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Journal of the Amateur Astronomers Association of New York October 2008 Volume 56 Number 10, ISSN 0146-7662

EYEPIECE
ysis of Cassini pictures. Lanes are created within the ring system and if you were to follow them around the planet you would see them spiraling inward," Porco explained. Moonlets, such as Pan, are responsible for the ring gaps. They create a ridge-like or scallop effect along the edge of the rings.
Saturn's 60 moons are divided into inner and outer groups. The inner group gets the most study. Of these, only seven are massive enough to have collapsed into a spheroid shape.

Saturn, Its Moons and Rings Are Always Fascinating
By Thomas Haeberle
In the summer of 2004, the Cassini spacecraft, in the rich complex system of Saturn, set up the farthest outpost ever established by humans. Beginning a September 15 Hayden lecture, Carolyn Porco, Director of Cassini Imaging Central Laboratory for Operations (CICLOPS), used Cassini to pay tribute to our species. She noted that humankind refused to recognize limitations, flung its machines into space and for 50 years has been exploring the cosmos. Missions like Cassini, she added, add up to "a story about us and our epic journeys through the solar system." Porco said that "Saturn and its companions offer the promise of observing processes at work similar to those responsible for the makeup of the solar system and for producing the habitable environment on our own planet."
Saturn is a dream planet, highlighted by its enormous rings that would fit nicely between Earth and the Moon. "They are made mostly of water-ice and if you were to collect the entire mass of particles together, you would get a moon equal in mass to a 300 mile-wide moon like Enceladus." The rings were probably once a moon whose orbit came too close to Saturn and was ripped apart by tidal forces. "By studying the rings, we discover the same processes at work in galaxies and other disk systems." The rings are broken down by sections, with the main rings A, B and C, "with the B ring having the most mass and most structure." Within the rings are waves of particles that are driven by Saturn's many moons and moonlets. It is assumed they're microscopic dust particles that have levitated from the ring plane of Saturn. "The density of the rings can be figured out by an anal-

"Saturn is 10 times farther from the Sun as is the Earth. The Cassini spacecraft is massive (half its weight being fuel), and needed gravity assists from the inner planets to eventually launch it out to Saturn." A fly-by on the way out took Cassini past Jupiter on the eve of the millennium year 2001.
"There were 82 passes of the moons, with 44 of them passing Titan. Some of the fly-bys came as close as the International Space Station comes to Earth." There are a diverse group of worlds such as Tethys, Dione, Rhea and Mimas, the latter known as the Death Star moon for its uncanny resemblance to the Star Wars movie's battle station. "Orbiting moons that got too close t o Sa t u r n got smashed, forming the rings. Collisions continued to pulverize the debris." Porco spoofed her own theory through a "planet wars" mini-movie showing Mimas smashing up moons with its death ray to create the rings. Iapetus is one of the most intriguing objects in the solar system with its distinctive two-tone color. There are Porco continued on page 10


What's Up
By Tony Hoffman The Sky for October 2008
Vesta Crosses the Whale. T h e con st ella t ion C et u s the Whale is best known for its stunning long-period red variable star Mira ("the Wonderful"), which every 11 months rises from obscurity to become an easy nakedeye sight. It's due to reach maximum in late December. As Cetus is situated a few degrees off the ecliptic, which runs through neighboring Pisces and Aries, it is occasionally the host of planets major and minor, particularly ones with high-inclination orbits such as Mars, Mercury and numerous asteroids. Currently, Eris, the dwarf planet whose discovery ultimately led to Pluto's demotion, lies in Cetus, where it has spent the past 80 years and will linger for the next 30 as well. This past May, far-ranging Sedna, which takes some 11,000 years to circle the Sun, crossed from Cetus into Taurus after spending 180 years in Cetus. A much nearer world zips through Cetus this month, as asteroid 4 Vesta travels from near Menkar (Alpha Ceti) to a point west of Gamma Ceti, reaching opposition on October 29. At magnitude 6.4, it should be an easy binocular target, even from the city. October's Constellations. As t h e sk y d a r k en s, Ar cturus twinkles low in the west, while the Big Dipper hugs the northwestern horizon. Cygnus soars overhead, while Vega lies just west of the Swan, and Hercules and Corona Borealis are well into their westward swing. Sagittarius, which holds both Jupiter and the center of our galaxy, is low in the southwest. From there, the Milky Way arcs up through Ophiuchus, Scutum and Aquila to Cygnus, then down through Lacerta, Cepheus, Cassiopeia and Perseus. Capricornus lies to the south, with lone Fomalhaut twinkling to its lower left. The Great Square of Pegasus climbs in the northeast, trailed by Andromeda, Triangulum and Aries, while Cetus lies low in the southeast. The Pleiades and Capella rise by 9 p.m., followed by Aldebaran. Orion joins the scene by midnight. October 1 M oon lies n ea r October 4 M oon lies n ea r October 6 M E SSE NG E R approach to Mercury. October 7 M oon lies n ea r at 5:04 a.m.
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October 14 F u ll M oon a t 4: 02 p .m . October 17 M oon a t p er igee, 226,069 m iles fr om Earth, 2:09 a.m. October 21 O r ion id m et eor sh ower p ea k s; la st -quarter Moon at 7:55 a.m. October 22 M er cu r y a t gr ea t est elon ga t ion in p r ed awn sky. October 25 M oon lies n ea r Sa t u r n . October 26 Ven u s lies n ea r An t a r es. October 27 M oon lies n ea r M er cu r y. October 28 New M oon a t 7: 14 p .m . October 29 Ast er oid 4 Vest a a t op p osit ion . October 30 M er cu r y lies n ea r Sp ica .

Bountiful Jovian Eclipses
By Joseph A. Fedrick
The lunar eclipse in volving the Moon we three years. However, been observable with a February was the last eclipse in'll see from New York in some eclipses of Jupiter's moons have telescope or perhaps binoculars.

I used a six-inch reflector August 25 to see Europa cast a tiny black shadow on the Jovian cloud tops. I observed the shadow moving across Jupiter between 8:50 and 9:10 p. m. At 9, Europa emerged from in front of Jupiter so I could see both the moon and its shadow. Jupiter's moons are hard to see when in front of the planet because their color nearly matches that of the Jovian clouds. I saw Io and its shadow cast onto Jupiter shortly after 8 p. m. on the evening of September 1. I observed Ganymede gradually disappear into Jupiter's shadow around 8:40 p. m. The moon gradually faded out into eclipse for two minutes, starting at 8:38. I watched Io gradually reappear from eclipse in Jupiter's shadow for more than one minute from 8:40 to 8:41 on the night of September 3. I used an f/9 6-inch Newtonian reflector with around 150x magnification. Although I couldn't see the shadows of Jupiter's moons on the planet with my 60 mm refractor, eclipses of the moons in Jupiter's shadow should be observable with a small refractor and even with binoculars. October should provide some good views of the eclipses because Jupiter is near quadrature. This means eclipses of the moons by

Ven u s. An t a r es. sp a ce p r ob e m a k es close J u p it er ; fir st -quarter Moon

Fedrick continued on page 10


A Message from AAA President Richard Rosenberg
Hello, members: Urban Starfest at the Central Park Sheep Meadow last month was a great success. Hundreds of people came to look through more than a dozen telescopes pointed at the Moon, Jupiter, the Andromeda Galaxy, the Ring Nebula and many other targets. Sunny Corrao of the Urban Park Rangers and her staff were terrific, as were all of you who brought your scopes. The 2008-09 AAA lecture series at the American Museum of Natural History begins at 6:15 Friday evening, October 3. Dr. Mordecai-Mark Mac Low of the museum will speak on "Puzzles of Planet Formation." The series will feature monthly lectures through May, usually on the first Friday. All lectures are free and open to the public.

Our observers' group has gotten a facelift. Using the club's laptop computer and the Cartes du Ciel planetarium program, we can illustrate upcoming sky events, and learn the movements of the planets and stars. The OG, as it 's called, will continue to meet the last Saturday of the month from 1 to 4 p. m. at our current headquarters, 1010 Park Avenue (85th Street) in Manhattan, through the end of the year. In 2009 we intend to move to a different location and possibly a new day and time. I hope to have more news on this next month.
Rich Rosenberg, AAA President, pr esident @a a a .or g, (718) 522-5014

A Glast by Any Other Name is Still a Blast
By Mary Carlson
And what a blast it's been. The Gamma-Ray Large Area Space Telescope was recently renamed the Fermi Gamma-ray Space Telescope. Enrico Fermi, a pioneer in high-energy physics, was the first to hypothesize how cosmic particles could be accelerated to high speeds, thus laying the groundwork for understanding phenomena such as gamma-ray bursts. The new scope will be discussed at the October 23 recent advances seminar. Launched into Earth orbit June 11, the 4Ѕ-ton spacecraft is an endeavor of the U. S., France, Italy, Sweden and Japan, with 18 partners. With its five-year mission and 10-year goals, it will determine the high-energy behavior of gamma-ray bursts, and their sources, those known and those yet undiscovered; understand the mechanisms of particle acceleration in active galactic nuclei (AGNs), neutron stars and the remnants of supernovas; and probe dark matter and the early universe. Its scope of exploration will include gamma-ray bursts and the gamma-ray background, blazars, AGNs, neutron stars, black holes, cosmic rays, supernova remnants, our solar system (Sun, Moon and Earth), the Milky Way, the early universe and dark matter. Fermi's two main instruments are the Large Area Telescope (LAT) and the Gamma-ray Burst Monitor (GBM). LAT operates as a particle detector rather than a conventional telescope as gamma rays can't be brought into focus with mirrors or lenses. There are 16 towers of particle detectors, each with four components. Tracker consists of a four-by-four array of modules designed to measure the paths of electrons and positrons produced from the initial gamma rays. The calorimeter measures the energy of a particle when it's totally absorbed. The anticoincidence detector is the silicon strip that fits over the tracker, distinguishing and filtering out cosmic particles from electron-positron pairs of gamma rays. The data-acquisition, the "brain" behind LAT, analyzes data to find gamma rays and determines which signals to relay to Earth. Carlson continued on page 9
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Adaptive Optics: The Truth Behind the Myths
By Edward J. Fox
"Adaptive optics will make t h is ea r t h b ou n d t elescope as powerful and as sensitive as the Hubble Space Telescope." We've all heard this claim. Dr. Pamela Gay and Fraser Cain addressed this topic in Episode 89 of their podcast show Astronomy Cast (www.astronomycast.com). Gay is a visiting assistant professor of physics at Southern Illinois University, Edwardsville. Cain is publisher of the Universe Today website (www.universetoday.com). The mirages and shimmers you see looking down the surface of a road on a hot day are similar to the distortions temperature changes and air currents cause when light from a distant source zig-zags through Earth's atmosphere. An object as small as 1/10th of an arc second (1/10th of a human hair held at arms length) may be distorted or blurred to appear to be to be a fuzzy 3 arc seconds in diameter. Astronomers have tried t o m in im ize t h is d ist or tion by going as high as possible, to mountain tops and into space. Since the 1950s they've been trying to develop adaptive optics for Earthbound telescopes. In fact, much progress in the field was achieved by the military. Gay describes the basis of adaptive optics with the example of an ocean wave approaching the shoreline, a wave that started as straight but was distorted by wind gusts, current and rocks. To have the now-curved wave strike the shore at one time, the shoreline would have to be reconfigured to match the wave. Adaptive optics tries to deform t h e m ir r or so it matches the distorted light wave, according to Gay. This reshaping is done by pistons which flex the mirror to the needed shape. The amount of flexing is determined by measuring a portion of the light, from a known source, through a grid of lenses arrayed like a chessboard and all focused at a receptor grid at a set distance. A perfect wave of light from all the lenses would focus in a perfectly centered image on each element of the receptor grid. But in reality, the distortion would cause some of the light to be focused to the left, some to the right, some high and some low. This information is fed
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by computer to the pistons to reshape the flexible mirror. Scientists measure light from a known source. A nearby bright star is used when it's close enough. In other cases, a laser beam creates a "fake star," sometimes by exciting sodium atoms high in the atmosphere. Scientists also measure the image of a known star and flex the image so it's as round as possible. Gay says the atmosphere can be thought of as a carnival mirror which distorts the image. Adaptive optics can be thought of as the inverse mirror which restores the object to its true shape. This all sounds great, b u t a s fa st a s on e cor r ect ion is made, the need for another is detected. These changes have to be made as rapidly as possible, 1,000 times a second in some cases. There are other limitations. First, these corrections are limited to very small fields of view, a few tens of arc seconds of sky. The Andromeda Galaxy or various nebulae can't be imaged, as they are by the Hubble Space Telescope. Also, adaptive optics can't be used for photometry to measure light coming from the subject stars. Fortunately, these are areas where spacebased telescopes are suitable. Adaptive optics is also best used in the infrared. So what's the best use of adaptive optics and why is it portrayed as being so good? Adaptive optics, according to Gay, is best at resolving relatively small objects, such as binary stars. At its best, adaptive optics can achieve higher resolutions from the ground than the Hubble can achieve. According to Gay, "We can achieve resolutions as low as three-tenths of an arc second or smaller, in near-perfect circumstances. We can search for exoplanets. We just cannot do the photometric analysis of a planet transiting the star." While adaptive optics is limited t o ext r em ely small fields of view, scientists are working to broaden them. One method under study is the use of multiple reference-point stars surrounding a larger field of view. Another is flexing more of the corrective mirror. Although adaptive optics may not be totally worthy of all the current hype, it certainly is powerful within its limitations and at the very least will help free space-based telescopes to do what they do best in analyzing larger fields


Review: A Stupendous History of Astronomy
By Dan Harrison
More than a month ago, I p ick ed u p T Street Journal a nd quickly hea r d my ja w dr op. reported that the Vatican is planning to erect a the Vatican gardens of--are you ready for Galileo. h e W all An r ticle statue in this?-- and Saturn? Or that Jamaican natives cowered as Columbus pointed out a lunar eclipse he predicted thanks to astronomical tables? We inevitably get to the great debate over h eliocen trism and one of the book's most interesting illustrations: Tycho Brahe's vision of the universe, "which steered a course between Ptolemy's Earth-centered cosmos and the Sun-centered cosmology of Copernicus. The Sun circles the central Earth which remains stationary; meanwhile, the other planets orbit the Sun." Predictably, the material on Tycho, Kepler, Copernicus, Galileo, Newton, Halley and others rivets the reader. Especially interesting is material on the "tantalizing hints" to Tycho in Hamlet. Was the play's burning star Tycho's brilliant supernova? "As a boy, Shakespeare... could have seen the new star of 1572, and [it]...would provide a simile for the arrival of the glowing Ghost of Hamlet's father on the battlements."

Some 375 years after the church put Galileo on trial for heresy, it "wants to close the Galileo affair and reach a definitive understanding not only of his great legacy, but also of the relationship between science and faith," said the head of the Pontifical Academy of Sciences, which will sponsor building of the statue with the aid of an anonymous donor. The news was a perfect setup t o r ea d in g a b ook t h a t I can't praise enough. From the excellence of its writing to the sweep of its illustrations--everything from historical drawings and photos of historical sites to recently observed phenomena--"The History of Astronomy (Firefly, $59.95) can solve the problem of what holiday book to get a fellow astronomy buff, or yourself. The price is well worth it. As authors Heather Couper and Nigel Henbest note, "Our ancestors built monuments that are aligned with the heavens. From Stonehenge to the great Pyramids, from the native North American structures at Chaco Canyon in New Mexico to the mysterious mounds of Bronze Age Britain, it is clear that...the sky was as important to humanity as events on the Earth." A fascinating series of objects sh ows h ow t h ose wh o passed before us were absorbed by the heavens. Examples: A 1,000-year-old petroglyph that bears an "uncanny" resemblance to a total solar eclipse; the Bronze Age Netra Sky Disc that shows the Sun, its celestial boat, the crescent Moon and the seven stars of the Pleiades; a Chinese star chart, engraved in stone, that shows 1,434 stars grouped into 283 small constellations; and a Babylonian tablet describing observations of Halley's Comet in 164 BC. Illustrations like these and superb accompanying text sweep the reader along. Did you know that the "star" of Bethlehem may have been a close approach of Jupiter

Even more intriguing, t h e a u t h or s st a t e, a r e t h e names Rosencrantz and Guildenstern. "Shakespeare probably met" two Danish noblemen with the same last names when they were envoys to London. "These gentlemen were both relatives of Tycho, and they must surely have spoken to the ever-curious playwright about Denmark's most flamboyant character."
Some even suggest that "Hamlet" is an allegory of the contest between astronomers of the time, with the wicked king Claudius representing Ptolemy's Earth-centered view of the universe--his full name was Claudius Ptolemaeus--and Hamlet acting the role of the new Suncentered astronomy of Copernicus. Historical nuggets continue apace. I n 1942, d u r in g World War II, powerful radar jamming covered all of Britain. The presumed culprit was a German secret weapon. However, analysis showed the jamming was coming from the Sun. There was an enormous sunspot group generating solar flares that spew streams of energetic electrically charged particles into the solar system. "It would be an intimation that we live in a violent universe," the authors of this terrific book observe, with
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Briefs: Possible 1st Picture of Planet Orbiting Sun-Like Star
Astronomers have taken wh a t m a y t h e fir st p ict u r e of a planet orbiting a star similar to the Sun. The world is about eight times the mass of Jupiter and lies far from its star, about 330 times the Earth-Sun distance. But for all the planet's strangeness, its star is quite like our Sun. Previously, the only photographed extrasolar planets have belonged to brown dwarfs. And while hundreds of exoplanets have been detected by noting their gravitational tug on their parent stars, it's rare to find one large enough to image directly. Further study will be needed to prove that the planet is in fact orbiting around the star. The system lies about 500 light-years from Earth. Though the star has about 85% the mass of the Sun, it's younger than our star. To image the system, the team utilized adaptive optics. The strange planet so far from its parent star is unexpected based on theories of star and planet formation. The exoplanet, at about 1,500єC, is much hotter than Jupiter, at -110єC. Astronomers have long argued wh et h er m a ssive galaxies form from scratch, or by chunking together smaller galaxies. Lately, evidence is building for the latter theory, and a new study adds to the growing picture of galaxy formation as a clumpy affair. Using groundbased and space telescopes, astronomers recently observed groups of huge galaxies merging, showing large, established galaxies can still grow bigger. Astronomers observed three meshing galaxies about 4 billion lightyears away. The new finding supports the theory that large galaxies come about in steps as smaller galaxies are pulled together by their mutual gravitational attraction. But the very most massive galaxies don't seem to be growing at as high a rate as middle-mass galaxies. And when astronomers look at the brightest galaxies now compared to the brightest galaxies at an earlier time, they don't seem to have gained much mass. Dust devils raging across Mars' arctic plains were caught on film by NASA's Phoenix Mars Lander. Phoenix captured images of at least six dust devils and sensed a dip in air pressure as one passed near the lander. The whirlwinds had been expected in Phoenix's landing site near the north pole. The dust devils range in diameter from 7-16 feet. The day the camera saw dust devils, Phoenix' recorded a sharp dip in the thin atmosphere.
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theory that the universe's most massive stars carve out these wispy wombs and thereby enable stellar embryos to take shape. Stars are born within clouds of gas and dust that dot most galaxies. Scientists think turbulence from the wind of other stars within these clouds gives rise to knots of material with enough mass that gas and dust begins to collapse under their own weight. The theory goes these stars are so hefty some of their material slides off in the form of winds. The scorching-hot stars also blaze with intense radiation. Over time, wind and radiation blast away surrounding cloud material. As winds and radiation make more room, gas and dust get pushed against the rim of the cavity. By looking at Sun-like stars in t h eir in fa n cy, r esearchers have peered at planet formation. The result is three wildly different setups suggesting our solar system is neither unique nor strange. When a star is born, there's often a leftover cloud of gas and dust that flattens into a thin disk. The material orbits the star in the direction of the star's rotation, looking something like the Saturn's rings. In that disk, knots of material form and some eventually become planets. Scientists explored such disks around three young Sun-like stars. In regions where the dust appears to have been cleared out, molecular gas is still highly abundant. This can mean the dust has clumped together to form planetary embryos or that a planet has already formed and is in the process of clearing the gas in the disk. Researchers didn't actually see planets. Instead, they used spectro-astrometric imaging, to give them a window into the inner regions of the disks where Earth-like planets may be forming. Observations offering the closest view yet of t h e heart of the Milky Way present strong evidence for a black hole. By linking a series of radio telescopes around the world, astronomers created a virtual telescope with resolving power of a single dish the size of the distance between the various sites, about 2,800 miles. The instrument grabbed an image that probed nearly to the black hole's event horizon. The presumed black hole is obscured by gas and dust, so researchers looked at radio light. Researchers observed a bright source of light, Sagittarius A*, thought to mark a black hole 4 million times the mass of the Sun. Sagittarius A*'s diameter equals Continued on page 7

A new portrait of a star-forming region su p p or t s a


Briefs: Large Hadron Collider Passes Major Tests
Continued from page 6 about one-third the distance between Earth and the Sun. This small size indicates the mass in the galactic center is denser than previous measurements found, which supports the idea that the hidden object must be a black hole. The world's largest particle collider p a ssed it s fir st major tests September 10 by firing two beams of protons in opposite directions around a 17-mile underground ring in what scientists hope is the next great step to understand the makeup of the universe. Protons traveled clockwise along the full length of the Large Hadron Collider, described as the biggest physics experiment in history. Five hours later, scientists fired a beam counterclockwise. Physicists have much greater power to smash components of atoms together in attempts to learn about their structure. Eventually two beams will be fired at the same time in opposite directions with the aim of recreating conditions a split second after the Big Bang. The collider is designed to push the proton beam close to the speed of light. Scientists hope to eventually send two beams of protons through two tubes, speeding through a vacuum colder and emptier than outer space. The paths of these beams will cross, and a few protons will collide. Experiments could reveal more about dark matter, antimatter and possibly hidden dimensions of space and time. The collider could also find evidence of the hypothetical particle believed to give mass to all other particles, and thus to matter that makes up the universe. A spectacular nearby star explosion ob ser ved in 1843 is now thought to be a previously unknown type of explosion that leaves stars intact. Eta Carinae, 7,500 light -years away within the Milky Way, brightened in 1843. Astronomers in recent decades have studied the cloud of gas and dust that billows away from the star. Astronomers have seen stars like Eta Carinae get brighter, but not as bright as a real supernova. It's a mystery what can brighten a star that much without destroying it completely. The 1843 event may have been an explosion that produced a fast blast wave similar to but less energetic than a supernova. Rather than a surface eruption, as suspected, a true explosion may have occurred deep inside the star. A study of small galaxies cir clin g t h e M ilk y W a y found that while they range dramatically in brightness, they pack about the same mass. This suggests there's a minimum size for galaxies. Spinning around the Milky Way are at least 23 pint-sized galaxies, each shining with the light of anywhere from 1,000 to 1 billion Suns. The finding could help explain dark matter and how it affects galaxy formation. Despite their wide-ranging brightnesses, the galaxies seem to have a central mass of 10 million times the Sun's. Almost all that mass seems to be dark matter, with just a tiny smidgen of visible matter producing stars. Though they qualify as galaxies, the satellites aren't pinwheel spirals like the Milky Way and its cousins. They look more like diffuse, puffy balls of light. There may be no dark matter clumps smaller than these galaxies, and their size represents critical mass necessary for dark matter to condense into a clump. Martian valleys were carved over lon g p er iod s b y recurring floods when Mars might have had wet and dry seasons, a new study suggests. This contradicts suggestions that large valley networks were the result of shortlived catastrophic flooding, lasting just hundreds to a few thousand years and perhaps triggered by asteroid impacts. The thinking supposes that asteroid impacts, as fuel for floods, would have created features not found on Mars. Rainfall may have been seasonal, or wet intervals may have occurred over longer cycles. But conditions that allowed for of liquid water on the surface must have lasted at least 10,000 years. Changes from dry to wet periods might have had to do with periods of greenhouse -gas outgassing associated with volcanic eruptions, large impacts or a change in the tilt of Mars' rotation. A fork-like probe on the Phoenix M a r s L a n d er h a s sensed changes in humidity in the air, but finds the dirt below dry. Measurements indicate water vapor is settling on or in Martian dirt, then being released back into the air daily. The lander has already confirmed the presence of a subsurface layer of water ice, first detected in 2002. Phoenix is searching for clues this layer was once liquid. Scientists think water vapor detected in the Martian air should be present as a thin layer of moisture on the ground. Discovery of a water ice layer and the apparent transition directly into the gas phase of ice samples gathContinued on page 8
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Briefs: Two Astronomers Get MacArthur `Genius' Awards
Continued from page 7 ered by Phoenix indicate moisture should be collecting on surface dirt. A huge comet-like object h a s b een sp ot t ed in sid e Neptune's orbit. The object, at least 30 miles wide, is on the return leg of a 22,500-year journey around the Sun. It's just over 2 billion miles from Earth, though its elongated trek takes it to 150 billion miles. Though basically a comet, it never gets close enough to the Sun to develop a long, bright tail of evaporated gas and dust. The orbit could have formed in the belt of icy debris beyond Neptune, then kicked to a large distance by a gravitational encounter with Neptune or Uranus. But it's believed more probable it's from the Oort Cloud's inner edge. Astronomers have glimpsed the largest clu st er of galaxies ever seen in the distant, early universe. Discovery of this group offers further proof of the existence of dark energy. The light started about 7.7 billion years ago. A team discovered the cluster by chance while surveying a portion of sky for a catalogue of X-ray sources. They spotted an extremely bright object without any galaxy visible in optical light nearby and determined the source of the light was a far-off group of galaxies containing the mass of about 1,000 Milky Ways. Since dark energy contributes to stretching of the universe, and speeds the process of galaxies receding from each other, it has hampered growth of massive galaxy clusters. Scientists have discovered h igh -energy gamma rays near the Crab Nebula pulsar that oscillate in alignment with the star's spin. The finding may shed light on the intense environment deep inside the Crab. Scientists are trying to understand magnetic fields around the pulsar and emission mechanisms making the pulsars pulse. The gamma rays they found are being produced by a cloud of high-speed particles circling the pulsar. The gamma rays are polarized, meaning their electric fields move up and down in one direction, in the same direction as the axis of the pulsar's spin. This tells scientists the light is produced close to the pulsar. The discovery is yielding insights into the processes involved in making a dead star so active. Learning more about the Crab system helps scientists unravel the complicated workings of pulsars. The Crab, 6,500 light-years from Earth in Taurus, is the
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brightest pulsar around. Cassini has found two new partial rings a r ou n d Saturn that each accompany a small moon, shedding light on what determines whether a partial or complete ring forms with the moon. The partial rings, ring arcs, extend ahead of and behind the small Saturnian moons Anthe and Methone in their orbits. Anthe and Methone orbit Saturn where gravity of the nearby larger moon Mimas disturbs their orbits. Mimas provides a regular gravitational tug on each moon, which causes them to skip forward and backward in an arc-shaped region. A violent merger between two ga la xy clu st er s a p pears to have split ordinary matter from dark matter. Hubble and Chandra show dark matter from each cluster appearing to pass through the cosmic mess unscathed, leaving ordinary matter behind. Hubble helped map the distribution of dark matter in the collision by seeing light bending around areas with dark matter. Chandra spotted X-rays from hot gas that makes up the bulk of ordinary matter in the clusters. The new separation suggests darkmatter particles interact only weakly outside gravity's influence, given that they passed one another inside the collision zone with little visible effect. Each cluster is almost 1 quadrillion times the mass of the Sun. The collision was 5.7 billion light-years away. At presstime, Johns Hopkins/Sp a ce T elescop e Science Institute astronomer Adam Riess and UCLA astronomer Andrea Ghez received "genius grants" from The John D. and Catherine T. MacArthur Foundation, which awards recipients in diverse fields $500,000 fellowships, over a five-year period, to use as they wish. Riess was honored for studies into the geometry of the universe. He and colleagues have shown not only that the universe is expanding, but the rate of expansion is accelerating. He's also led efforts to use the Hubble to increase the precision of the data, and is designing experiments and devices to detect and measure dark energy. Ghez is pioneering ways to minimize image distortion caused by the Earth's atmosphere. She initially used a technique called speckle imaging, in which very short exposures are digitally added to increase resolution. More recently, she's been using adaptive optics. Among other findings, she's used the technique to identify a supermassive black hole at the center of the Milky Way.


Events on the Horizon October 2008
M: members; P: open to the public; T: bring your telescopes, binoculars, etc.; C: cancelled if cloudy; HQ: at AAA headquarters, 1010 Park Avenue (between 84th and 85th streets); AMNH: For ticket information, call (212) 769-5200 For directions to AAA observing events, check the club's website at www.aaa.org. Observing at Great Kills Gateway National Park, Staten Island, P, T, C Next date: November 1 Wednesday, October 8, 8-11 p. m. Observing at Prospect Park, Brooklyn, P, T, C Next date: November 5 Monday, October 20, 7:30 p. m. Hayden Planetarium lecture, P, AMNH Author and scientist Jeffrey Bennett will present a whirlwind tour of the search for life in the universe: Tuesday, October 21, dusk-10 p. m. Observing at Cadman Plaza, Brooklyn, P, T, C Thursday, October 23, 6-8:30 p. m. Recent Advances in Astronomy seminar, M NYU, 239 Greene St., Room 801. Saturday, October 25, 10 a. m.-noon Solar Observing, P, C Conservatory Waters, Central Park. Next date: November 22 Saturday, October 25, 1-4 p. m. Observers' Group, M, HQ Next date: November 22 hours. What once took previous missions up to a year to accomplish, Fermi will perform in days. Scientists anticipate not only the vast acquisition of knowledge, but also the challenge of new perplexing mysteries. At the seminar, we'll not only discuss discoveries from Fermi, but updates from MESSENGER as it swings past Mercury, surprising new findings from Cassini and final reports from the Phoenix Lander as it shuts down for the Martian winter. See above listing for details.

Friday, October 3, 6:15 p. m. AAA lecture, P Mordecai-Mark Mac Low, chair of the astrophysics department at the AMNH, opens the AAA's 2008-09 lecture series when he speaks on "The Mysteries of Planet Formation" in the Kaufmann Theater of the museum. Friday, October 3, 8-10 p. m. Observing at Floyd Bennett Field, Brooklyn, P, T, C Next date: November 7

Friday, October 3, 6-7:15 p. m. Sunset nature walk followed by stargazing, Robert F. Wagner Park, Battery Park City, Manhattan, P, T
Friday, October 3 and Saturday, October 4 Custer Institute and Observatory Annual Astronomy Jamboree, P Friday, 6-midnight at the institute, Saturday 9:30-6:30, Southold High School. Speakers include author Dava Sobel and Vatican research astronomer Brother Guy Consolmagno. Info: CusterDonna@yahoo.com. Saturday, October 4, dusk Carlson continued from page 3 The GBM, as the complementary in st r u m en t , con sists of 12 detectors to catch X-rays and lower-energy gamma rays and two detectors for higher-energy gamma rays. This should greatly enhance the study of the actual mechanism of gamma-ray production. The LAT will see one-fifth of the sky at any given moment and scan to map the entire sky every three

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Porco continued from page 1 sharp divides between dark and white areas and it's believed dark material has been scooped up, possibly from the dark moon Phoebe. Porco showed images of sunward -facing craters with dark ridges exposed in prolonged sunlight. Thermal heating--exposing, darkening and evaporating icy material on one side and precipitating or snowing on the other "seems to explain the mystery," Porco observed. The dark side also has a n eq u a t or meters high in some places, giving shape. In Arthur C. Clarke's "2001: A Porco noted, it was Iapetus where an super-advanced alien civilization took as depicted in the movie. ia l r id ge 20 k iloIapetus a walnut Space Odyssey," encounter with a place, not Jupiter

These are the solar system's only large bodies of surface liquid known to exist, other than Earth. Cassini images found evidence of liquid water reservoirs that erupt in geysers on Enceladus. The surface is geologically young although relatively smooth. There are impact craters and evidence of tectonic activity. Porco's final image of Saturn was from behind the planet, illuminated by the Sun, giving meaning to the title of her lecture. The Earth is seen through its rings, a small pale dot. These and other images can be found on the Cassini website: http://ciclops.org. Fedrick continued from page 2 Jupiter's shadow aren't hidden behind Jupiter as they are around the opposition of Jupiter.

The high point moment of the mission was the releasing of the Huygens probe, which landed on Titan on January 14, 2005. "Huygens landed in an area m oist wit h h yd r oca r bons, a mud flat. It looks Mars-like with ice cobbles." Drainage patterns were seen during its descent but no liquid bodies found until Cassini flew closer over the polar regions. Radar images captured large liquid hydrocarbon lakes and their coastlines, with numerous islands.

Contacting the AAA
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