Документ взят из кэша поисковой машины. Адрес оригинального документа : http://www.aaa.org/EyepieceFiles/aaa/2009_06_June_Eyepiece.pdf Дата изменения: Sun Feb 22 20:31:03 2015 Дата индексирования: Sun Apr 10 03:37:04 2016 Кодировка: Поисковые слова: р п р п р п р п р п р п р п р п р п

EYEPIECE
Journal of the Amateur Astronomers Association of New York June 2009 Volume 57, Number 6, ISSN 0146-7662

How `Stuff ' Provides Clues to Origin of Solar System
By Terrell Kent Holmes
I study stuff," Denton Ebel said proudly. "Stuff is what I'm interested in." Ebel, associate curator and associate professor of earth and planetary sciences at the AMNH, def ined "stuff " and its signif icance in the May 1 AAA lecture, "Stardust Findings and Meteorites: New Constraints on Solar System Formation Models". He discussed how some of this stuff f igures in the origins of the solar system, and described anomalies that make tracing those origins problematic. Stardust was the f irst space mission to return samples of extraterrestrial solid material since the Apollo era. Before this, information about chondrites, meteorites and such was provided through gathering of interplanetary dust particles captured by silicon plates applied to the wings of high-flying aircraft. Stardust, launched in 2001, captured ions from the solar wind, one component of Ebel's beloved stuff. The data were sent to Earth via a canister supported by a parachute. The parachute didn't open up, though, and the craft crash landed in Utah. What was salvageable was taken to UCLA and analyzed via an instrument known as a "Mega SIMS," SIMS standing for Secondar y Ion Mass Spectrometer. The sample was bombarded with cesium atoms. Secondary ions of oxygen arose from this bombardment, then accelerated and were sent into a spectrometer, where they were analyzed. "One of the most important elements in the solar system, of course, is oxygen," Ebel said. There are three stable isotopes of oxygen--O16, O17 and O18. "The actual amount of oxygen in a thing can be characterized by the total amount of O16. And then we look at the ratios of O17 to O16, and O18 to O16. So we're not looking at the abundance of oxygen in a rock, but we're looking at the isotope ratios in a rock. When we look at rocks that we know come from Mars, they're not quite on the same line. They have a different composition and ratio of isotopes. And that's the easiest way for us to identify Mars rocks, to look at their oxygen isotopes. When we look at rocks we think come from Vesta, they're not on the same line as Earth's either, so these bodies, which were homogenized at one time, had separate ratios of O16, O17 and O18 relative to each other when they formed." Ebel discussed the components of chondrites and their role in determining planetary formation. "We look at these chondrites in vivisection and see chondrules, little blobs of stuff that were molten in space and collected together to make the rocks we call chondrites. When I take the oxygenisotope composition using a laser instrument, I look at different grains [and] f ind I get points near the end of the same data f ield I would get in O17 and O18 space for the whole chondrule. That's consistent with what I see. But if I look at some of these grains in the center of the chondrule, I f ind they go way down [in the f ield of data]. That's not consistent with chemistry that happens on Earth. There's a signature there of some other stuff, and we don't know what that is, and we want to know what it is. " Material captured by Stardust from the solar wind was off the beaten path of the line where terrestrial-related chondrites lay. "So we're all anomalous," Ebel said. "We don't belong in the solar system. We have oxygen-isotope compositions that are not the same as the bulk of the solar system, which is the Sun, by def inition." Ebel thought this was fascinating. "These little pieces that are leftovers of the most primitive stuff somehow capture the same oxygen isotopecomposition that the Sun has, yet that's not what's seen in Mars, Vesta, the Moon and the meteorites we have access to in bulk." A c c o rd i n g t o E b e l , t h e m a i n i d e a c o m i n g f r o m Stardust data is that stuff formed by the hot Sun that was then ejected or thrown by solar wind out to the Kuiper Belt. Other proposals include shocks. "In the [Milky Way] galaxy we have these spiral arms that are formed by gravitation. These can create shock waves if they're in a disc the size of our solar system. There's also the shock that happens when things are accreted to the solar system. These discs form from large cloud cores in planet-forming regions and starStuff continued on page 2


What's Up
By Tony Hoffman
The Sky for June 2009
June's Constellations. The nights around the Summer Solstice are brief, but f illed with some of the most splendid nights of our sky. We see our own galaxy at its best, with the galactic center, the Sagittarius, Ophiuchus, and Scorpius region, at its highest in the south in the early evening. From there the summer Milky Way stretches up across the eastern sky through Scutum and Aquil, to Cygnus, then down into the northeast through Cepheus to Cassiopeia. The area around the galactic center is rich with star clusters (open and globular) and nebulae, but they're also found elsewhere in the summer sky, such as the globular clusters M13 and M92 in Hercules, which is high in the east, and M3 in Canes Venatici. Lyra, with its brilliant star Vega, stands high in the east, above Cygnus, while equally bright Arcturus, in Bootes, stands near the zenith. Meanwhile, the Big Dipper tilts towards the northwest, and Virgo stands in the southwest. Cancer with Jupiter sinks westward, trailed by Leo, while Castor and Pollux stand side-by-side above the twilight, preparing to depart. A small world with an identity crisis comes to opposition in northern Sagittarius this month, though 14th-magnitude Pluto may be hard to identify in this star-rich region of the sky. Jupiter blazes in Capricornus at magnitude -2.6, rising shortly after midnight. June 5 Venus at greatest elongation from Sun in morning sky. June 6 Moon occults Antares. June 7 Full Moon at 2:12 p.m. June 13 Mercury at greatest elongation from Sun in morning sky; Moon lies near Jupiter. June 15 Last-quarter Moon at 6:15 p.m. June 19 Moon lies near Venus and Mars in morning sky. June 20 Moon lies near Pleiades in morning sky. June 21 Summer Solstice is at 1:46 a.m.; Moon lies near Mercury. June 22 New Moon at 3:35 p.m.; Mercury lies near Aldebaran. June 23 Pluto at opposition; Moon at perigee. June 26 Moon lies near Regulus. June 27 Moon lies near Saturn. June 29 First-quarter Moon at 7:28 a.m. g

April Flowers Bring May Showers
By Joseph A. Fedrick
A dry late winter season and early spring provided clear skies for viewing after the February and March meetings of the Observers' Group, but by late April the sky became cloudy so that Mercury and Saturn were obscured by clouds and the crescent Moon was only intermittently visible between the clouds on April 28, the night of the April meeting. Rain followed during early May so I couldn't get a good view of Saturn until May 10. Even then, the sky was partly cloudy. Saturn appeared as a markedly oblate, almost eggshaped, paletan-yellow disk with faint brownish cloud belts in my 6-inch Newtonianreflector at 150x. The rings were tilted at about 4 degrees, the maximum tilt for this year. They appeared dull and brownish as comparedto the brilliant white when they were tilted near their maximum in earlier years. The inner crepe ring wasn't readily visible and the outer B ring was barely perceptible. The Cassini division between the darker outer A ring and inner brighter B was perhaps at the threshold of visibility. The ring shadow on Saturn's disk was visible crossing near theequator, and the north and south equatorial belts were visible onSaturn's disk on either side of the rings. The preceding edges of the rings were darker and browner than the following edges on the other side of the planet, which were slightly bluish and a bit brighter. The A and B rings, and Cassini division, were less diff icult to discern. Saturn appeared nearly as spectacular in Michael O'Gara's 76-mmapochromatic refractor at 120x on March 31 even with a smaller aperture (3 inches vs. 6 inches). The apochromatic refractor had the advantage of producing sharp contrasting images due to the lack of a central obstruction and lack of chromatic aberration. g Stuff continued from page 2 forming regions. There's an accretion shock when stuff comes in [at high speeds] and slams into the disc. So maybe everything's getting homogenized and heated and condensed way out there," he said, gesturing to the boundary beyond the solar system. "That's why we need a global disc model. We need to have a model for modeling this disc the same way they do global climate models that predict climate over long periods of time." Stardust is now on its way to Comet Tempel I to gather more data. "That's why these missions are so important, because they provide the constraints, things we have to answer." But for now, Ebel and others will just have to settle for providing the age-old answer: We're not sure. g

2


A Message from AAA President Richard Rosenberg
Hello members: I thank the members of the club for re-electing me to the board of directors and to the board for re-electing me as president. More details on the annual meeting can be found in Dan Harrison's article below. The AAA will have deep-sky observing sessions at North-South Lake in the Catskills this summer. We'll be limited to four cars at each session. The location, about 125 miles from the city, is exceptionally dark. It is about a two-and-a-half-hour trip each way from the city. Besides the campground and other nearby places to lodge, there is a possibility of staying at a member's summer place nearby. We'll have a list of observing dates shortly. Irv Robbins, director of the observatory at the College of Staten Island and a former board member of the AAA, is looking for amateurs to help discover asteroids. The college now controls robot observatories in Arizona and Australia and may get involved with Hawaii. I'm not sure if the work will involve making images, looking at images or both Volunteers will be trained. The Brooklyn Bridge Park Conservancy, which hosted the free "Movies with a View" last summer, is having a money-raising event on Thursday, June 4. Four Dobsonian telescopes will be available. We need one more person to operate the fourth. Free refreshments will be available (and we don't have to pay admission).

Rosenberg Re-elected AAA President for Fourth Term
By Dan Harrison
Richard Rosenberg was elected to a fourth one-year term as AAA president by the AAA board of directors following the May 20 annual meeting. Other off icers were re-elected: vice president Rik Davis, treasurer Thomas Haeberle, f inancial secretary Alice Barner, recording secretary Edward J. Fox and corresponding secretary Ron McCullough. At the annual meeting, members re-elected four members to three-year terms on the board of directors: Rosenberg, McCullough, Eyepiece editor Dan Harrison, and Amateur Astronomers Medal recipient and Eyepiece columnist Tony Hoffman. Two new members were elected, Joe Delfausse and Jocelyn Wilkes. John Delaney and Richard Tihany didn't stand for re-election. Outlining the state of the club, Rosenberg said the big news of the past year was the move of the AAA to its new headquarters at 120 Warren Street in downtown Manhattan. This provides better visual capability and Internet connection. "We can make use of planetarium programs regarding what's up and coming up." In addition, the seminar on recent advances in astronomy met at New York University, though in the summer it will move to headquarters. "We've saved considerable money on rent while at the same time upgrading our presentations. With Internet access and computer software, our seminar has available up-to-date news on space missions, scientif ic discoveries and new comets. At the Observers Group we can illustrate upcoming celestial events with a planetarium program." The club plans an online version of Eyepiece shortly, he continued. "This will enable the club to save considerable expense in postage and printing costs, and effort in monthly mailings. In return, those receiving Eyepiece online will be able to receive not only the articles but images and star charts." The club continues to expand its observing sites. It's arranged for dark-sky observing at North-South Lake in the Catskills. "Thanks to the efforts of Jason Kendall," Rosenberg noted, "we're back in Inwood Hill Park with multiple observing sessions each month. We've begun astronomy talks followed by observing at the Salt Marsh Nature Center in south Brooklyn." Rosenberg noted that the club has established a relationship with the Brooklyn Bridge Park Conservancy. AAA members staffed telescopes at the park's "Movies with a View" series last summer and will do so again this year. The scopes will be out again at a Conservancy money-raiser on Thursday, June 4 at Pier 5 in Brooklyn Heights. "We hope to develop similar relationships with the Audubon Society at Prospect Park and the Intrepid Museum." Rosenberg continued on page 4

3


Galileo's Telescope in Philadelphia and on PBS Show
By Luis Marcelo Cabrera
Last month I visited "Galileo, the Medici, and the Age of Astronomy" at the Franklin Institute in Philadelphia. The exhibition, which runs through Sept. 7, is actually two exhibitions. The f irst part, "Medici Collection," starts with armillary spheres, astrolabes and similar instruments, followed by maps and codexes. There are numerous examples of compasses, dividers, quadrants, nocturnals (instruments used to determine the time based on the position of a star, like a sun dial), and perspective and surveying instruments, both civilian and military. The show also discusses science in the age of Galileo. The second part of the exhibition is called "Galileo's Telescope" and features one of the two known surviving telescopes that Galileo used during his lifetime. The 400-year-old telescope was Galileo's observing telescope rather than his more ornate presentation telescope. Also featured are drawings of the Moon by Galileo with annotations, charts of Jupiter's moons with measurements of position relative to time and manuscripts with possible explanations for Saturn's rings. There are abundant hands-on sections with telescopes, lenses and lasers demonstrating how the different types of telescopes work, and their strengths and weaknesses. Interactive video screens highlight the signif icant discoveries of Galileo's time and their impact on science. At the end of the exhibit there's a short introduction to the problem of determining longitude at sea and Galileo's Jovilabe. The Jovilabe was meant to determine longitude by f inding the time, using the positions of Jupiter's moons. Not discussed in the exhibition, but mentioned as you exit the show, is the issue of church and science, and Galileo's trial. The exhibition has free audioguides through the use of a cell phone. At the end of my visit I checked out other activities related to the International Year of Astronomy and was pleasantly surprised by the Fels Planetarium show "Two Small Pieces of Glass," which tells the story of two teenagers going to a local star party, and their discoveries and learning about telescopes and their history. This brings me to the PBS documentary "400 Years of the Telescope, A Journey of Science, Technology and Thought," an hour-long show recently broadcast. The f ilm featured several prominent scientists and scientif ic historians, including Hayden Planetarium director Neil de Grasse Tyson as narrator and such historical f igures as Galileo and Newton. The show covered advances in astronomy since Galileo f irst used a telescope to look at the sky 400 years ago. The creation and science behind telescopes were explained in detail, as well as the differences between refractors and reflectors, their history, mechanical diff iculties encountered in manufacturing them and their associated discoveries. There was also emphasis on advances since the Hubble Space Telescope started to operate, and the importance of having a f ixed-up and upgraded Hubble or some other more advanced instrument looking at the sky. The superb illustrations and animations in the documentary helped explain, in very simple language, concepts somewhat diff icult to understand when presented for the f irst time, such as expansion of the universe, adaptive optics and interferometers. The show overall was very entertaining and captivating, but also very educational and almost guaranteed to inspire future astronomers. A companion book to the show has been published, by well-known astronomy writer Donald Goldsmith. It's "400 Years of the Telescope: A Journey of Science, Technology and Thought." g Rosenberg continued from page 3 Work has proceeded slowly on development of the club's class, Rosenberg said, but in June, "we'll present the f irst part of a PowerPoint presentation dealing with our understanding of the solar system from prehistoric man to the space age. This will be free to all members." Rosenberg also pointed to the success of the club's lecture series, including standing-room-only for talks by Robert Nemiroff of Astronomy Picture of the Day, and AAA member and Hayden Planetarium director Neil de Grasse Tyson, who spoke on Pluto. At the annual meeting last year, Tyson created a $3,000 matching fund to benef it the club and honor Fred Hess. Contributions from members quickly achieved the fund's target. "As the f irst fruit," Rosenberg noted, "we've bought a CCD imager which, when inserted into a telescope in place of an eyepiece, converts incoming photons into images that can be seen on a computer monitor. This is a terrif ic educational tool. Many people can see images at once. Hard-to-recognize objects such as lunar craters or moons of Jupiter can be pointed out." The club has ordered a dozen Galileoscopes, simple scopes similar to, but easier to use, than the one Galileo used. These should arrive in June and will be featured at observing sessions, Rosenberg said. He noted that he's sent letters in support of light-pollution legislation to the governor and key legislators in Albany, and urged members to do the same. g

4


Balloon-Borne Scope Delves into Early Universe
Several years ago, a team of scientists hoping to f igure out how the galaxies formed launched a revolutionary new telescope under a NASA high-altitude balloon to unlock the evolution of the universe. The BLAST (Balloon-borne LargeAperture Sub-millimeter Telescope) mission, which staged long-duration flights over Sweden in 2005 and Antarctica in 2006, is the subject of a documentary, "BLAST!" being shown in New York this month. Filmmaker Paul Devlin followed the story of his brother, Mark, a University of Pennsylvania professor of astronomy and astrophysics, and the project's principal investigator. Mark Devlin was in charge of a collaboration that designed the telescope. Flying the telescope above much of the atmosphere allowed the BLAST team to peer into the distant universe at wavelengths nearly unattainable from the ground. The study has uncovered dust-enshrouded galaxies that hide about half the cosmic starlight. In the 1980s and 1990s, certain galaxies called ultraluminous infrared galaxies were found to be forming hundreds of times more stars than our own local galaxies. These starburst galaxies, 7 billion-10 billion light-years away, were thought to make up the far infrared background discovered by the COBE satellite. The BLAST study combined telescope survey measurements at wavelengths below 1 millimeter with Spitzer data at much shorter infrared wavelengths. Results conf irm that all the far infrared background comes from individual distant galaxies, solving a question of the radiation's origin. Thus, as much as half the universe's light energy is infrared from young, forming galaxies. BLAST's extragalactic survey, at wavelengths of 0.25, 0.35 and 0.5 millimeters, provided new limits on the abundance and brightness of starburst galaxies for both the low- and highredshift universe. The instrument has a 2-meter primary mirror along with a camera made of hundreds of bolometers, sensitive detectors cooled to 0.3 degrees above absolute zero. With three wavelength bands operating, BLAST determined the spectrum of submillimeter light coming from distant galaxies. This measurement gave the temperature of each galaxy and, ultimately, its estimated rate of star formation. In one 11-day balloon flight, BLAST found more than 10 times the total number of submillimeter starburst galaxies detected in a decade of ground-based observations. The study documented a large population of cold clouds of gas and dust, many cooled to less than -260 C, which form the birthplace of stars. The New 11 at the IFC one showing Village, 12th June 12-18. York premiere of "BLAST!" is Thursday, June Center, 6th Avenue and 3rd Street. There will be on that day. The f ilm then moves to Cinema Street east of 5th Avenue, for f ive shows a day

Images, photographs, sky maps and the complete study are available at http://www.blastexperiment.info/. If yiou want further information on the f ilm, proceed to info@blastthemovie.com. g

Astronomical League Slates August Convention in NY
The Astronomical League convention comes to our area August 8 and 9 at Hofstra University, Hempstead, N. Y. It's cosponsored by the AmateurObservers' Society of New York, and Hofstra's physics and astronomy department. The program will include guest speakers with expertise in such areas as astrophysics, exobiology, astronomy hardware, observing techniques, astronomy art, astronomy history and radio astronomy. The many speakers include David Levy, "A Night Watchman's Journey: My Life and Hard Times as a Comet Hunter"; NASA Goddard's Nancy Kiang, "Astronomical Detection of Life on Other Worlds: Biosignatures of Photosynthesis"; author Phil Harrington, "Nights of Future Passed," which reviews the amateur telescope over the 20th century; Al Nagler, president and founder of Tele Vue Optics; Tony Pirera, founder and president of Spectrum Thin Films, where coatings have been deposited on f ilters for NASA space probes, such as the Mars Phoenix Lander; astronomy writer/educator Joe Rao, "Great Comets of the Last 400 Years"; and Dr. Michael Inglis of Suffolk County Community College, on detection of extremely high-energy rays. Other session topics include "Dark Skies as a Universal Resource," "Night-Sky Network Materials for Astronomy Education," "Recent Developments on20Jupiter," "Amateur Imaging of Mercury" and "Variable Star Observing." The convention will also feature astronomy vendors. Pre-convention activities starting August 2 include tours of the Hayden Planetarium and Brookhaven National Laboratories. Early convention registration, at a discount, is open until July 1. Info: www.alcon2009.org. g

5


The Continuing Saga of the Twin Martian Rovers
By Dan Harrison
Addressing the Explorers Club May 2, Cornell astronomy professor Dr. Steven Squyres noted that the twin Martian rovers Spirit and Opportunity were in day 1,895 of their 90-day mission. Squyres, lead scientist for the Mars Exploration Rover Project, had no way of knowing that just four days later, on May 6, Spirit would get stuck in sandy soil and would be delayed in its voyage towards Goddard Crater, 250 meters south of its location when he spoke and a possible volcanicexplosion crater. But Squyres' outline of the rovers' achievements in what's been the greatest overland trek of a planet--they were designed to go 600 meters--was hardly diminished by that news. After all, the rovers have sustained several glitches and have continued their duties. In his talk to the Explorers Club, Squyres noted that there have been previous stalls in the Martian sand. Vehicles on Earth have simulated the predicaments by being partially put in sand, clay and earth. This was even used to guide scientists in extracting a robot from a sand dune. "The optimal technique," Squyres observed, is to do what many earthlings do: "put it into reverse and gun it." Outlining highlights from the rovers' f ive years on Mars, Squyres noted that Spirit found a dry riverbed flowing into Gusev Crater. "We wanted to f ind sedimentary rocks but found igneous rocks. We still think sedimentary rocks are down there but are covered by lava." When Spirit climbed Husband Hill, it saw layering materials that could only have formed by the action of water, Squyres said. "About 1,200 days into the mission, soil popped up like snow. It was 91% pure silicone, evidence of a hot-spring deposit. " A key to the rovers' longevity has been the Martian winds. At one point, Squyres recalled, dust led to decreased power. "We thought Spirit was close to the end, but we hit the windy season so lower power was less of a problem because the rover's solar ar rays had been cleaned off by the wind." Opportunity's landing site was chosen by chemistry. "Hematite is a chemical that serves as a beacon since water may have been present," Squyres said. "Layered bedrock is right near the impact crater. The layering is f ine grain, and we found hematite right away. We found rocks made of hematite and evidence that water soaked the ground. Ripples that transported rocks were evidence of water. So water blew across the surface and headed across the countryside." Opportunity is heading for Endeavor Crater after having visited the Eagle, Victoria and Endurance craters. Endeavor is much older than Victoria and Endurance, so it may provide a look at bedrock. The rover, having spent two years exploring Victoria, has adduced evidence that not only did water shape much of the crater's region, but that liquid water could have formed in well-below-freezing temperatures if there were enough minerals in it. Meanwhile, getting Spirit unstuck was proving diff icult at press time. On the science end, the exact makeup of the dirt the rover is stuck in isn't known. Spirit is sampling its surroundings to provide clues. On the mechanical end, Spirit's right front wheel has been dead for three years. That makes it harder to use the f ive remaining wheels to pull the rover out." In his remarks to the Explorers Club, Squyres said that Spirit and Opportunity have lasted so long due to "very good hardware, overengineering and luck due to windy gusts that boost power by cleaning the vehicles, especially Spirit. The next rover, slated for launch in 2011, will have a different payload that will be able to detect organic molecules if they are there. The rover will be powered by nuclear, not solar. That means "we don't need solar ar rays and don't need wind gusts to clean the craft." Asked how long he thought the rovers might continue, Squyres, as if ready for the question, replied, "My wife keeps asking me that." g

AAA Officers for 2009-10
President - Richard Rosenberg Vice President - Rik Davis Treasurer - Thomas Haeberle Financial Secretary - Alice Barner Recording Secretary - Edward Fox Corresponding Secretary - Ron McCullough

6


Review: The Intense Scientific Disputes about Europa
By Katherine Avakian
"Unmasking Europa: The Search for Life on Jupiter's Ocean Moon" (Copernicus Books, $27.50) by Richard Greenberg, is a richly detailed book stating the author's strong belief that this is largely an oceanic world with a thin and permeable shell of ice, presenting an environment for possible life. Greenberg, professor of planetary science at the University of Arizona, was on the imaging team for the Galileo mission, which arrived at the Jupiter system in 1995. The spaceship was crash landed into Jupiter in 2004 to avoid contaminating Europa. The book is replete with images from that mission and by Voyager 2 as it flew past Jupiter in 1979. Another segment of the imaging team, viewed by Greenberg as the "establishment," came up with a different view of Europa, one in which ice tens of kilometers thick blankets and isolates the ocean below. How this viewpoint dominated despite Greenberg's evidence is spelled out. It's not a pretty picture. Indeed, of a prior book on Europa geared to the academic science community, he says, "Some individuals beholden to the U. S. planetary exploration establishment really hated it....They didn't like what I had to say about how science is done in the context of a major big-ticket space mission...." Greenberg's presentation of the scientif ic makeup of Europa is believable. It's about the size of our Moon. Its close proximity to Jupiter, with some 300 times the mass of Earth, generates great tides on Europa. This tidal action produces heat which keeps most of its water liquid. The tidal action also stresses the moon, causing its surface to crack, creating systems of ridges as water from below rushes up. Over long periods of time, the cracks open and close each Europan day (3 1/2 Earth days), pushing up newly-formed ice each day to build these ridges which overlay older ones. "Tracking the ridges gives us a way to unravel the history of the cracking of Europa's crust. From the paths that the ridges take over the surface, we can read the history of the stress of tides." Greenberg describes other areas of "thermal disruption," such as Conamara Chaos, "where the crust briefly melted, allowing blocks of surface ice to float to slightly displaced locations before refreezing...." These areas of chaos replace an earlier surface with a "lumpy, bumpy matrix with somewhat displaced rafts." Europa's few large impact craters show evidence pointing to a thin ice covering, Greenberg states. Craters such as Tyre and Callanish "record impact penetration to liquid water, which resulted in temporary exposure of the ocean to the surface. Blocks of crust were broken apart and dislodged, then locked into place as the exposed water refroze." He notes the presence of the same type of lumpy matrix and broken rafts that characterize areas of chaos. The only difference in their formation is an impact from above in one case and heating from below in the other. On the other hand, proponents of a thick-ice theory believe that convection within the ice and cryovolcanism could produce areas of chaos as well as other small upwellings. Greenberg admits convection is "possible in an ice crust, but only if the ice meets certain criteria," such as fluidity involving temperature and size of ice-crystal grains. The ice crust also needs to be thick enough for vertical motion to take place. He concludes convection is "plausible, although by no means a certainty or even a likelihood." Greenberg also points out why cryovolcanism is improbable on Europa. Since liquid water is denser than ice, it would remain below unless there were "pressure chambers to force the liquid upward." In any event, "the watery magma could not come from the global ocean. The ocean could not be pressurized enough to reach the surface...." "It seems bizarre that political clout would be used to promote a scientif ically weak position," but that's what happened. Those who didn't get on the thick-ice bandwagon paid a price. Although Greenberg was a member of the Galileo imaging team, he always felt marginalized. He wasn't among those planning the image sequences, or making the initial interpretation of the images. "The surprise was how quickly it gelled into a party line, requiring adherence to the thick-ice paradigm." The book's scientif ic information, accompanied by astounding imagery, is detailed and believable. The political story of the Galileo mission is told fully. Greenberg doesn't hold back. Throughout, there's the feeling that he just needs to get the anger and frustration off his chest. It's an enlightening and dispiriting story. He says, "There is no evidence that the ice on Europa is convecting, nor is there any other evidence that it is thicker than 10 km. It is time to get off the bandwagon." g

How to Contact the AAA
If you want to join, volunteer your time, participate in events, have a question or need to change your address, email secretary@aaa.org, or leave a message at AAA hq: (212) 535-2922. Also, visit us on the web at www.aaa.org. If you're interested in writing an article for Eyepiece, contact editor Dan Harrison at editor@aaa.org.

7


Briefs: Most Distant Object in Known Universe Detected
A stellar explosion has smashed the record for most distant object in the known universe. The gamma-ray burst came from about 13 billion light-years away when the universe was 630 million years old. It easily sur passed the most distant galaxies and quasars, showing scientists can use these spectacular events to pinpoint the f irst generation of stars and galaxies. The burst most likely arose from explosion of a massive star. What's seen is probably the demise of a star, and probably the birth of a black hole, in one of the universe's earliest stellar generations. NASA's Swift satellite f irst detected the 10-second-long burst April 23, and quickly pointed its ultraviolet/optical and X-ray telescopes. It found a fading X-ray afterglow but no visible light. That suggests a very distant object because the universe's expansion eventually stretches all visible light into longer infrared wavelengths. The infrared light of the afterglow had the highest redshift ever measured, meaning the wavelengths were very stretched out during their long journey. Atlantis astronauts bid farewell to the Hubble Space Telescope May 19 and released it back into orbit after the last-ever service call on the observatory. They did f ive spacewalks. All of Hubble's instrument bays are now full for the f irst time since 1993, when astronauts removed one to install corrective mir rors to f ix the observatory's blurry vision during its f irst service call. In its f inal tune-up May 18, astronauts added batteries, insulation and a guidance sensor. The mission added upgrades and made repairs aimed at extending Hubble's mission life to at least 2014. The 11-day mission was NASA's f ifth and f inal service call on the Hubble before the agency retires the shuttles next year. Earlier, the astronauts installed a camera for deepspace viewing, a super-sensitive spectrograph to study the composition of the universe and resuscitated two other instruments, Hubble's advanced camera and an older spectrograph. The maintenance has added batteries, gyroscopes and a science-data computer. Astronauts also added a docking ring so a robotic spacecraft can latch onto Hubble years from now and send it into the Pacif ic when its science mission ends. Atlantis also car ried an IMAX 3D camera to document the servicing mission for a documentary slated for release next spring. Hubble had been able to see galaxies and other objects that formed 700 million years after the birth of the universe, but this mission pushed that back to 500 million years. Former astronaut and retired Marine Corps major general Charles F. Bolden, Jr. has been nominated as NASA administrator. Bolden 62, would be the f irst AfricanAmerican to head the agency on a permanent basis. He's a veteran of six space flights, including being pilot on the flight that sent Hubble into orbit in 1990. The European Space Agency May 14 launched two space telescopes, Herschel and Planck, in tandem. They will peer deeper into space and time than any telescope in history. Herschel will be the largest, most powerful infrared telescope ever launched, and its observations in far-infrared to sub-millimeter wavelengths will let astronomers study some of the coldest objects in space, not visible in other wavelengths. Herschel will look for water signatures in comets in our solar system, as well as in the interstellar gas and dust clouds that give rise to stars and planets. When Herschel peers into those clouds, it will also look into the womb of star formation and should be able to see formation of proto-stars for the f irst time. The telescope will also get the f irst good glimpse at intense star formation early in the universe in young galaxies that shine brightly in the infrared. Planck will look in the microwave part of the spectrum, mapping the fossil light of the universe, the Cosmic Microwave Background (CMB), and learning more about the infant universe. Planck will look at fluctuations in the CMB in more detail than before, which will tell astronomers more about how the large-scale structures of the universe, from galaxies to large voids, formed and evolved. Planck will also turn its eye on dark matter and dark energy. The scopes' f irst observations will come in October. Herschel and Planck are slated for 3.5-year and 15-month missions, respectively. Hundreds of massive black holes left over from the early universe may wander the Milky Way, according to new calculations. They're thought to have originally lurked at the centers of tiny, low-mass galaxies. Over billions of years, the dwarf galaxies collided to form full-sized galaxies. Hundreds of the black holes should be left over, and might be shrouded by small star clusters. The closest rogue black hole is likely thousands of light-years from Ear th. Whenever two young galaxies with central black holes collided, their black holes have merged to form one black hole. But in the chaos, the black hole could be flung toward the galaxy's edges. Hundreds of such black holes could still be in the outer reaches of the Milky Way, each containing the mass of 1,000 to 100,000 suns. One sign could mark a rogue black hole: a surrounding cluster of stars yanked from the dwarf galaxy when the black hole escaped. Only stars closest to the black hole would be tugged along, so the cluster would be very compact. The renowned "pillars of creation" might have started from gaseous clumps pushed into shadowed areas by radiation from nearby stars. Such clumps creep toward darker regions of gas and dust and create dense knots, Astronomy Briefs continued on page 9

8


Briefs: Four Galaxy Clusters Collide in Major Pileup
Astronomy Briefs continued from page 8 according to new simulations. The shadows around the knots then screen out intense ultraviolet radiation that might interfere with further gas formation. The research might help astronomers better understand the pillars and similar gas environments that act as stellar wombs. Photo-ionization or photo-evaporation occurs when intense radiation from stars energizes neutral gas clouds to create a hot outer layer of ionized gas. The hot gas then expands rapidly and sends shockwaves outward into any nearby clumps. The process could explain how the pillars piled up in the images of the Eagle Nebula, about 7,000 light-years away. Perhaps the most surprising result from the new simulations: The largest clumps don't necessarily serve as foundations for the pillar-like structures. In the real universe, the Eagle Nebula's pillars may have already been knocked down by a giant supernova explosion. But the pillars will appear intact to Earth observers for 1,000 years and perhaps permit further study, because the light we see now left the scene long ago. At least one in every 100 white dwarfs may be orbited by asteroids and rocky planets, new Spitzer observations suggest. The f inding could mean these now-dead stars once hosted solar systems similar to ours. The work could also help scientists determine whether other rocky, Earth-like planets orbit other stars. As many as 5 million white dwarfs in the Milky Way could have orbiting asteroids. Because white dwarfs descend from main-sequence stars like the Sun, at least 1%-3% of main-sequence stars could have terrestrial planets. An interstellar pileup involving four galaxy clusters has become the most crowded cluster collision ever detected. Astronomers spotted the clusters involved in a triple merger 5.4 billion light-years away, the f irst time such a phenomenon has been recorded. The cosmic collision is taking place in MA0ACSJ0717, a 13 million-light-year-long stream of galaxies, gas and dark matter known as a f ilament. It continues to pour galaxies and other matter into a region already full of galaxies. MACSJ0717 is also remarkable because of its temperature. Since each collision releases energy in the form of heat, it has one of the highest temperatures seen in such a system. Astronomers have discovered an unexpected cache of spiral galaxies that apparently formed recently, long after early in the universe, when most galaxies were thought created. The younger galaxies are big and bright. The reigning hypothesis holds that such well-established spirals would have formed about 13 billion years ago, shortly after the Big Bang. But the discovery of 15 spirals that appear much younger may upset that thinking. Though just as luminous and large as normal spirals, these galaxies appear to have hallmarks of youth. They don't have nearly as many heavy elements as expected for older galaxies. Their chemical abundances suggest they're only 3 billion-4 billion years old. If this proves correct, the galaxies could present an unprecedented opportunity to study massive spirals at a younger point in their evolution, and at closer range, than generally possible. Another possible explanation for the unusual galaxies is they're the product of collisions between two smaller galaxies. This could explain why they have low levels of metals, since dwarf galaxies tend to have few heavy elements. Also, a collision can stimulate a burst of star formation, which might explain why the galaxies appear so bright. However, this scenario would require the galaxies' luminosity to multiply by about 30 times after merging, a boost much greater than usually seen. New observations of cosmic storms have found they can produce electrical cur rents g reater than 100,000 amperes (a 60-watt light bulb draws about half an ampere). The tornadoes then channel this current of flowing electric charge along twisted magnetic f ield lines into Earth's ionosphere to spark auroras. The intense currents don't pose any threat to humans, but on the ground they can damage manmade communication devices, such as power transformers. Better understanding of this is needed to improve spacestorm forecasting and to predict what might happen to power grids. The next period of maximum solar activity, due around 2012, could bring a level of storminess not seen in many decades. A recent National Academy of Sciences report said a major storm during the next peak could cripple power grids and other communications systems. "Dark gulping" is a new hypothesis about how giant black holes might have formed from collapsing dark matter, says a new computer model. In this scenario, a large cloud of dark matter could interact with gas to form a dense central mass. Depending on how the dark matter stores heat, this mass could be unstable. A small disturbance might prompt the dark matter to collapse quickly, gulping itself down to create a black hole. Though it would originally be invisible, soon it would gobble down regular matter and gas and, with all that material swirling in and being superheated and luminous, become visible. This hypothesis seems plausible, but there's no proof it ever happened. Black holes can't be seen because once light and matter get inside one, they're trapped. But on the way in, all the material creates a chaotic mess of radiation that escapes into space. From observations of far-away quasars--bright objects thought to be anchored by black holes and surrounded by intense star formation--scientists think supermassive black holes existed when the universe was less than 1 billion years old. Yet most Astronomy Briefs continued on page 10

9


Briefs: Space Junk Is Increasing Threat to Spacecraft
Astronomy Briefs continued from page 9 theories can't explain how they formed so early. Many experts have suggested supermassive black holes are the result of smaller black holes merging. But that process would likely have taken too long to account for their appearance when the universe was so young. Dark gulping is appealing because it would happen very quickly. Black holes born this way would simply be born huge, and wouldn't have to accrete the matter slowly over time. Studies attempting to f igure out what dark matter is made of and how it's spread around the universe could help prove or disprove dark gulping. The space around Earth is becoming more cluttered daily with orbital junk that, if left unchecked, will pose an increasing threat to cur rent and future spacecraft, experts told a Cong ressional subcommittee last month. While debris levels rose after the Feb. 10 collision between U. S. and Russian satellites, more rigorous tracking and cleaner spacecraft could help avoid future smashups, panelists said. The Defense Department's Space Surveillance Network, which relies on a global network of monitoring stations, is tracking more than 19,000 objects in Earth orbit larger than four inches, but there are an estimated 300,000 objects bigger than a half inch circling Earth. Most man-made junk stems from fragmentation events, in which old and malfunctioning spacecraft break apart or explode. If funding comes through for a planned Space Fence, which would use new sensors to f ill in network gaps, it could boost objects tracked in space to nearly 100,000. Attaching government space-debris sensors on commercial satellites is another possible countermeasure. NASA has found the risk of catastrophic damage from space debris around Hubble to be about 1 in 221, within acceptable limits. The agency positioned Atlantis in an orientation providing extra protection for astronauts during the Hubble repair mission's f ive spacewalks. New observations from NASA's MESSENGER spacecraft reveal 30% of Mercury never been seen up close before. A giant impact crater and evidence of ancient volcanoe equivalent to the distance between Washington, D.C., and Boston. New observations reveal Mercury's crust was largely created through volcanism, with volcanoes spitting out lava that spread and dried on the surface. The giant crater, more than 430 miles in diameter, was likely formed 3.9 billion years ago by a space rock. It's managed to survive with parts of its original floor still intact without being f illed in by later flows of volcanic lava. This is the f irst time scientists have seen ter rain exposed on the floor of an impact basin on Mercury that's preserved from when it formed. The crater floor reveals stages of volcanic and tectonic activity. The latest flyby uncovered new chemicals in Mercury's atmosphere, including magnesium. The spacecraft also measured a much more dynamic magnetic f ield around Mercury than seen during the f irst flyby. These changes are tied to powerful radiation streaming off the Sun which drives variability in Mercury's atmosphere. MESSENGER will make its third and f inal flyby of Mercury this fall before setting into orbit. Cassini has snapped a new set of photographs of Saturn from 846,000 miles out. A year into its f irst extended mission, Cassini has spent a few months beaming the most detailed images of Saturn, its moons and the outer solar system ever seen. Composites of images taken through a wide-angle lens with blue, green and red f ilters depict Saturn's rings and surface in natural color. The rings cast parallel shadows on the surface that bisect the hemispheres, captured in the latest colored image. The C and B rings dominate the foreground as gently curved and striated bands of cream and earth tones. Below, Saturn's horizon darkens, fading from a ghostly yellow shimmer to the black of space. The photos were shot from 621,000 miles. Another image reveals the sunlit planet suspended amid a segment of its rings. The rings are backlit and arch gracefully into space. They were brightened to enhance visibility. These color-f iltered images were captured from 538,000 miles. The probe will next train its cameras on star clusters to aid in calibration, then study Saturn's poles and larger rocky components of its rings. NASA's Kepler spacecraft last month began its search for other Earth-like worlds. Kepler, launched March 6, is designed to f ind planets as small as Earth that orbit Sun-like stars at distances where temperatures are right for possible lakes and oceans. It will spendmore than three years staring at more than 100,000 stars for telltale signs of planets passing in front of them. A couple of years back, scientists predicted the next peak in solar activity would be among the strongest in modern times. Now they say it could be the weakest since 1928. However, Earth-threatening solar storms could still kick up at any time, researchers cautioned. The latest forecast sees a mild peak in Solar Cycle 24 about May 2013. In 2007, scientists had predicted a peak for late 2011 or mid-2012. The Sun has been very quiet lately. This unusually long, deep lull in sunspots forced the revision. The panel predicts Solar Cycle 24 will peak in May 2013 with 90 sunspots per day on average. This would be the weakest cycle since 16, which peaked at 78 daily sunspots in 1928. g Serious valleys were carved by Martian rivers within

9


Events on the Horizon June 2009
M: members; P: open to the public; T: bring your telescopes, binoculars, etc.; C: cancelled if cloudy; HQ: at AAA headquarters, Downtown Community Center, 120 Warren St. AMNH: For ticket information call (212) 769-5200. For directions to AAA observing events, check the club's website at www.aaa.org Tuesday, June 2, 6:30 p. m., P, AMNH AAA member Jason Kendall will be the voice of the Hayden Planetarium show "Digital Universe, Tuesdays in the Dome." The "grand tour" is a 3-D overview of the universe from the smallest scales to the largest. It features the most current data sets from the largest astronomical surveys. Wednesdays June 3, 10, 24, and Saturdays June 6, 13, 20, 27, 8:30-10:30 p. m. Observing at Inwood Hill Park, Manhattan, P, T, C Next dates: Wednesdays and Saturdays in July. Wednesday, June 10, 8-11 p. m. Observing at Prospect Park, Brooklyn, P, T, C Next date: July 29. Friday, June 12, 8 to 10 p. m. Observing at Floyd Bennett Field, Brooklyn, P, T, C On the model airplane flying f ield. Next date: Sept. 11. Monday, June 15, 7:30 p. m. Hayden Planetarium lecture, P, AMNH Evalyn Gates of the University of Chicago will discuss "Einstein's Telescope: The Hunt for Dark Matter and Dark Energy." The speaker will reveal how Einstein's theory of general relativity is enabling scientists to magnify distant galaxies into view, map out the f ilaments of dark matter that wind throughout the universe and trace the influence of dark energy on the expanding and evolving cosmos. Wednesday, June 17, 8:30 to 10:30 p. m. Observing at Fort Tryon Park near The Cloisters, Manhattan, P, T, C Next date: July 15. Thursday, June 18, 6 to 8:30 p. m. Recent Advances in Astronomy Seminar, M, HQ NOTE CHANGE OF LOCATION. Next date: July 9. Tuesday, June 23, dusk to 10 p. m. Observing at Cadman Plaza, Brooklyn, P, T, C Next date: July 21. Friday, June 26, dusk to 10 p. m. Observing at Carl Schurz Park, Manhattan, P, T, C Next date: July 31. Saturday, June 27, 10 a. m . to noon Solar Observing, Central Park, P, T, C At the Conservatory Waters. Next date: July 25. Saturday, June 27, dusk Observing at Great Kills Gateway National Park, Staten Island, P, T, C Next date: July 25. Tuesday, June 30, 7 to 9 p. m. Observers' Group, M, HQ Upcoming celestial events, astronomy resources on the Internet, using telescopes and binoculars. Observing afterwards, weather permitting. Next date: July 28. NOTE: The AAA is planning observing at NorthSouth Lake in the Catskills in the months ahead. The f irst tentative date is June 20. Check aaa.org for conf irmed details.

Light Bills Move Ahead
A multifaceted light-pollution bill last month was approved by the State Assembly's Environmental Conservation Committee and sent to the Ways and Means Committee. The bill's main provision restricts installation of new lighting by state agencies or public corporation operating in the state to fully shielded luminaires. Various exemptions to the requirement are contained in the bill (A7281, S2714). One of several so-called mini bills has passed the Assembly. This bill (A5769. S4992) provides the authority for the Department of Health to "engage in and support research on the health effects of artif icial night light." It's been assigned to the State Senate's Health Committee. Three other mini bills have been approved by Assembly committees. g

11


Custer Institute Unveils Big Scope
The Custer Institute in Southold, N. Y., last month unveiled a new telescope that will be in service in its domed observatory. It's the biggest telescope in use by a public observatory on Long Island. The scope has revolutionary new optics designed and manufactured by members of Custer's observatory staff. The scope, nicknamed the Dobasaurus, is housed in Custer's third-floor, 22-foot dome. Last fall, the 25-inch, f/5 (125" 3175mm focal length) Obsession, a Newtonian-style reflecting telescope with a Dobsonian mount, was delivered to Custer from its former home at Suffolk County Community College. The scope is nearly 11 feet tall. It's also the only Dob in the area that's risen to such heights. Because of their size and the need for tall ladders to view through their eyepieces, such telescopes usually remain on the ground. But because of this scope's radical new optics, the eyepiece has been brought down to standing level. The staff has worked hard on both the optics and on retrof itting the scope with automated tracking and a variety ofother advanced features g

Traveling This Summer? This Book May Help
"Guidebook for the Scientif ic Traveler: Visiting Astronomy and SpaceExploration Sites Across America" (Rutgers University Press, $21.95) is an impressive compilation that may be of interest whether you plan tohit the road this summer or not. As a history buff, I was impressed that author Duane S. Nickell's f irst chapter is on native-American astronomy. As but one example, the Pawnee "drew star charts, built shrines dedicated to certain stars, and used the appearances of stars as a calendar." The book moves on to chapters covering optical telescopes; radio telescopes; planetaria; NASA and space exploration; space museums; astronomers, astronauts and Einstein; aliens?; space rocks, and top 10 out-of-this-world experiences. A state-by-state list of sites is provided, although page numbers for easy reference would have been useful. I also had decidedly mixed feelings about the chapter on aliens, but bow to popular interest in the subject, even though I have no plans to go to Roswell. --Dan Harrison

Amateur Astronomers Association Gracie Station P.O. Box 383 New York, NY 10028

Forwarding and Address Correction Requested

First Class