, Massachusetts) also witnessed the great meteor. Mitchel described the event in the August 4th Harper’s Weekly: Two principal fragments, each followed by a train of light, and not more than two degrees apart, pursued an easterly course, while at the distance of about eight or ten degrees several smaller fragments, less brilliant than the first two, followed in a straight line . . . [traveling] just under the southern star Antares . . . and pursuing a line nearly horizontal it passed under the planet Mars . . . and continuing its course toward the east, it finally disappeared, while yet some eight or ten degrees above the horizon . . . the meteor faded out at fifty minutes past nine.

Visit SkyandTelescope.com/72fireball for more coverage of the 1972 daylight fireball.

meteor descended as it traveled from the Great Lakes through western New York, reaching a low point 39 miles above the Hudson River valley with a horizontal speed greater than escape velocity. It was ascending back into space as it crossed Long Island and continued out over the Atlantic Ocean. At Harvard College Observatory, Bond combined his own observations with records from other locations and likewise concluded in a letter to the New York Times that “the great meteor . . . instead of falling upon our globe, or being consumed . . . may have passed beyond the limits of the atmosphere, and resumed its original character as a wanderer in the planetary spaces.” The July 20, 1860 meteor apparently performed the same remarkable feat as the daylight fireball of August 10, 1972 — escaping back into space after a grazing encounter with Earth’s atmosphere. This year marks the 150th anniversary of the passage of the Great Comet in June and July 1860 and the meteor procession of July 20. These were spectacular celestial events during an anxious time in United States history, and they inspired the comet “flaring in heaven” and the “strange huge meteor procession” in Walt Whitman’s Leaves of Grass. ✦ Don Olson and Russell Doescher teach in the Department of Physics, and Marilynn Olson in the Department of English, at Texas State University, where Ava Pope is an undergraduate in the Department of Physics and the Honors Program. The authors are grateful to Evelyn Trebilcock, Valerie Balint, and Ida Brier at Olana State Historic Site in Hudson, N.Y., Shirley McGrath at the Vedder Research Library in Coxsackie, N.Y., and Margaret Vaverek at Texas State University’s Alkek Library.

Many reports, such as this one from Albany, New York (published in the July 23rd New York Tribune) mentioned the unusually slow motion, nearly parallel to the Earth’s surface: its course being horizontal . . . its velocity more majestic than swift . . . a more sublime spectacle than the meteor itself I never witnessed. Its light was first pale, then clear, then blue, amber, and purple.

James Coffin (Lafayette College, Easton, Pennsylvania) published a lengthy compilation in Smithsonian Contributions to Knowledge with more than 200 observations of altitude and azimuth that he used to calculate the meteor’s path through the atmosphere. Coffin concluded that the

S&T’s Roger Sinnott (left) joined authors (left to right) Russell Doescher, Marilynn Olson, Ava Pope, and Don Olson for a visit to Church’s home in Hudson, New York, while researching this article.



Serendipitous Amateur Finding

Deep-Sky Disc very EUREKA! Dave Jurasevich discovered the Soap Bubble Nebula (inside the yellow “O”) in this H-alpha image, taken on July 6, 2008 as part of a mosaic of the IC 1318 region in Cygnus. The nebula is extremely faint and embedded within a diffuse nebula, explaining why it went unnoticed for so long. This image covers an area 1.3° by 1.6°. The total exposure time was 4 hours.

“Have you found anythi anything new up there?” mike simmons & dave jurasevich An amateur astronomer unearths a new planetary nebula, hinting that more hidden jewels are lurking out there.

We’ve all heard this th question when people learn we’re amateur astronomers. Discoveries are rare, but they do occur. These “new” objects are usually something that really is new — a comet making its first pass through the inner solar system since the Stone Age, or a nova that flares up suddenly. But what about deep-sky objects that have gone undetected since Galileo aimed his telescope skyward 400 years ago? The heavens are vast, yet they have been pretty well picked over for these jewels. The heavenly vault has not yet been completely emptied, however, as one California astrophotographer recently discovered. Other amateurs are likely to make similar findings as they adopt new technologies, raising questions about how to handle such discoveries in the Internet Age.



Dave Jurasevich is one of the few modern-day amateurs to find a deep-sky object hiding in plain sight. Dave’s eureka moment came iin broad daylight on July 6, 2008. He had spent the previous previo night imaging from his usual site at the historic Mou Mount Wilson Observatory, where he serves as superintendent. superintenden Dave specializes in H-alpha deep-sky imaging. He h had taken eight 30-minute images for a mosaic of the IC 1318 region using a 160-millimeter 1 (6.3-inch) Astro-Physics refractor. While processing these images, Dave noticed a delicate, perfectly round, bubblelike object approximate approximately 4 arcminutes in diameter that was even more symmet symmetrical than the well-known Bubble Nebula (NGC 7635). With the oft-imaged Crescent Nebula (NGC 6888) lurking nearby, this area of Cygnus is well known to amateurs and professionals. But Dave didn’t recall seeing a reference D to this faint object, and it was just far enough from the Crescent to lie outside the t usual imaging field, an unremarkable area where it jjust might have gone unnoticed. Dave also knew his n narrow-band image, capturing the light of only one em emission line, might have recorded something that wouldn wouldn’t have stood out in previous images. He scrutinized the image closely, looking for an imaging artifact that might have caused the delicate appam rition. The faint smudge seemed to be a real object. The odds of a nebula escaping the notice of countless other photographers seemed remote, but Dave began to think that he might have something. Dave went online to check three different catalogs of hydrogen regions, searching for mention of something at the mystery object’s position. There was nothing. He scrutinized online images of the region looking for a faint smudge in the same location, but again found nothing. Even SIMBAD, the largest reference of known objects

LATER IMAGE Dave Jurasevich took this image of the nebula more than a year later, on July 29, 2009, using his 12.5-inch RCOS Ritchey-Chrétien reflector and an SBIG ST-10XME camera.

DAVE JURASEVICH

Eureka Moment

AMATEUR DISCOVERER Dave Jurasevich appears at his discovery telescope, an Astro-Physics 160 EDF apochromatic f/7.7 refractor. The night he found the Soap Bubble Nebula, the scope was fitted with an SBIG STL-11000M CCD camera and an Astrodon Tru-Balance H-alpha filter with a 6-nanometer passband.

from catalogs and surveys of all types, came up empty. Excited that the object might actually be unknown — and mindful that the first person to report something new is credited with the discovery — Dave fired off an e-mail to the International Astronomical Union’s Central Bureau for Astronomical Telegrams (CBAT). Now based at Harvard University’s Department of Earth and Planetary Sciences, CBAT has been the agency responsible for announcing discoveries since the 1880s. He had staked his claim, but there was still plenty of work ahead to prove that he had struck pay dirt.

Making It Official Online amateur forums were soon abuzz with talk of the new object, but not because news of Dave’s image had leaked out. Coincidentally, two other California amateurs, Mel Helm and Keith Quattrocchi, had spotted the same nebula while conducting an H-alpha survey of the region just 11 days after Dave took his image. Though preliminary, Dave’s earlier e-mail to CBAT would prove pivotal in laying claim to the discovery. Dave followed his discovery report with a full account: 42 pages covering everything the professionals would need to evaluate his claim. Along with SIMBAD’s comprehensive listing and suggestions from IAU experts, he had scoured 12 catalogs and photo surveys. He could see the object (just barely) on the digital version of the second Palomar Sky Survey, but like many objects in deep wide-field surveys, it had gone unnoticed. Dave’s list of references was exhaustive and the result seemed clear: No one had ever noted this object before. With his report in CBAT’s hands, Dave had entered a rare domain for amateurs. As his report circulated among the world’s leading planetary nebula experts, no lenience Sk yandTelescope.com July 2010 35



20h 10m

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Crescent Nebula

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SOAP BUBBLE’S SKY The black box shows the area covered by the image on page 34. The new nebula is at right ascension 20h 15.4m, declination +38° 03´ (2000.0). It’s a great target for astrophotographers, but don’t expect to see it in an eyepiece.

would be granted for his amateur status. He had prepared well, furnishing details of the discovery, the object’s location, size, and shape, the equipment used, imaging parameters, a list of references, and his justification for claiming a discovery. But he hadn’t prepared for the time it would take for the process to play out. CBAT announcements of transient phenomena such as comets and novae are made as soon as the initial observations are confirmed, allowing prompt follow-up studies. In Dave’s case there was time to scrutinize the report, ask questions, and even conduct further studies before passing judgment. No one was in a hurry — except Dave. When a new transient object such as a comet or nova is announced, others quickly take aim for follow-up studies. Dave’s object wasn’t going anywhere, so CBAT Director Dan Green forwarded Dave’s report to the IAU’s official catalogers of planetary nebulae, Luboš Kohoutek (Hamburg Observatory, Germany) and Agnès Acker (Strasbourg Observatory, France). Acker suggested one last infrared photo survey Dave had missed, and Dave was surprised to find the bubble on one of the survey images. But a check of the survey’s object list showed that it had been skipped over. That meant it was still unknown. Dave’s supplementary report on this survey added 10 more pages to his already voluminous discovery report. Kohoutek commented that a spectrum would be needed to classify it as a planetary nebula, but noted that it would

be difficult because of the nebula’s faintness. Research telescope time has yet to be acquired to obtain a spectrum, but Green decided to make the discovery official anyway. The CBAT announcement of PN G75.5+1.7 — the object’s new official designation — came on July 16, 2009, one year and 10 days after Dave first glimpsed the ghostly wisp. Though research data has yet to establish the object’s physical parameters with precision (or even verify its classification as a planetary nebula), Dave compared it to wellresearched planetaries to estimate that it has expanded to about 5 light-years in diameter since its central star died 22,000 years ago, some 5,000 light-years from Earth.

Future Discoveries Professionals and amateurs have since imaged the Soap Bubble Nebula, as it has informally come to be known, and it’s a good bet that many more small telescopes will target it in the years to come. It’s also likely that new discoveries such as Dave’s will occur with increasing regularity. With narrow-band imaging and advanced image-processing techniques now available to amateurs, giant telescopes are no longer required to tease faint objects from an intricate background of gaseous filaments. But it remains unclear what amateurs should do with such a discovery. CBAT’s mission remains, as stated on its website, to act as “the clearinghouse for new discoveries of comets, solar-system satellites, novae, supernovae, and other transient astronomical events.” Deep-sky objects are conspicuously absent from that list. In fact, Green would probably have passed on this result had Dave not done such a great job of preparing his report. Green says he’s since been flooded with “discoveries” of supposed planetaries that weren’t researched as carefully as the Soap Bubble Nebula. This is one lesson amateurs need to keep in mind: If you want professionals to take your work seriously, you have to do professional quality work. Don’t expect anyone to do the work for you! Despite the automated sky surveys that seem to scoop up all the new objects these days, amateur discoveries have not become an endangered species. Green says amateurs are still responsible for finding many new transient objects, unusual variable stars, and meteor showers. In fact, amateurs find more than 90% of novae in the Milky Way region, an area avoided by the pros. One out of 10 supernova reports come from amateurs.

PRO CE S SING THE IMAGE Dave Jurasevich acquired his discovery image using MaxIm DL software for camera control. He calibrated and processed the FITS files in CCD Stack. He employed a final non-linear DDP stretch to draw out the extremely faint Soap Bubble from its surrounding nebulosity, and applied the finishing touches in Adobe Photoshop using the Levels and Curves functions.



TRAVIS RECTOR (UNIV. OF ALASKA, ANCHORAGE) / HEIDI SCHWEIKER (WIYN) / NOAO / AURA / NSF

SOAP BUBBLE NEBULA This image of the Soap Bubble Nebula was taken by the Kitt Peak 4-meter Mayall Telescope on June 19, 2009 in H-alpha (orange) and O III (blue) narrowband filters. The nebula is about 4 arcminutes in diameter.

And amateurs are still finding comets despite the professional survey instruments that now grab so many (more than 1,700 in the last decade alone). New technology has helped amateur searchers as well; visual comet discoveries are now a virtually extinct species. Amateurs aren’t usually prepared to find a new deepsky object such as the Soap Bubble Nebula, but with new imaging methods and increasingly sophisticated equipment, it may happen more often. Dave was particularly well prepared for the gauntlet of research, reporting, and discussions that spanned a full year. His 30 years as a mechanical engineer building potentially hazardous chemical facilities had cultivated an appreciation for detail, careful observation, and stringent recordkeeping. Though not a professional, he was hardly a novice after 40 years as an amateur astronomer and six years of imaging. Ten years of interacting with professionals at Mount Wilson also helped.

What Should You Do? But what about others? What should you do if you find something new? How do you ensure that you’ll receive credit for your discovery?

The answers aren’t always clear-cut, and catalog searches are only the first step. It’s one thing to confirm that the object is unknown, and quite another to determine what it really is. That remains a task for the professional experts. For planetary nebula candidates, Acker recommends a number of procedures. Images in several wavelength regions can characterize the nebula and its central star, while spectra can help differentiate it from HII regions and distant galaxies. Kohoutek thinks a spectrum is essential for planetary nebula classification. But obtaining this data is still firmly in the professional arena, especially with an object as faint as the Soap Bubble Nebula. Few amateurs have professional contacts for followup studies such as these, but pro-am collaborations are increasingly bringing the resources of the two communities together. George Jacoby (WIYN Observatory) leads one such effort. He and other professionals rely on The Deep Sky Hunters, a dedicated team of amateurs who identify planetary nebula candidates on Digital Sky Survey images for follow-up. So far the team has found 97 such candidates, of which 60 appear to be probable or possible planetary nebulae (all are much smaller than the Soap Bubble Sk yandTelescope.com July 2010 37



A SOAP BUBBLE AND A CRESCENT Roland Christen acquired this image of the Crescent Nebula (upper right) and its surrounding area with an Astro-Physics 305-mm f/3.8 Astrograph and an SBIG ST-11000 camera. The Soap Bubble Nebula (arrowed) is just barely visible. The total exposure was about 5 hours through H-alpha, O III, and RGB filters.

Vis Dave Jurasevich’s website at Visit http://www.starimager.com. htt

Nebula). The amateurs share authorship on the scientific papers that are the traditional arbiters of discovery claims. The first in print usually receives credit for a discovery. But with papers taking two to three years for publication in peer-reviewed journals, other routes are needed in today’s world of instant communication. CBAT’s e-mail blasts are fine for transient objects, and other IAU groups handle a variety of other object types. Thus, after searching through catalogs, an amateur discoverer’s second task is to make inquiries and find the right agency to accept his or her report and engage the experts. Until astronomy research transitions to accommodate the amateur’s more active role, amateurs will still need to navigate their way through the labyrinthine professional world.

Fortunately, the universe won’t run out of surprises in our lifetimes. As increasingly well-equipped amateurs reach deeper into their vaults, they are bound to turn up more gems. If you’re among the successful treasure hunters, follow a tip from Dave Jurasevich and do your homework first. You want to make sure your potential diamond doesn’t belong to someone else, and that it’s not just a piece of glass. ✦ S&T contributing editor Mike Simmons is a life-long amateur astronomer based in southern California who has never found anything new. He is the Founder and President of Astronomers Without Borders. Dave Jurasevich is Superintendent of the Mount Wilson Observatory, allowing him the unique opportunity to combine his amateur astronomy hobby with the operational challenges of a professional scientific facility.



S&T: DENNIS DI CICCO / SEAN WALKER

As the accompanying article makes abundantly clear, the heavens still hold surprises for deep-sky observers. And the advanced imaging capabilities of today’s amateurs are opening the doors for discovering hitherto overlooked objects. For another example, consider the nebula pictured at right, which we found in Camelopardalis while working on a huge mosaic project last winter. Although the 20′-diameter nebula is very faint, the central grouping of stars can be seen in binoculars. To our eyes, it looks like a star cluster involved with a nebula, but it might be a chance juxtaposition of stars and a knot of nebulosity. After spotting the nebula on our mosaic we’ve also located it on various sky-survey images done at visual wavelengths, and it was apparently detected at infrared wavelengths by the IRAS spacecraft. Regardless, we can’t find the nebula or star grouping identified as such in any catalog. Here’s the short version of the background story. Last year we described our project to photograph the enormous Orion– Eridanus Superbubble (S&T: April 2009, page 65). The pictures with that story were our “test exposures” to map the structure that we could record from our suburban Boston location. This past winter we set about imaging the area in detail. The result is a 25-panel, 400-megapixel mosaic covering more than 6,000 square degrees of sky. It required more than 120 hours of exposure and an equal amount of time processing the data and assembling the mosaic (and we call this a hobby!). Much of the field is covered with a veil of faint nebulosity relatively unknown to observers and astrophotographers. But claiming any of these diaphanous whips as a discovery would be as ludicrous as claiming the discovery of individual waves in the ocean. Nevertheless, we have been searching the image

SHELDON FAWORSKI / SEAN WALKER

Another Deep-Sky Discovery?

Is it a star cluster in a nebula or just a chance alignment of stars and emission nebulosity? Regardless of its true nature, the object isn’t listed in any catalog known to the authors. This view was obtained with a 12-inch f/3.9 Newtonian astrograph, QSI 583wsg CCD camera, and exposures through hydrogen-alpha, red, green, and blue filters. North is up in this ½º-tall field.

for interesting “out-of-the-way” targets to photograph with longer focal lengths and/or deeper exposures. There are many, but the one above (first noted by Sean) stood out from others because we couldn’t identify it in any catalog. And its visual association with a group of relatively bright stars makes it even more intriguing. We are continuing to find out as much about it as possible. Meanwhile, readers interested in having a look for themselves will find this object at right ascension 4h 41.1m declination +57° 53′ (epoch 2000.0 coordinates). The central grouping of stars is easily spotted in binoculars, and the four brightest members can be resolved in large binoculars and small telescopes, looking a bit like a miniature version of the constellation Corvus. One of the four is even bright enough to be plotted on Sky & Telescope’s Pocket Sky Atlas. — Dennis di Cicco and Sean Walker The authors first noted the object (arrowed) in this panel from their mosaic described in the accompanying text. Capella is the brightest star at lower left, and the field is approximately 19º square with north up. It is a 4-hour exposure taken with an Apogee U16M CCD camera, Astrodon 3-nanometer hydrogen-alpha filter, and 110-mm f/2 Hasselblad lens stopped to f/4.



Fred Schaaf Northern Hemisphere’s Sky

Reading the Storybook Sky Star lore flowers in every time and place. Is there any storybook as great as the one we call the

AKIRA FUJII

sky? It’s literally the largest collection of tales, stretching from horizon to horizon. And those tales come from every culture and era, back into distant prehistory. What’s more, the sky is a picture book. And its stories are outlined in the flames of stars, a book written in heavenly fire. Tales of the Scorpius Hour. The collection of stories visible in the sky changes from hour to hour as our Earth rotates. We can call the sky scene depicted on our all-sky map (page 44) the Scorpius Hour — after the big, brilliant, curling Scorpion above the southern horizon. What legendary figures and tales are depicted in the sky at the Scorpius Hour? Tails of the Scorpius Hour. There are so many beasts and dangerous monsters in the sky now that we could spend a long time telling just the tales of their tails. The tail and stinger of Scorpius itself was, according to one myth, used to kill Orion the Hunter. The stinger is marked by a close pair of bright stars, but Scorpius’s chief light is the 1st-magnitude red giant at his heart: Antares.

Dazzling Scorpius curls above the southern horizon in early summer. Note Antares, the Scorpion’s brightest star, at center right and the twin blue stars of its stinger at center lower left. The bright star cluster upper left of the stinger is Messier 7.

Directly above Scorpius at this time is sprawling Ophiuchus, the Serpent Bearer, who separates Serpens, the only constellation that consists of two disjoint pieces. Serpens Caput (the serpent’s head) is west of the Bearer, while Serpens Cauda (the serpent’s tail) thrusts from Ophiuchus’s eastern edge into the great dark rift in the Milky Way band. What’s the most prominent tail in the sky? The 1stmagnitude star Deneb, which marks the tail of beautiful Cygnus, the Swan. Deneb means “tail” in Arabic, and the root is found in many other star names. For instance, Leo’s second brightest star is called Denebola, meaning Tail of the Lion. In the north and northwest sky, the unnaturally long bear tails of Ursa Minor and Ursa Major now point straight down and almost straight up, respectively. The rather faint tail of twisting Draco, the Dragon, runs between the bears, with Draco’s compact head facing brilliant Vega. A tale that’s less well known is that the Coma Berenices star cluster originally marked the tuft of Leo’s tail. (Coma is Latin for “hair.”) It was renamed around 245 BC to honor Queen Berenice II of Egypt. Stories ancient and modern. Many of the constellations are extremely old. Some astronomy historians think that the Great Bear may go back at least 12,000 years, to the last Ice Age. Capricornus, now rising in the southeast, is part goat and part fish — the unique form of the Sumerian god Ea, who was popular more than 4,000 years ago. Myths of ancient Greek heroism and music-mastery are commemorated high in our Scorpius Hour sky by the constellations of Hercules and Lyra (the lyre of Orpheus). The protagonists of one great, old, Chinese star myth are already high in the east: Vega (or Lyra), the Weaving Maiden, and Altair (or the three-star line centered on it), the Prince or Cowherd. But not all sky stories and pictures are old; new ones are still being invented. The Summer Triangle of Vega, Altair, and Deneb only became popular about 50 years ago. Even more recently, the ancient centaur pattern of Sagittarius was largely supplanted by the Teapot asterism of Sagittarius’s brightest stars. ✦ Fred Schaaf welcomes your comments at [email protected].



FOCUS ON

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Cosmic Trails

During Our Trip: TOTAL LUNAR ECLIPSE Tuesday, December 21, 2010

Cruise prices start at $999, per person, for an Inside Stateroom. For those attending our seminars, there is a $1,275 fee. Taxes are $244.23 per person. Port Charges and an InSight Cruises service fee are $245. For more info contact Neil at 650-787-5665 or [email protected]

DECEMBER 13 – 23, 2010

www.InSightCruises.com/Sky

Listed is a sampling of the 19 sessions you can participate in while we’re at sea. For a full listing visit

www.InSightCruises.com/Sky-talks

CURIOUS ABOUT THE BEAUTY OF THE NIGHT SKY AT SEA? Game to explore facets of the moon, then take in a total lunar eclipse in the company of kindred spirits? Gather astronomy knowledge on a new wavelength aboard Cosmic Trails, December 13–23, 2010, on Holland America Line’s m.s. Zuiderdam. Journey with Sky & Telescope into the Panama Canal, whose engineering is the product of an historic struggle against Nature and skepticism. You’ll get a behind-the-scenes look at the Apollo program; explore the road less traveled in the winter sky; see beyond the obvious, into the mysteries of the Moon; bring home an insider’s techniques, tips, and tricks for getting the most out of lunar observation; and learn astrophotography details from basic to cutting edge. While you’re in balmy tropical climes, kayak with your companion through crystal blue Aruban waters and venture into Costa Rica’s rainforests, surrounded by the sounds of birds and the colors of flora and fauna. Indulge your thirst for knowledge. Sail with Sky & Telescope and indulge your thirst for knowledge. Relax with a friend; enjoy fun and camaraderie with fellow astronomers; rekindle a longdormant fascination with the cosmos. Visit www.InSightCruises.com or call Neil or Theresa at 650-787-5665 to get all the details, and then enrich your astronomy routine with an intellectual adventure with the Sky & Telescope community.

Origin of the Moon — Although there are many ideas for how our Moon came to exist, only one makes sense chemically and physically: The Moon came from a Big Splash, the molten and vaporized rock that is ejected during a giant impact on Earth by a body about the size of Mars. I will describe how this not only explains the Moon but also sets the stage for all of subsequent Earth evolution. Speaker: David Stevenson, Ph.D.

America the Beautiful at Night — It’s truly amazing results one can achieve with Landscape Astrophotography using just a tripod and 35mm camera with a standard lens. Whether you are a novice astrophotographer or an advanced imager, you will be amazed at the simplicity and beauty that you can obtain using basic equipment and a little know how. Speaker: Walter Pacholka Capturing the Light: The Night Sky — In this session we’ll cover all the basic techniques in capturing the night sky: cameras, lenses, exposure times, and camera setting as well as Landscape Astrophotography equipment that is good, better, and best for the budget imager or cutting-edge imager. By then end of this talk you’ll understand the difference between what the eye sees and what the camera sees — and how to use this knowledge to make great photos. Speaker: Walter Pacholka

Viewing and Understanding the Moon — When is the best time to view the Moon? What kinds of features can I see? Where is the best place to look? These are just some of the questions answered in this talk. But perhaps Naked-Eye Astronomy — Contrary to popular opinion, you can enjoy a lifetime of astronomy with little most rewarding is developing an understanding of what it is you’re seeing in your telescope. How did this crater or no equipment other than your unaided eye. Learn to explore the constellations and see colors in the stars. Find form? Why does it look this way? Why are some parts of out how to spot the International Space Station passing the Moon bright, and others dull? Why are some smooth, across your sky or watch the brilliant flash of an Iridium while other regions a jumble of craters? Equipped with a satellite. Know when to look for gatherings of the Moon telescope and armed with the information presented in this talk, you can explore the Moon like a lunar geologist. and planets. Look for Sun dogs, Sun pillars, and radiant Speaker: Gary Seronik crepuscular rays. These and many more celestial wonders can be viewed by those who know where and when to Winter-Sky Wonders — For many of us, this is the look. Speaker: Sue French coldest time of the year — but it also harbors the most Telescopes for Stargazing — A backyard telescope is a wonderful thing. But with the bewildering variety of equipment available today, it’s difficult for the budding astronomer to know what best suits his or her needs. A lot can be done at modest expense, while some fairly expensive telescopes can be quite frustrating. Learn about the different types of telescopes, and what they are best suited for. Find out what accessories are essential, and which can wait. Discover how you can test drive telescopes and some of the equipment that goes along with them, as well as how to look for help when you need it. Speaker: Sue French Exploring the Night Sky with Binoculars — Just about every one associates stargazing with telescopes — but even the most experienced backyard astronomer owns binoculars. But not all binoculars are created equal. In this talk Gary will tell you how to choose and use binoculars specifically for viewing the night sky. He also describes tips and tricks to help you get the most out of your viewing experiences. Finally, Gary lists the Top 10 binocular sights you can view while on our cruise. Speaker: Gary Seronik

brilliant stars and some of the most spectacular wonders of the deep-sky. They include nebulae, clouds of gas and dust either glowing by their own light or reflecting the light of nearby stars; clusters of stars, both old and young; galaxies far beyond our own; multiple stars; and variable stars. And if that’s not enough, we also have intricate Jupiter in our evening sky and awe-inspiring Saturn in the morning! Speaker: Sue French

Apollo Astronaut Experience — Only 24 men have been to the moon. While researching his landmark book, A Man on the Moon, Andrew Chaikin spent more than 150 hours interviewing 23 of the 24 Apollo lunar astronauts about every aspect of their incredible journeys. Chaikin will share anecdotes and insights from this extraordinary handful of men, the only humans to visit another world. Speaker: Andrew Chaikin

THE KENNEDY SPACE CENTER: AN INSIDER’S VIEW NASA’s launch headquarters, on the Space Coast, is the only place on Earth where you can tour launch areas, meet a veteran astronaut, and grasp the true enormity of the Space Program. Experience fun and wonder with Cosmic Trail companions in this private pre-cruise, custom, full-day tour. Get ready to walk among and beneath giant rockets, discover what it takes to launch the Space Shuttle from preparation to liftoff, and soak in Kennedy Space Center’s “The Right Stuff ” vibe. We’ll have an intense day with our expert guides, integrating the touchstones and experiences every visitor wants with behind-the-scenes sites seldom accessible to the public. The LC 39 Observation Gantry,

International Space Station Center, Apollo/Saturn V Center, and Astronaut Hall of Fame are on the agenda. We will not only view but visit the Vehicle Assembly Building, the shuttle landing strip, and the 6-millionpound crawler that transports the shuttle. Do lunch with an astronaut, view IMAX films with footage shot during NASA missions, and enjoy the products of mankind’s inspiration. The Kennedy Space Center excursion is $225; it includes all of the above plus dinner, and transportation from the Kennedy Space Center to our pre-cruise hotel in Ft. Lauderdale. For details/questions, please contact Neil or Theresa, or give us a call at (650) 787-5667.

As we sail away from Fort Lauderdale, Florida, we’ll kick off Cosmic Trails with observation of the GEMINIDS METEOR SHOWER.

© Wally Pacholka / AstroPics.com


July 2010

Sky at a Glance 4

LAST-QUARTER MOON (10:35 a.m. EDT). Jupiter is about 10° lower right of the Moon before and during dawn.

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PREDAWN: The Pleiades star cluster is 1° to 3° above the thin crescent Moon as the sky starts to grow light in North America, a lovely sight to the unaided eye and in binoculars. Look for them in the east at least an hour before sunrise.

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NEW MOON (3:40 p.m. EDT). A total solar eclipse is visible in the South Pacific; for details see SkyandTelescope.com/eclipses.

14, 15 DUSK: The thin crescent Moon is about 7° lower left of Venus on the 14th. A somewhat fatter crescent is a similar distance lower left of Mars on the 15th.

PLANET VISIBILITY ◀ SUNSET

DUSK: Regulus is about 1° lower left of Venus on the 9th and 1° below Venus on the 10th, as shown on page 48.

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29, 30 DUSK: Mars is less than 2° below Saturn, as shown on page 49.

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PLANET VISIBILITY SHOWN FOR LATITUDE 40o NORTH AT MID-MONTH.

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NIGHT: Jupiter rises roughly 6° lower right of the waning gibbous Moon around 11 p.m. daylight-saving time in North America.

The light of venus reflects off the English Channel, with fishing boats and cloud banks in the distance.

IMAGE BY PETE, RICHARD, & D O U G L A S L AW R E N C E


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S ARIU AQU

S N ) E T P U R P E A S C (

B

A

A

5

20h

Y

B

C R

D

US

C

DE

A

D

M2

SE

D

ig

Polaris

D

CYG N

G

Nort h e r n VU M29 C r o ss M27

E

G

Z

E O

T

g

i

pp

52 A

61

Q

–1

B

URSA MINOR

er

M

Deneb

M39

TA

M15

E

M13

HERCULES

B

A

G

ER

H

H

P

B

SA

L

B A

A

LA C

B

P E GA SU S

Z

Zenith

+20°

TU

M

M8

1

M8

E D A M

A

M Jul oon y2 5

U M R A S JO A R

O M

A

Great S q uare of Pega sus

h

23

Facing East

M92

G

C

E

N

14h U S R U TA

g

in c Fa

Using the Map

Binocular Highlight:

WHEN

Riding the Scorpion

Late May

2 a.m. *

Early June

1 a.m. *

Late June

Midnight *

Early July

11 p.m.*

Late July

Dusk

N

W

A

*Daylight-saving time

Q

Ven u

s

D

O LE

G

O LE OR N I M

HOW

h

Example: Rotate the map a little so that “Facing SE” is at the bottom. About halfway from there to the map’s center is the bright star Altair. Go out, face southeast, and look halfway from horizontal to straight up. There’s Altair!

H

D

Sa

B

tu

rn

M

ars

B

Facing West

11

Go outside within an hour or so of a time listed above. Hold the map out in front of you and turn it around so the yellow label for the direction you’re facing (such as west or northeast) is at the bottom, right-side up. The curved edge is the horizon, and the stars above it on the map now match the stars in front of you in the sky. The map’s center is the zenith, the point overhead.

L

I

P

T

G

I

C

Note: The map is plotted for 40° north latitude (for example, Denver, New York, Madrid). If you’re far south of there, stars in the southern part of the sky will be higher and stars in the north lower. Far north of 40° the reverse is true. The planets are positioned for mid-July.

C

CO

n oo 7 M ly 1 Ju

D

RV U

S

E

On warm summer evenings, the most globular-cluster-rich swath of Milky Way arches across the meridian. If you’re working your way through the Messier list with binoculars, this is a golden opportunity to pick up some new finds, including some neglected globulars. Both M19 and M62 are often overlooked — partly because they reside in a kind of no man’s land in the southern reaches of Ophiuchus. Indeed, it might be more useful to think of them riding on the back of Scorpius, the mythical Scorpion. Begin by locating Theta (θ) Ophiuchi, a 3.2-magnitude star some 12° east of Antares, the Scorpion’s pulsing red heart. Move Theta to the eastern edge of your binoculars’ field of view, and M19 will enter on the opposite side. This 6.8-magnitude globular is accompanied by a trio of bright, equally spaced, wide doubles situated north, northeast, and east of the cluster. It’s a strikingly attractive sight. M19 itself is obviously non-stellar in my 10×50s, and I was able to see it in my 10×30 image-stabilized binoculars. Move M19 to the top of your binocular field of view and nearby M62 will appear at the bottom. I suspect M62 will give you more trouble than its northerly neighbor because its core is stellar and has little of the typical globular “fuzz” surrounding it. At magnitude 6.2, M62 is brighter than M19, but you do have to look carefully to see that it’s not simply a field star. I was pretty certain I’d swept it up in my 10×30s; however, it took the magnification boost provided by my 15×45 image-stabilized binos for me to confidently confirm the sighting. This pair of Messiers demonstrates an important consideration when it comes to viewing globulars in binoculars — often it’s not the overall brightness of the cluster that matters so much as how the brightness is distributed. ✦ — Gary Seronik OPHIUCHUS

B

Q

5°

bino

cular vie

g

SW

G

ci Fa

n

Galaxy

You can create a star chart that’s customized for any location, date, and time at SkyandTelescope.com/ skychart.

w

Antares

M19

A T M62

Double star Variable star

SCORPIUS

Open cluster Diffuse nebula Globular cluster Planetary nebula

E Sk yandTelescope.com July 2010 45


Planetary Almanac

Sun and Planets, July 2010

Mercury

11

July 1

21

July

31 Sun

Right Ascension

Magnitude

Diameter

Illumination

Distance

––

–26.8

31′ 28″

––

1.017

+18° 23′

––

–26.8

31′ 31″

––

1.015

6 52.7

+24° 23′

3° Ev

–2.0

5.1″

99%

1.326

11

8h 20.3m

+21° 25′

14° Ev

–0.8

5.3″

87%

1.258

21

9h 30.0m

m

+23° 08′

h

m

1

h

m

1

Venus

6 38.9

31 Mercury

1

31

16

8 39.9

Venus

1

16

31

Jupiter

+15° 57′

22° Ev

–0.2

5.9″

72%

1.132

m

+9° 48′

26° Ev

+0.1

6.8″

59%

0.989

1

h

9 28.4

m

+16° 48′

40° Ev

–4.1

15.5″

71%

1.077

11

10h 12.1m

+12° 40′

42° Ev

–4.1

16.7″

67%

1.001

21

10h 53.3m

10 22.6

+8° 05′

44° Ev

–4.2

18.1″

63%

0.924

h

m

+3° 14′

45° Ev

–4.3

19.7″

59%

0.845

1

h

10 57.9

m

+7° 36′

64° Ev

+1.3

5.2″

91%

1.793

16

11h 29.7m

+4° 01′

58° Ev

+1.4

4.9″

92%

1.895

31

12h 02.5m

31 Mars

Jupiter

16

Saturn

11 32.2

+0° 15′

53° Ev

+1.5

4.7″

93%

1.988

h

m

–0° 12′

96° Mo

–2.5

41.5″

99%

4.749

31

h

0 13.9

m

–0° 04′

124° Mo

–2.7

45.6″

99%

4.319

1

11h 58.2m

+2° 44′

80° Ev

+1.1

17.2″

100%

9.661

31

12h 05.9m

1

Saturn

Uranus

Elongation

h

31

Mars

Declination

h

0 11.0

16

+1° 47′

53° Ev

+1.1

16.4″

100%

10.113

h

m

–0° 33′

113° Mo

+5.8

3.6″

100%

19.677

h

m

0 02.7

Neptune

16

22 01.5

–12° 36′

145° Mo

+7.8

2.3″

100%

29.179

Pluto

16

18h 14.5m

–18° 19′

160° Ev

+14.0

0.1″

100%

30.911

16 The table above gives each object’s right ascension and declination (equinox 2000.0) at 0 h Universal Time on selected dates, and its elongation from the Sun in the morning (Mo) or evening (Ev) sky. Next are the visual magnitude and equatorial diameter. (Saturn’s ring extent is 2.27 times its equatorial diameter.) Last are the percentage of a planet’s disk illuminated by the Sun and the distance from Earth in astronomical units. (Based on the mean Earth–Sun distance, 1 a.u. is 149,597,871 kilometers, or 92,955,807 international miles.) For other dates, see SkyandTelescope.com/almanac.

Uranus Neptune Pluto

2h

4h

6h

Planet disks at left have south up, to match the view in many telescopes. Blue ticks indicate the pole tilted toward Earth.

0h

20 h

22h

18h

+30° GEMINI

7 ECL

+10°

TAURUS

Betelgeuse Procyon

IPT

4 IC

–10° –20°

Jupiter

–30° –40°

Rigel

Sirius

ER ID ANU S

HERCULES

Venus OPHIUCHUS

Uranus

1

VIRGO

July 25–26

LIBRA

Pluto CAPR ICORN U S

2 am

Spica

CORVUS

17

21

SAGITTARIUS Midnight

H Y D R A

SCORPIUS 10 pm

8 pm

6 pm

+10°

Regulus

14

Antares

Fomalhaut

LOCAL TIME OF TRANSIT 8 am 6 am 4 am

Saturn

Mars

E Q U AT O R

AQUARIUS

Neptune

Pollux

Mercury

LEO

Arcturus

A Q U ILA

31

CETUS

CANIS MAJOR 10 am

8h +30°

PISCES

ORION

10 h

14 h 12h RIGHT ASCENSION

CYGNUS

ARIES PEGASUS

0°

16 h BOÖTES

Vega

Castor

4 pm

0°

DECLINATION

+40°

10"

2 pm

The Sun and planets are positioned for mid-July; the colored arrows show the motion of each during the month. The Moon is plotted for evening dates in the Americas when it’s waxing (right side illuminated) or full, and for morning dates when it’s waning (left side). All dates are in July. “Local time of transit” tells when (in Local Mean Time) objects cross the meridian — that is, when they appear due south and at their highest — at mid-month. Transits occur an hour later on the 1st, and an hour earlier at month’s end.



–10° –20° –30° –40°

Jupiter’s Moons

Saturn’s Moons

July 1

July 1

2 3

EAST

WEST

Callisto

2 3

4

4

5

5

6

6

7

7

8

8

Ganymede

9

10

11

11

12

12

13

13

14

14

15

15

16

16

Io

Rhea

Enceladus Titan

17

18

18

19

19

20

20

21

Europa

WEST

9

10

17

EAST

Tethys

21

22

22

23

23

24

24

25

25

26

26

27

27

28

28

29

29

30

30

31

31

Dione

The wavy lines represent major satellites of Jupiter and Saturn. The central vertical lines represent Jupiter (left) and Saturn and its rings (right). Each gray or black horizontal band is one day, from 0 h (upper edge of band) to 24h UT (GMT). The UT date is given at left. Slide the edge of a piece of paper down to your date and time, and read across to see the satellites’ positions east or west of the planet at that time.


Fred Schaaf Sun, Moon, and Planets

Celestial Soiree Four of the five bright planets gather at dusk in the second half of July. The total solar eclipse of July 11th brings daytime darkness to the South Pacific but only a few land areas; see SkyandTelescope.com/eclipses for details. Throughout July, however, a dramatic contracting line of evening planets is visible around the world.

EVENING At nightfall on July 1st, Saturn, Mars, and Venus are strung in the west in a 38°-long, downward-slanting line. Two weeks later the line has shrunk to 24°. And by July 31st the line has become a very skinny triangle with Mars and Saturn less than 2° apart at the left and Venus 7½° to their lower right. Unfortunately, these planets appear fairly low to observers at mid-northern latitudes — about 15° above the horizon an hour after sunset by month’s end. Furthermore, while Venus shines resplendently around magnitude –4.2, Saturn is only +1.1 and Mars about +1.5.

Still, the drama of Mars closing in on Saturn and Venus closing in on both of the others is undeniable — especially because the action also includes two 1stmagnitude stars and, in the second half of the month, a fourth planet. The left (eastern) end of the threeplanet line can be extended roughly 25° to Spica. Regulus lies within the line until Venus passes it on July 9th and 10th; after that, Regulus forms an extension on the right-hand side of the line. And Mercury becomes visible to Regulus’s lower right sometime in mid-July. Mercury remains bright throughout this apparition, though it fades gradually from magnitude –0.5 at mid-month to magnitude +0.1 at month’s end. It stays quite low; viewers at latitude 40° north see it highest (7° above the west-northwest horizon a half hour after sunset) on July 26th, a remarkable 12 days before its greatest elongation from the Sun.

Dusk, July 1

Three fascinating conjunctions take place among these planets and stars. First, on the American evenings of July 9th and 10th, Venus passes a bit more than 1° above Regulus, which is 150 times fainter. They’re within 3° of each other from July 7th through 12th. Telescopes show Venus growing to 20″ wide this month while its gibbous phase wanes to about 60% lit. Mercury begins to appear very low in the sunset toward the middle of July. It’s less than ½° lower left of Regulus on the American evening of July 27th. Use binoculars to look for the pair about two fist-widths at arm’s length lower right of bright Venus. Mercury is fading but still outshines Regulus by far. The third conjunction is the meeting of Mars and Saturn, also near the end of the month. They’re within 2° of each other from July 29th through August 1st and are closest, less than 1.8° apart, on the evening of July 30th. In telescopes Mars is Denebola

Dusk, July 9 1 hour after sunset

1 hour after sunset

Saturn

H Mars

Sickle of LEO 10o

Mars H

LEO

Regulus Venus Venus Regulus

Looking West

Looking West



1.1o apart!

December solstice

ORBIT S OF THE PL ANE T S The curved arrows show each planet’s movement during July. The outer planets don’t change position enough in a month to notice at this scale.

Mercury

March equinox

Earth

Venus

Mars

June solstice

now just 4.7″ across, less than one-third as wide as Saturn’s globe and one-seventh as wide as Saturn’s slowly opening rings.

THE REST OF THE NIGHT Jupiter, in dim Pisces, rises around the time Saturn sets: a little after midnight (daylight-saving time) at the start of July, but around 10:30 p.m. by month’s end. Jupiter is a grand sight for both naked eye and telescopes, brightening in July from magnitude –2.5 to –2.7 as its disk increases to more than 45″ wide. For the past five years, Jupiter has been low in the sky for northern observers, but it nudges briefly north of the celestial equator from July 8th to 30th. With telescope or binoculars, look 2° to 3° west of Jupiter for 6th-magnitude Uranus; you can identify it with the finder chart at SkyandTelescope.com/uranus. Jupiter begins retrograde motion (westward against the background stars) on July 24th and will catch retrograding Uranus for a conjunction in September. Pluto is now a prime telescopic target in the middle of the night, as discussed on page 60. Neptune is best observed in the pre-dawn hours; for a detailed chart see SkyandTelescope.com/neptune.

MOON, SUN AND EARTH The waning crescent Moon is 1° to 3° below the Pleiades an hour or more before sunrise on July 8th in North America — a lovely sight to the naked eye and in binoculars. The waxing crescent Moon passes 6° to 7° below the contracting line of evening planets on July 14th and 15th, as shown at right. And around 11 p.m. daylight time on July 30th, Jupiter rises about 6° lower right of the waxing gibbous Moon. The Sun is totally eclipsed by the Moon over the South Pacific on July 11th; see SkyandTelescope.com/eclipses. Earth is at aphelion, its farthest from the Sun for the year, at 7 a.m. EDT on July 6th. The distance then is 94,508,000 miles, 1.67% farther than average. ✦

Sept. equinox

Sun

Saturn

Uranus Jupiter Neptune

FPO

Pluto

These scenes are drawn for near the middle of North America (latitude 40° north, longitude 90° west); European observers should move each Moon symbol a quarter of the way toward the one for the previous date. In the Far East, move the Moon halfway. The blue 10° scale bar is about the width of your fist at arm’s length. For clarity, the Moon is shown three times its actual apparent size.

Dusk, July 31 45 minutes after sunset

Saturn Mars Venus

Mercury Regulus

Looking West

Dusk, July 13 –16

Denebola

45 minutes after sunset Saturn Moon July 16

Mars Moon July 15 Venus Moon July 14

Regulus

Moon July 13

Mercury

Looking West Sk yandTelescope.com July 2010 49


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Charles A. Wood Exploring the Moon

Touring Soviet Landing Sites LRO reminds us of the great Soviet accomplishments on the Moon. Since entering orbit in June 2009, NASA’s Lunar Reconnaissance Orbiter (LRO) cameras have snapped thousands of ultra-high-resolution images of the Moon’s surface, revealing tiny features as little as 20 inches (50 centimeters) across. But the observations that have really captured the public’s interest are the images of spacecraft that reached the Moon. Finally, we can show the skeptics new pictures of the Apollo landing modules, equipment deployed by astronauts, and even their trails of footsteps where they walked 40 years ago. These hyper-resolution views pinpoint exactly where spacecraft landed on the Moon, and also provide better geologic context to the

pictures they took and the samples they returned. This is especially valuable for the Soviet missions, whose landing locations were often uncertain at best; LRO has already imaged some. Mission scientists hope to find them all. This new information also makes it timely for observers to hunt down the areas where these Soviet relics reside. Their locations are far less familiar than the Apollo landing sites, but no less historically important. At least 18 Soviet spacecraft landed on the Moon, either by crashing, such as Luna 2 (the first spacecraft to impact another world), or through w carefully controlled c

YURI GORYACHKO / MIKHAIL ABGARIAN / KONSTANTIN MOROZOV; INSET: NASA / GSFC / ARIZONA STATE UNIVERSITY

Although immensely overshadowed by NASA’s Apollo missions, the Soviet Union successfully reached the Moon 18 times between 1959 and 1976. Cameras aboard the Lunar Reconnaissance Orbiter have located a number of Soviet craft, such as Luna 17 and its Lunokhod 1 rover (inset). The locations of Luna 9 and Luna 13 are also plotted on the image below.

Promontorium Heraclides Luna 17

Seleucus

Luna 13

Galilaei Luna 9



Exploring the Moon landings. Some of these ambitious Soviet accomplishments remain unmatched by NASA. There were three classes of successful Soviet landers. Luna 9 and 13, launched in January and December 1966, respectively, were the first vehicles to survive landing on the surface. Like most early lunar missions, the location for their landing was less important than their survival. Luna 9 touched down along the western shore of Oceanus Procellarum, south of the crater Galilaei. The photos it beamed back to Earth show a pebbly surface sprinkled with small craters and boulders. Luna 9 proved that the lunar surface could support a spacecraft — it didn’t sink into layers of dust. It’s easy to find the general area where human hardware first landed safely, but LRO’s cameras have yet to spot the exact position. Luna 13 landed on a mare plain that looks very similar to the Luna 9 area, southeast of the crater Seleucus. Luna 13 reinforced the idea that maria were safe landing zones. In 1970 Luna 17 landed about 30 miles (50 kilometers) southwest of Promontorium Heraclides, the headland of Sinus Iridum that juts into northern Mare

Imbrium. This region is easy to fi nd and observe, but you won’t find any distinctive features on this flat mare plain. Luna 17 carried Lunokhod 1, an ungainly looking wheeled contraption that functioned remarkably well. This lunar rover slowly drove across the lunar surface, remotely controlled by operators near Moscow. Lunokhod 1 traveled through a region littered with craters tens of feet across, often with boulders strewn along their rims. For the next million years, 6 miles (10 km) of rover tracks will commemorate the first drive on another world. Luna 21, carrying the Lunokhod 2 rover, touched down in early 1973 on the floor of le Monnier, a flooded crater filled with mare lavas that spilled over from Mare Serenitatis. The landing area near the southern rim of the crater has one feature just barely visible from Earth — a narrow trough that the Russians named “Straight Rille.” This rille is perhaps the most dramatic feature imaged by the Soviet lander missions, with each side of the trough exposing boulders, and a gentle valley between them. As you observe this area, think of the plucky rover that traveled south to see the crater rim, and remains parked on the surface at the end of its twin tread tracks. It covered 23 miles (37 km) of lunar terrain.

le Monnier

YURI GORYACHKO / MIKHAIL ABGARIAN / KONSTANTIN MOROZOV; LUNAR INSETS: NASA / GSFC / ARIZONA STATE UNIVERSITY (4)

Luna 21

Luna 21 and its well-traveled rover Lunokhod 2 (top left inset) landed in the flooded crater le Monnier, west of Mare Serenitatis. Three other Soviet lunar probes reside in the eastern quadrant of the Moon: Luna 24 in Mare Crisium, Luna 20 , which touched down on ejecta from the Crisium Basin, and Luna 16 within Mare Fecunditatis.

MARE CRISIUM

Luna 24

Luna 20

Luna 16

Naonobu



The third class of Soviet era landers are sample-return missions. These were the Soviet Union’s most ambitious attempts to return lunar samples to Earth before Apollo 11. Two sample-return missions failed before Apollo 11’s success, followed by another three. Finally, the robotic missions Luna 16 (1970), 20 (1972), and 24 (1976) succeeded, bringing 0.7 pound (0.3 kg) of lunar soil samples back to the motherland. Despite the tiny amount of returned material, these samples yielded detailed measurements of their ages and compositions. All three landings were near southern Mare Crisium, providing sample information far to the east of the regions visited by the Apollo astronauts. Luna 16 landed “blind” at night among the mare ridges north of the crater Naonobu in Mare Fecunditatis — its

lamps malfunctioned, so no pictures from the surface were possible. Luna 16 became the first fully automated spacecraft to return samples from another world. Luna 20 touched down south of Mare Crisium, roughly 60 miles north of Luna 16. Although this is a highland area, images returned by Luna 20’s camera suprisingly depict a relatively smooth landscape. The final spacecraft to reach the Moon during the Apollo–Luna era was Luna 24, landing within southern Mare Crisium. The sample of soil returned from Luna 24 imply the region was flooded by multiple events. You can see all three of these landing areas in a high-magnification view. Have a look for yourself! ✦ For a daily lunar fix, visit contributing editor Charles Wood’s website: lpod.wikispaces.com.

The Moon • July 2010 Highlighted Mission

Location

Coordinates

A

Luna 9

Oceanus Procellarum

8°N, 64°W

Oceanus Procellarum

19°N, 62°W

B

Luna 13

C

Luna 16

Mare Fecunditatis

D

Luna 17

Mare Imbrium

E

Luna 20

South of Mare Crisium

F

Luna 21

le Monnier (crater)

26°N, 30°E

G

Luna 24

Mare Crisium

12°N, 62°E

1°S, 56°E 38°N, 35°W 4°N, 56°E

Phases Last quarter New Moon First quarter Full Moon

July 4, 14:35 UT July 11, 19:40 UT July 18, 10:11 UT July 26, 1:37 UT

18 D

20 F

B

Distances

G E

A

Apogee 251,677 miles

July 1, 10h UT diam. 29′ 45″

Perigee 224,386 miles

July 13, 11h UT diam. 32′ 5″

Apogee 252,248 miles

July 29, 00h UT diam. 29′ 19″

C

8 Hausen (crater) Mare Orientale Compton (crater) Mare Humboldtianum

July 5 July 8 July 18 July 20

July 5

For key dates, yellow dots on the map indicate what part of the Moon’s limb is tipped the most toward Earth by libration under favorable illumination.


S&T: DENNIS DI CICCO

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S & T Test Report

Gary Seronik

A New Astroscanner One of astronomy’s most enduring and distinctive-looking telescopes gets an upgrade.

The “new and improved” Astroscan. You can be forgiven for thinking that this is the same ol’ scope Edmund Scientific has been making for more than three decades — most of the changes are subtle. The obvious ones involve the red-dot finder and a slip-on dew shield.

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production for more than 30 years? Okay, you got the Questar and Celestron’s Schmidt-Cassegrains — those are gimmes. But I’ll bet not many of you had Edmund Scientifc’s Astroscan on the list. Realizing that the Astroscan has been around for more than 30 years has made this stargazer feel a little old. I vividly recall seeing the first advertisement for the (then unnamed) curiously shaped scope WHAT WE LIKE: in the September 1976 issue of this Easy to use magazine. “A star is born . . . name Excellent documentation package it, win it!” ran the ad copy. Good choice of accessories The Astroscan’s bright red color WHAT WE DON’T LIKE: betrays its ’70s origins, yet the Not suited for high magnification scope has managed to avoid acquiring a “retro” patina. That’s because it’s never left the marketplace — nostalgia requires an absence to develop. And like the legendary Questar, if you compare the current Astroscan to the ’76 original, you’d be hard pressed to see any significant differences. That speaks well of the scope’s design — it has endured because its fundamentals are sound.

G A RY

Pop quiz: What telescopes have been in continuous

Getting Reintroduced So what is an Astroscan? Its distinctive red ABS plastic shell houses conventional Newtonian optics — albeit with a fast primary mirror and a window in place of a spider to support the secondary mirror. The scope’s defining feature, however, is its mount. The Astroscan was the first commercial telescope to use a ball-and-socket design



Simple but effective is a fitting description of the Astroscan’s focuser. The new version is subtly improved with the addition of a Teflon coating for a smoother focusing action (left). A nice feature of the scope’s front dust cap is that it can be used both with and without the dew shield in place (center). Eschewing the original’s metal peep sight, the new Astroscan features a unit-power, red-dot finder. Like most budget models, this finder suffers from an overly bright LED that can overpower faint targets (right).

— the spherical body of the scope simply rides on three felt pads affi xed to a rigid aluminum base. The new Astroscan (the “plus” model) reviewed here is essentially the 1976 instrument with a few evolutionary changes. Most obvious is the inclusion of a plastic dew shield. This tube extension helps slow the formation of dew on the scope’s optical window — a problem that plagued the original Astroscan. A nice feature of the dew shield is that it accepts the scope’s dust cap, so you can just leave the dew shield attached to the scope all the time. A second significant update is the addition of a red-dot finder in place of the older model’s metal peep sight. Whether or not you see this as an improvement depends on how adept you were with the previous aiming device. Basic though it was, the peep sight had the notable advantages of never dewing up or requiring a battery! The Astroscan’s red-dot sight suffers from an all-toocommon ill: its light source ranges from bright to way too bright. I was able to dim the finder’s LED by dotting it with a felt marker and then wiping off most of the ink with my finger before it dried. On the plus side, this finder is one of the few I’ve seen that has a clear (nontinted) view window, which makes sighting faint stars easier. However, if you’re left-eye dominant, as I am, you will probably find yourself using your other eye to aim the scope because of the finder’s low-profile mount. Another change with the new Astroscan involves the eyepieces. The RKE-design models of yore have been replaced with Plössls. Included with the scope are 28-mm (yielding a magnification of 16×) and 15-mm (30×) eyepieces. Given that Plössls are a more advanced design that can handle the scope’s fast optics better, this is a meaningful improvement. Thankfully, the one thing that hasn’t changed is the Astroscan’s superb documentation. Beginners will benefit richly from the inclusion of The Edmund Sky Guide (by Terence Dickinson and Sam Brown), the new

Astroscan User’s Guide (by James Mullaney), and a nifty planisphere. All scopes marketed as “introductory” should be so well equipped!

Astroscanning the Night Away The Astroscan’s calling card has always been its ease of use. Simply set the base on a sturdy table, place the scope in the base, and away you go. I did my testing with the base sitting on the optional anti-skid rubber mat ($7.95), which is a useful accessory if you use the scope on a smooth surface. The setup is remarkably stable. A sharp rap to the Astroscan’s tube dies out instantly — there’s simply no vibration. Excellent. And the ball-in-socket design also ensures you can always orient the eyepiece to a convenient angle. The 28-mm eyepiece’s 3° field of view, in conjunction with the red-dot finder, makes aiming the scope a piece of cake. This is especially important for beginners, who often struggle with this task. Low-power, wide-field views are the Astroscan’s forte. I spent many enjoyable hours simply meandering among the stars, drinking in the panoramic vistas, with no particular destination in mind. Scanning the Milky Way is endlessly delightful and often breathtaking. Used this way, the Astroscan really has more in common with large binoculars than it does with conventionally mounted telescopes. As good as the Astroscan is for sweeping star fields, it proved less well suited to high-magnification work.

SPECIFICATIONS & MEASUREMENTS* Astroscan Plus Telescope Aperture

4 /1 8 inches (105 mm)

Central obstruction

1.5 inches (36%)

Focal length

17.9 inches (f/4.3)

*All values measured by Sky & Telescope.



S&T Test Report

The Astroscan is capable of providing stunning wide-field views of the Milky Way. The scope (minus dew shield) stands only 19 inches (48 centimeters) high when aimed straight up.

If detailed views of the planets are your main interest, you should probably consider other scopes first. At magnifications above 50×, the images in my test

Quick Look

Kendrick’s Stargate Observer Tent Price: $795 Canadian Kendrick Astro Instruments 36 Cawthra Ave., Toronto, Ont. Canada M6N 5B3 416-762-7946; kendrickastro.com

Summer means many things to many people, but summertime camping is a surprisingly universal activity that spans national borders and cultural divides. And if you’re an amateur astronomer, camping usually means bringing a telescope along to enjoy the sky. So why not have a tent that accommodates people and telescopes? That makes perfectly good sense to the folks at Kendrick Astro Instruments, and the Stargate Observer Tent is the latest and best-yet model in their line of tents. I had a chance to test the Stargate prototype last summer. It was identical to the current production models, except that the new version has an enlarged sleeve

makes centering objects at high power a challenge. I also found that the focuser’s motion, though generally quite good, became a bit jumpy when the scope was

for one of the support poles, making the tent’s assembly easier. Speaking of which, without instructions, I completed the first-time set up in less than 40 minutes. Then again, I’m 6 foot 4 (193 cm tall), and I’ve assembled a lot of tents over the years. The process would be very easy for two people, especially if, unlike me, they read the instructions beforehand explaining the color-coded system for identifying the proper positions for the support poles!

From experience I know that not all tents are created equal. The Stargate’s construction is, however, right up there with the best of the best. The tent’s design, materials, workmanship, and attention to detail are first class. The basic structure has a footprint about 10 feet (3 meters) wide and 14 feet long. The “observing” section has 4-foot side walls and an opening roughly 6 feet wide and 6½ feet long. As with all of Stargate’s doors, there’s a bug screen that

The Stargate Observer Tent’s “inner” structure is, by itself, sufficient for dry conditions. It stands more than 6 feet (2 meters) tall at its highest point. In addition to weatherproofing the whole tent, the heavy-duty rain fly adds a vestibule at the “living” end. It is seen here with the fly rolled back for observing.




The Astroscan now comes with a pair of Plössl eyepieces in place of the original RKEs. They are part of the Astroscan’s generous accessory package, which includes a planisphere, extra felt pads for the base, and two very informative instruction booklets.

Astroscan grew noticeably soft. Although bench testing showed the primary mirror to be of good quality, a star test revealed that it was being pinched by the mirror’s simple mounting arrangement. Add to that a small amount of miscollimation (which is not user adjustable), and it’s easy to see why the high-power views lack crispness. To be fair, over the years I’ve looked through many Astroscans, and most of them handled high magnification better than this one. In practical terms, the soft high-power view really isn’t a big deal. Perfect optics alone won’t make Astroscan a planetary observing machine, since the mount’s felt-against-plastic bearing surfaces have a modest amount of stiction, which

can be zippered into the opening as well as a zippered wind-proof covering. The observing section is partitioned by a zippered “wall” from the tent’s “living” section, which is comfortable for one person or cozy for two. Of course, there’s nothing preventing anyone from sleeping in the observing section. In fact, with the bug screen in place, it’s a great place to just fall asleep looking up at the stars. In dry climates it’s sufficient to use just the main tent. If there’s a chance of rain or dew, then the included rain fly is a must. Unlike the lightweight flies made for many camping tents, Stargate’s rain fly is a heavy-duty waterproof structure that covers the entire tent (with adequate tie-downs for windy conditions). The fly also adds a nice “vestibule” at the living end of the tent. With the fly in place and the vestibule open, the overall footprint is 11 feet wide and 25 feet long. In other words, it’s big. Indeed, when I set up the Stargate in the camping field at last year’s annual Stellafane convention in Vermont, one bemused onlooker offered afterward that he thought I was setting up a portable car port! The tent has a solid floor, which has the

advantage of keeping it waterproof. It also helps keep ground moisture out of the tent, which could condense on the walls during overnight cooling. But the solid floor means that scopes don’t rest directly on the ground. This isn’t a problem for hard surfaces or really heavy scopes. But lightweight equipment, especially camera tripods, can shift if the floor’s fabric moves while you’re walking around the equipment when the tent is set up on soft, grassy ground. The entire tent tips the scales at about 40 pounds (18 kg) when packed in its storage bag. It’s compact enough to tuck away in even the smallest car. And the Stargate just might possess a magic quality that isn’t mentioned on the Kendrick website. One of the reasons I brought the tent to Stellafane last year was to test its waterproof design. Given the annual convention’s track record, there was sure to be at least one shower or thunderstorm. But for the first time in recent memory the 2009 convention experienced three days of excellent conditions. I’m blaming it on the Stargate! ✦ — Dennis di Cicco

The Astroscan’s “mount” consists of the scope’s spherical body cradled in the cast-aluminum base shown here. Although extremely steady, the setup’s felt-against-plastic motions proved jerky for high-power viewing.

cold. This made high-magnification focusing rather difficult.

A Paradox

get go, other options have emerged in the 34 years since it first appeared. In particular, Orion’s StarBlast 4.5 Astro Telescope or SkyQuest XT4.5 are, in my opinion, better choices for newbies who want to see everything from splashy open clusters to Jupiter’s cloud belts and Saturn’s rings. Those telescopes were favorably reviewed in this magazine’s June 2003 (page 46) and April 2001 (page 59) issues, respectively. But for experienced observers, the Astroscan is a great second scope, offering a unique combination of ease-of-use, decent light-gathering power, and widefield views. Here’s hoping we’ll be singing its praises for years to come. ✦ Contributing editor Gary Seronik is an experienced telescope maker, user, and reviewer. He scans the skies from his home near Victoria, B.C., Canada and can be contacted through his website: www.garyseronik.com.

Although a wide-angle lens enhances the apparent roominess of Stargate’s observing section, the area really is spacious enough for a large telescope (the model shown is a 12-inch) and several observers.


The more I used the Astroscan, the more I became aware of its paradoxical nature. On one hand, its rich-field design yields

wide, bright views, making the scope about as user friendly as they come. Beginners in particular will cherish these aspects. On the other hand, the Astroscan is also a fairly specialized telescope that will appeal to more experienced observers seeking a bridge between binoculars and bigger scopes. In many respects, the Astroscan is more of a specialized instrument for wide-field viewing than it is a general-purpose scope. Don’t read these comments as a condemnation of the little red scope, since they’re not. The Astroscan is unsurpassed as a grab-and-go sky sweeper, and in my book, that makes it very worthwhile. Indeed, its views are not all that different from those of the 5-inch Apogee scope that Walter Scott Houston wrote about for decades in this magazine’s Deep-Sky Wonders column. Although the Astroscan has been promoted as a beginner’s telescope from the

WHAT WE LIKE: Very well designed First-class construction

WHAT WE DON’T LIKE: No floor opening for a telescope



New Product Showcase

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ORION TELESCOPES & BINOCULARS

GOTO DOBS Leave it to Orion Telescopes & Binoculars to make an excellent telescope even better. Its new Orion SkyQuest GoTo Dobsonian series adds Go To capabilities to the popular XT line of telescopes. The new SkyQuest XT8g (8-inch f/5.9, $849.95), XT10g (10-inch f/4.7, $1,099.95), and XT12g (12-inch f/4.9, $1,599.95) incorporate high-torque servo motors and optical encoders combined with a powerful GoTo controller for precision slewing and tracking of more than 42,000 celestial objects. The Dobsonian base comes with all motors, gears, and encoders pre-installed, so you’ll only need to drop in the optical tube and align on 2 stars to begin observing each night. Each SkyQuest XTg Dobsonian comes with a dual-speed 2-inch Crayford-style focuser with 1¼-inch adapter, an EZ-Finder II reflex finder, a 28-millimeter, 2-inch DeepView eyepiece, and a 12.5mm illuminated-crosshair 1¼-inch eyepiece, and a one-year limited warranty. Orion Telescopes & Binoculars, 89 Hangar Way, Watsonville, CA 95076 800-447-1001; www.oriontelescopes.com ▴

IMAGE PROCESSING TUNE-UP CCDWare updates its popular image-processing software with the release of CCDStack Version 2 ($199.95, or upgrade from an earlier version for $100). This powerful program contains all the tools you’ll need to create breathtaking deep-sky astrophotos. CCDStack Version 2 is optimized to take full advantage of multi-core processors and 64bit operating systems. The software enables you to easily calibrate and combine your CCD or DSLR images with the click of a button. It also includes easy-to-implement processes such as “live” digital development stretching (DDP), and advanced data rejection routines, such as sigma reject, that display which pixels in each image will be rejected. Its deconvolution algorithms have also been enhanced to correct for minor tracking errors. A fully functioning 30-day trial version is available to download. Requires Microsoft Windows XP, Vista, or Windows 7. CCDWare, www.ccdware.com 58 July 2010 sky & telescope


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July 2010

59

Alan MacRobert Celestial Calendar

Pluto Crosses Bright & Dark A rich Milky Way patch and a blank dark nebula form the backdrop for Pluto this year.

In losing

its planet status four years ago, faint little Pluto gained more attention than it’s had since its discovery in 1930. And more is on the way. In 2015 NASA’s New Horizons probe will examine the dwarf planet and its three known moons close up for the first time, as

New Horizons chief scientist Alan Stern described in last month’s issue, page 30. Pluto this year is in the northwest corner of low Sagittarius, and during the summer it crosses two extremes of the starry background. In June, during the dark-Moon period from about the 5th to

18h 16m

18h 15m

Barnard 93 (dark nebula) Jun 23

19th, Pluto is seen against some of the richest Milky Way fields in the sky, a star cloud so bright that it gained its own Messier number, M24. Then from about July 3rd to 8th, at the beginning of the next moonless period, Pluto drifts across a blank, starless bit 18h 14m

18h 13m

Barnard 92 (dark nebula)

27 Jul 1

5

9 13

17 21 25

Au 2

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es

PHOTO: ROBERT GENDLER

Star magnitudes

6 7 8 9 10 11 12 13 14

S A G ITT A R IU S si

er

24

Two years of Pluto’s path. Note the dark nebula it crosses early this July.



18h 20m Jan 1

18h 16m B93

Jun 1

May 1

18h 12m B92

Jul 1

Pa th of Aug 1

Jan 1

Sep 1

6603

Pluto 2009

6603

M

Pl ut o 2 0 10 Y

–18°

Pluto

es

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er

Oct 1 24

Star magnitudes 6 7 8 9 10

–19°


MSgr

MSgr

stars, no matter how faint, lie in front of it. For the remainder of July’s moonless period, from the 9th to 19th, Pluto travels through an area where stars are sparse but

of sky of the sort that William Herschel called “a hole in the heavens.” This is the opaque dark nebula Barnard 92, a dust cloud near enough that practically no

m

S AGI TTAR I US

18h 12m

18h 11m

–18° 15´

Path

ug 2

of P lut o

6 10 14

18 22 26 30

Sep 3

–18° 30´

7 11 15 19 23 27 Oct 1 5 9 13

–18° 45´

North of the Sagittarius Teapot, the small blue rectangle shows the field of the key chart above. The star Y Sagittarii appears on both. On the large chart below, Pluto’s position is marked with a tick at 0h Universal Time every four days.

not obscured completely. Then for the rest of 2010, Pluto is back in the rich Milky Way. In which surroundings will Pluto be easier to find? In the area with no other barely visible specks that could confuse the issue? Or with many faint stars to provide precise position markers? The big map here shows Pluto’s path from July through October; for May and June see SkyandTelescope.com/pluto. The maps show stars to magnitude 14.5, a little fainter than Pluto at magnitude 14.0. With Pluto’s low altitude nowadays, you’ll need at least a 10- or 12-inch scope, unless perhaps you’re in the tropics or the Southern Hemisphere, where Pluto crosses the sky much higher each night. Once you’re aimed at the right spot, and once the landmark stars closest around Pluto’s position have glimmered into view as best they will (give them time), switch to very high power to see as deep as possible. Ticks on Pluto’s path mark its position at 0:00 Universal Time every four days. Put a pencil dot on Pluto’s position for the date and time you plan to observe. It may help to make an enlarged copy of your part of the chart for use in the dark. And if your scope gives a mirror-image view (which happens if the light is reflected an odd number of times, as in most scopes that use a rightangle star diagonal at the eyepiece), then mirror-image the chart as well. As Pluto recedes farther into the outer solar system year by year, it’s becoming an ever tougher challenge. Happy hunting! ✦ — Alan MacRobert and Tony Flanders Sk yandTelescope.com July 2010 61


Now Available for Sky Gazing

2010 Skygazer’s Almanacs

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