Документ взят из кэша поисковой машины. Адрес оригинального документа : http://www.aaa.org/EyepieceFiles/aaa/2009_03_March_Eyepiece.pdf Дата изменения: Sun Feb 22 20:31:04 2015 Дата индексирования: Sun Apr 10 03:39:42 2016 Кодировка: Поисковые слова: обвмадеойс нефептощи рпфплпч

EYEPIECE
Journal of the Amateur Astronomers Association of New York March 2009 Volume 57, Number 3, ISSN 0146-7662

Want First-Rate Imaging on a Snowy Day? Read On
By Edward J. Fox
It was a snowy-rainy, miserable day in New York, certainly not a day conducive to observing. But I was able to have a custom observing/imaging session that morning from my home computer. For the past month, I've been experimenting with a relatively new service: renting time on research-level telescopes online. This was brand new for me, since I've never done any astrophotography. For some time there have been services, such as Slooh, which publish their schedules for observing various celestial objects, allowing you to "snap" some low-quality images. Newer services are different in that you rent time on the telescopes and can have sole use of the telescope/observatory at that time. You can choose any object visible during your time from the scope and do imaging of a very advanced nature, including using a variety of exposure times and f ilters. The scopes are of f irst quality, being systems that might cost up to the $20,000-$30,000 range. I've experimented with two services, Global-Rent-AScope (GRAS) and Light Buckets (LB). These sites are very similar in many respects. Both offer a range of scopes in New Mexico and Australia. At present, GRAS uses 12 scopes, divided between New Mexico and Australia. LB has four scopes in New Mexico and one in Australia. The locations, on opposite sides of the Pacif ic, are conducive to extending possible observing times throughout most of any day. And the scopes in Australia obviously open Southern Hemisphere skies to residents of the Northern Hemisphere. Both systems operate on the basis of points, prepurchased for your account. In both cases, points are valued at about $1 each. Each service has a variation in the cost of the scopes' use on a time basis--so many points per minute. Think in terms of about $1 per minute. Generally, the more expensive the scope, the more costly it is in number of points per minute. GRAS has a minimum purchase of 100 points or $100 at a time. It includes a cost adjustment for phases of the Moon. The brighter it is in the night sky, the less the cost of using the scopes and vice versa. GRAS applies the cost only to the time the scope is actually imaging, not to the setup time. Light Bucket lets you pick color or black and white and the f inal quality of your image on a scale of 1 to 10. You're informed in advance as to the number of points (time) you'll use. Both sites offer free time as an inducement to new users. As an example, my session on that snowy morning cost six points, about $6. That session was a single "one-click" shot. I chose M51 from a list of deep-sky objects which were visible from that scope at that time. The scope went into a pre-set "script" for that session using the preset Right Ascension (RA) and Declination (Dec). First, the scope was slewed to f ind the object, then went through automatic routines to focus and to f ind a suitable guide star for the guidance/tracking system, including producing a preliminary image for analysis. When everything was set within its parameters, it started a single f ive-minute imaging session, tracking the target throughout that time. Unfortunately, you don't get to see any "live" image. You have to wait for the process to be completed to view the "preview image." It's automatically prepared and downloaded as a preview image in JPEG format. The preview image can be viewed online by refreshing the "last image taken" for that scope. The session's high-quality image or multiple images, depending on the number of exposures and the variety of f ilter exposures, are downloaded as zipped image f ile(s) in Flexible Imaging continued on page 8

If you haven't renewed your membership, this is your last issue of Eyepiece!


W

HAT'S

UP
Pollux, the brightest of Gemini's "twins," and Epsilon Tauri in the Hyades are the most prominent winter stars known to have planets.

By Tony Hoffman
The Sky for March 2009
Exoplanets Everywhere. As the sky darkens, Orion has crossed the meridian, while Sirius blazes due south to the Hunter's lower left. Gemini stands above Orion at the meridian. Gemini's brightest star, Pollux, was found in 2006 to have a planet two to three times the mass of Jupiter. (As with all exoplanets, this world is far too faint to be directly observed, although amateurs have helped in the detection and even discovery of extrasolar planets by indirect means, such as transits and gravitational lensing.) Another naked-eye planet-bearing star is in Taurus, in the west to Orion's upper right. Epsilon Tauri lies in the Hyades, directly across the V from Aldebaran. Its planet is very large, more than 7.5 Jupiters in mass. A 6th-magnitude star in Cancer known as 55 Cancri, visible in binoculars, has the most known exoplanets, with f ive. My favorite "exosun," though, is HD 69830, another 6th-magnitude star, which lies in a star-poor region halfway between Sirius and Alphard. It's known to have three relatively small (Neptune-sized) worlds, plus an asteroid belt about 20 times the density of our own. I've made a f inder chart available at www.flickr.com/photos/tonyhoffman/3258925459/. Messier Marathon Time. If it's March, and the Moon is near new, numerous amateurs take part in a yearly ritual called the Messier Marathon. It's so named because this month all but one of the deep-sky objects in Charles Messier's catalog are (theoretically) visible over the course of a night. The list r uns from the Andromeda and Triangulum galaxies in the early evening through the glittering open clusters of the winter Milky Way--and of course, the Orion Nebula--to the Virgo cluster of galaxies in the midnight sky to the star clusters and nebulae that surround

our galactic center in the hours before dawn. This year, the best times to try this astronomical splurge are at the very beginning of the month, when the Moon is a thin waxing crescent, and at New Moon around the 26th. March 2 Mercury lies 0.6 degrees from Mars. March 4 First-quarter Moon at 2:45 a.m. March 7 Moon at perigee; Moon lies near Pollux. March 8 Daylight Savings Time--move clocks forward one hour; Saturn at opposition in southeastern Leo. March 11 Full Moon at 10:37 p.m. March 17 Moon lies near Antares. March 18 Last-quarter Moon at 1:49 p.m. March 20 Vernal equinox at 6:45 a.m. March 22 Moon lies near Jupiter. March 26 New Moon at 12:07 a.m. March 27 Venus at inferior conjunction. g

Venus Overtakes Uranus; Saturnian Rings Near Edge-On
By Joseph A. Fedrick
I used my 10x50 binoculars to observe Venus as it overtook Uranus on January 21 and 22. Venus got to within 1 1/2 degrees north of Uranus on January 22 and easily f it with Uranus into the same f ield of view of the binoculars. Uranus, of course, was much dimmer than what I viewed of dazzling Venus. I used my 60 mm refractor scope at 50x and 100x to observe Uranus January 21. Pale-green-blue Uranus looked barely nonstellar although it didn't show such a crisp disk as it has in my 6-inch reflector at greater resolution. Venus was a dazzling off white and the disk was much larger at approximately 26" of arc vs. Uranus at 3.6"of arc. Saturn began to rise in late evening by late January and early February. The ring system appeared more like a thin line of dim brownish light extending from either side of the planet as seen in my 60 mm refractor at 50x and 100x. The appearance was somewhat like that of a whole note in music that appears above or below the staff. In fact, the ring system has never completely disappeared from sight during this apparition as it did for several weeks during the ring-plane crossing in 1980. The rings were tilted during December and January at about 1 degree and the tilt will increase this spring. Actual ringplane crossing occurs this year when Saturn is hidden in the solar glare near conjunction with the Sun. g

2


A Message from AAA President Richard Rosenberg
Hello members: Our featured event this month is the annual John Marshall Memorial Lecture at the American Museum of Natural History, honoring a former president and executive director who did much for our club. This year we're honored to have as our speaker the director of the Hayden Planetarium, former president of the Planetary Society, and AAA member Neil de Grasse Tyson to speak on "The Rise and Fall of Pluto--Witness to Demotion." Neil's latest book, "The Pluto Files," has just been released (see page 5). Mark March 13 on your calendar, at 6:15 p. m. Also note that the last two lectures in our 2008-09 series will be on April 3 and May 1, with Rick Fienberg, former editor-in-chief of Sky & Telescope, and Denton Ebel of the AMNH. See story below for details. Last year, to honor the late Fred Hess, Neil set up a fund for the club, which was quickly matched by our membership. At its meeting last month, the board of directors agreed that part of the fund would be spent on an electronic eyepiece. This is a chargecoupled device which catches photons far more efficiently that our eyes do, and displays the image on a monitor in real time. This enables many people to look at the image simultaneously. An experienced astronomer can point out features such as planetary satellites, craters of the Moon or double stars to the public. It should be quite an attention-getter. Each of our observing sites will take advantage of the eyepiece, which only costs a few hundred dollars. We're still waiting for some of you to renew your membership. If you haven't renewed, please reply now so we can avoid the expense and effort of mailing renewal letters out. Membership is still only $25. As a member you can receive a one-year subscription to Sky & Telescope for only $32.95, and/or one- or two-year subscriptions to Astronomy magazine for $34 and $60, respectively. Send your check to the Amateur Astronomers Association, Box 383, Gracie Station, New York, NY 10028. Thank you.

Tyson to Discuss Pluto in March 13 AAA Lecture
Hayden Planetarium director Dr. Neil de Grasse Tyson will discuss "The Rise and Fall of Pluto--Witness to Demotion" in an AAA lecture Friday, March 13. The free public lecture begins at 6:15 p. m. in the Kaufmann Theater of the American Museum of Natural History. Tyson's lecture is the club's John Marshall Memorial Lecture. Marshall served the AAA for many years, including as president and executive director, and is considered a key f igure in the club's growth. He died in 1997. "In this fully illustrated talk," Tyson says, "I will discuss the good, the bad and the ugly of Pluto's identity. The presentation will include a discussion of planet def initions, astronomical-classif ication schemes, the extensive history of Planet X, the discovery of Pluto and the decade-bydecade challenges to its planetary status, including the discovery of the Kuiper Belt. The talk will culminate with the back story of the Rose Center's presentation of Pluto as a Kuiper Belt object in 2000, and the 2006 vote by the International Astronomical Union [IAU] to demote Pluto. "Illustrations will include samples of candid letters and other correspondence during this time with school children, teachers, the press and colleagues on Pluto's status." Tyson is the author of the recently published "The Pluto Files," a whimsical look at the controversy surrounding Pluto's demotion from planetary status. The f inal two lectures in the AAA's 2008-09 series are: April 3: Rich Fienberg, Phillips Academy, "The More Things Change," and May 1, Denton Ebel, AMNH, "The Stardust and Genesis Sample Return Missions." g

Brit Beat Galileo On Key Observation
Galileo Galilei is often credited with being the f irst person to look through a telescope and make drawings of the celestial objects he observed. While he indeed was a pioneer in this realm, he wasn't the f irst. Englishman Thomas Harriot made the f irst drawing of the Moon after looking through a telescope several months before Galileo, in July 1609. Historian Allan Chapman of the University of Oxford detailed that 400-year-old breakthrough in astronomy in last month's edition of Astronomy and Geophysics, a journal of the Royal Astronomical Society, space.com reported. Chapman explains how Harriot preceded Galileo and went on to make other maps of the Moon's surface that Brit continued on page 9

3


A Long Wait for a Refractor, But Well Worth It
By George Hripcsak
On December 27, 1999, I put my name on the wait list for an Astro-Physics f ive-inch refractor. It arrived safely on October 20, 2008. Astro-Physics refractors are highly sought after for their excellent optics and f ine construction, resulting in the nine-year wait. I now have what's formally known as the 130mm f6.3 Starf ire EDF Gran Turismo. It's an apochromatic refractor, meaning that it focuses light of three wavelengths at the same point or, more practically, that images appear free of the false color that normally afflicts refractors. The cost is $5,675. The refractor weighs 15 pounds, but unscrews into three pieces, allowing it to be stored in a carry-on bag. At 15 pounds, plus the weight of the mount, it's not so portable. My f irst challenge was mounting it. I'm still deciding which mount to purchase, but for now I borrowed a friend's Takahashi EM200. It weighs a ton but holds the telescope securely. I plan to purchase a German equatorial mount for it. My f irst nighttime peek through the telescope was at Venus, which was quite sharp. The view revealed one benef it of a good refractor: high contrast. It takes a good telescope to tell a difference in contrast between eyepieces. I've heard of the benef its of simple eyepiece designs, which supposedly scatter less light and offer better contrast than more complex designs, but I've never seen the difference in my Newtonian telescopes. The Newtonians' mirror and secondary holder must scatter enough light to mask the difference in eyepieces. In the new refractor, my 7mm HD University Optics orthoscopic eyepiece (four glass elements) could clearly be seen to scatter less light around Venus than my 9mm Televue Nagler (seven glass elements). Similarly, while looking at Saturn another night, I found I could spot its moon Dione noticeably more easily in the 7mm HD orthoscopic than in a 7mm Televue Nagler. Dione was at the limit of its visibility. It's not that dim but was close to the planet. In addition, I could easily see Titan and Tethys on one side and Rhea on the other. Iapetus should have been visible, but was further away and was probably mistaken for a background star. I couldn't see Enceladus, which was fairly dim and also close to the planet. Nor could I see Mimas and Hyperion, which were very dim. I discovered another benef it of refractors: cold-weather observing. I brought out my 10-inch Newtonian in ninedegree weather. I was warm, but the telescope rebelled: Velcro adhesive froze and released, and struts stuck and loosened. I spent much of the evening putting it back together. The next weekend, at 16 degrees, the metal-andglass refractor did much better, with a quick cool down, stability in the wind and a pretty view of Saturn's rings almost edge on. In the last couple of weeks, I have looked at a number of objects: Comet Lulin, Eskimo Nebula (NGC 2392), Praesepe (M44), Orion Nebula (M42), Andromeda Galaxy (M31), Dumbbell Nebula (M27), Pleiades (M45), Double Cluster (NGC 869 and 884), M35, M36, M37, M38, M46, M47, M50, M66, M103, double stars epsilon Lyrae, Alberio and Rigel, and Venus, Saturn and Jupiter. For planets, the view through the f ive-inch refractor wasn't too different from that in the 10-inch Newtonian. For deep-sky objects, the f ive-inch was noticeably dimmer, as expected. I built a solar f ilter for it out of Baader Solar Film, but there isn't much to see on the Sun now that it's near sunspot minimum. I look forward to seeing a more active Sun in it. The telescope is well-built. Its two-speed Feathertouch focuser allows precise focus adjustment. The scope is full of internal light baffles to reduce scattered light. The dew shield can be locked into place when extended. The only issue I could f ind was that the thread on one of the metal caps used to cover the telescope when it's separated into three pieces had a couple of tiny pits on it (most people would never have noticed), and Astro-Physics replaced it quickly. The telescope is growing on me. Despite the relatively small aperture compared to Newtonian telescopes, there's something very appealing about the beautiful, clean view of the refractor, from low to high powers. And 35 years after using my original 60mm Tasco refractor with its German equatorial mount, I'm enjoying an equatorial mount again. Has it been worth waiting almost a decade for the telescope to arrive? It was for me. I was in no hurry, and I had another telescope. Today's shoppers can buy it used at the premium, buy a competitors or, if another telescope is available, go on the list for the Gran Turismo. I don't know how long you'd have to wait. g

4


Review: This Icy Orb Sure Gets a Lot of Attention
By Thomas Haeberle
On Valentine's Day, while I was wrapping up reading "The Pluto Files" by Dr. Neil deGrasse Tyson (W.W. Norton, $23.95), I came up with the equation that Tyson plus Pluto doesn't equal love. Tyson was thrown into the ring of controversy when the Hayden Planetarium, of which he's director, demoted Pluto to a side note in our solar system by excommunicating it as a planet in 2000. Tyson's superbly written book isn't just a dry accounting of events that led to Pluto's demotion, but a book full of color photos, jokes, cartoons, illustrations and e-mails from third graders to esteemed colleagues such as NASA's Alan Stern and Bill Nye the Science Guy. His support came from scientists, songwriters and comedians. Late-night TV comic Stephen Colbert pulled no punches when he feared what might happen "by taking away the specialness of Earth's planetness." He proceeded to trash talk the planet wanna-bes: "Hey Ceres, you're so ugly, God tried to hide you in an asteroid belt!" Amusing anecdotes abound. After Pluto's discovery in 1930, it influenced everything from cartoons to laxatives. Even physics made room for Pluto. In 1941, a team of physicists needed a name for a new element that had 94 protons. The newly discovered planet still loomed large so thus was born plutonium, the key element in the atomic bombs dropped on Japan. The chapters nicely divide into history, science, culture, politics and the aftermath of the excommunicated planet. Discussions are laced with e-mails, some longer than we need to read, while cartoonists spoof the controversy. Although at times humorous and lighthearted, Tyson gets somewhat cynical at those who disagreed with his approach on Pluto. But this is understandable when he recounts how the planetarium was renovated and the pains he took to insure the design was viable and changes would withstand any decision on a formal def inition of a planet. "We did something different. We looked across the solar system and asked ourselves what physical features of the planets and other objects could be taken and discussed as common properties. We used the giant Hayden sphere to make simple comparisons of how two families of objects in the solar system contrast with the Sun in size." What Tyson didn't expect was The New York Times article in January 2001and its impact on public perception of the new exhibits. A reporter hanging around the new planetarium almost a year after it opened heard a child asking his mother, "Where's Pluto?" Not long after that, the paper printed its infamous "Pluto Not a Planet" article. The dam had burst and Tyson's off ice was flooded with e-mails and phone calls. "It's always a little scary when the person who hired you calls you up and asks, `What have you done?' I was relatively new...and in charge of science content worth million of dollars of the museum's money." Tyson notes the exhibit was designed by consensus by persons within and outside the AMNH. He retraces this consensus to a panel he hosted in May 1999; recalling what he calls "the night of Pluto's fall from grace." Most panelists were divided on Pluto's status, but only one saw it destined for "uncompromising iceballhood." Jane Luu, co-discover of the f irst Kuiper Belt object, noted: "We are continuing to f ind more and more KBOs. What if we f ind one the same size or bigger [than Pluto]? Will these objects be called planets?" Eventually, Luu's implied prophesy came true. Astronomer Michael Brown discovered Eris, which is larger than Pluto. This put the burden on the International Astronomical Union to come up with a def inition. A planet-definition committee lacked specialists in the new frontiers of KBOs and exosolar planets. An initial def inition was redef ined and Pluto was left out in the cold. In the end chapter, the Plutologue, there is reconciliation with planetary scientist Mark Sykes, who fervently opposed demotion. During the "great planetary debate" at Johns Hopkins, no def inition was hammered out but both agreed the IAU had body-slammed Pluto but good. Regardless of whether you think Pluto's a planet, you're sure to f ind "The Pluto Files" absorbing and entertaining. g

Light Bill Introduced
Manhattan Democratic Assemblywoman Linda Rosenthal has introduced legislation (A5769) that provides authority to the State Department of Health to engage in or support research on the health effects of artif icial night light. Meghan Nutting, Rosenthal's legislative director, says her off ice is working on introducing other bills related to light pollution. 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.

5


Briefs: NASA, ESA Push Jupiter, Saturn Missions
NASA and the European Space Agency (ESA) are pushing ahead with proposals to send missions to explore Jupiter, Saturn and the many moons that circle them, the agencies announced last month. Both missions include sending multiple spacecraft. The f irst mission would be aimed at Jupiter. Dubbed the Europa Jupiter System Mission, it would send two orbiting spacecraft to study the planet and Io, Europa, Ganymede and Callisto in unprecedented detail. NASA would build one orbiter, the Jupiter Europa, while ESA would provide the other, Jupiter Ganymede. The spacecraft would launch in 2020 to reach Jupiter by 2026 and spend three years studying the planet and its moons. Like the Jupiter mission, the Saturn expedition would consist of NASA and European spacecraft. Dubbed the Titan Saturn System Mission, the flagship flight would include a NASA-built orbiter to study Saturn and its moons, as well as European lander and research balloon to continue exploration of Titan. Enceladus, which harbors ice-spewing geysers, is also a major target for that mission. Using NASA radar aboard India's Chandrayaan-1 spacecraft, scientists are getting their f irst look inside the Moon's coldest, darkest craters, where ice may be hiding. Images show the floors of permanently-shadowed polar craters not visible from Earth. The only way to explore such areas is to use orbital imaging radar. The images cover part of the Haworth crater at the south pole and the western rim of Seares crater near the north pole. Bright areas in each image represent surf ace roughness or slopes pointing toward the spacecraft. This is one of two NASA contributions to the Indian craft's payload. The other is the Moon Mineralogy Mapper, an imaging spectrometer that will provide the f irst map of the entire lunar surface at high spatial and spectral resolution. The Hubble Space Telescope has taken a snapshot of a picturesque planetary nebula in a distant cluster of stars within the Milky Way. The swirl of wispy green, red and blue hues spotlights nebula NGC 2818 in a star cluster some 10,000 light-years from Earth in the southern constellation Pyxis. NGC 2818 is one of very few planetary nebulae in our galaxy within an open cluster. Stars that form planetary nebulae typically live for billions of years. Hence, it's rare that an open cluster survives long enough for one of its members to form a planetary nebula. This open cluster is nearly 1 billion years old. The spectacular structure of NGC 2818 contains the outer layers of a Sun-like star that were sent into interstellar space during the star's f inal stages of life. The glowing gaseous shrouds were shed by the star after it ran out of fuel to sustain the nuclear reactions in its core. NASA's twin STEREO spacecraft are offering the f irst glimpse of the far side of the Sun, monitoring more than 270 degrees of solar longitude. Because the Sun rotates, all of it is seen from Earth over time. But at any given time, only half is visible. Scientists who monitor solar eruptions and the space storms they hurl toward Earth are eager to monitor the whole star 24/7. Seeing storms on the far side would improve forecasting. The two craft will be in their f inal positions in February 2011, 180 degrees apart and imaging the entire Sun all the time. That will match the next expected peak in solar activity. Because of how the Sun spins, STEREO will get a preview of sunspots and coronal holes before they rotate around and face Earth. A sharp-eyed instrument on the Very Large Telescope (VLT) has given astronomers a peek at the heart of a nearby galaxy, revealing a host of young, massive and dusty stellar nurseries and a possible twin of the Milky Way's supermassive black hole. The galaxy, NGC 253, is one of the brightest and dustiest spiral galaxies in the sky. Astronomers studied it in f iner detail in the near-infrared. Through an adaptive-optics system, features were revealed only 11 light-years across. With the images, astronomers identif ied 37 distinct bright regions, a threefold increase from previous results, packed into a tiny region at the core of the galaxy making up just 1% of the galaxy's size. These are probably active stellar nurseries. Astronomers also conclude that NGC 253's center hosts a scaled-up version of Sagittarius A*, the bright radio source that lies at the core of the Milky Way and is known to harbor a massive black hole. NASA and Google have teamed up to build the ultimate atlas for Mars fans eager to explore the planet in threedimensional detail. Google Mars 3D, a new mode included in Google's latest version of Google Earth software, allows users to tap into high-resolution, three-dimensional views of Martian terrain. The mode, which relies on NASA data and imagery from the Mars Reconnaissance Orbiter and other spacecraft, is designed so users can "fly" through Martian canyons in virtual mode and see the planet's surface through the eyes of the Spirit and Opportunity rovers, as well as other Mars missions. "They can fly to the top of Olympus Mons, the tallest volcano in our solar system, read geo-located excerpts about different locations on the planet from `A Traveler's Guide to Mars,' observe where various Mars rovers and landers have touched down and much more," Google said. The new Mars mode's sharing feature lets users add 3D content to the Mars map for all to see. Astronomers are seeing some frequent high-energy f ireworks from a stellar remnant 30,000 light-years away. Astronomy Briefs continued on page 7

6


Briefs: Smallest Exoplanet Orbits Sun-Like Star
Astronomy Briefs continued from page 6 The blasts arise from a rare type of neutron star known as a soft gamma-ray repeater. Such objects unpredictably send out a series of X-ray and gamma-ray flares. The object lies in the souther n constellation Nor ma. For two years, astronomers have identif ied pulsing radio and X-ray signals from it. The object is only the sixth known soft-gamma-ray repeater. In 2004, a giant flare from another soft-gamma-ray repeater affected Earth's upper atmosphere from 50,000 light-years away. Scientists think the source now is a spinning neutron star, the superdense remains of an exploded star. Images acquired when the latest flaring began show what appear to be expanding halos around the source. Multiple rings form as X-rays interact with dust clouds at different distances, with closer clouds producing larger rings. Both the rings and their apparent expansion are an illusion caused by the f inite speed of light and the longer path the scattered light must travel. X-rays from the brightest bursts scatter off of dust clouds between us and the star. The smallest extrasolar planet, less than twice the size of Earth, has been discovered orbiting a Sun-like star. Astronomers detected the planet as it transited its parent star. The host star is 457 light-years from Earth. This is the f irst time scientists have detected a planet that's "rocky" in the same sense as Earth. But to fully conf irm that status, they need to nail down its mass and radius. Scientists think it's terrestrial-like. It might have water ice or rocks, but it's certainly not a gas giant. The planet is an estimated 5.7-11 Earth masses. COROT-Exo-7b orbits its star every 20 hours. Its temperature is so high, (1,832-2,732 degrees), it could be covered in lava or water vapor. It may also belong to a class of planets thought to be made up of water and rock in almost equal amounts. Of the Earth-like planets detected, this is the f irst spotted using the transit method, which can yield mass and radius. Other methods just reveal the planet's mass. Astronomers have discovered a planet somewhat larger and more massive than Neptune orbiting a star 120 lightyears from Earth. While Neptune has a diameter 3.8 times that of Earth and a mass 17 times Earth's, HAT-P-11b, in Cygnus, is 4.7 times the size of Earth and has 25 Earth masses. HAT-P-11b was discovered because it passes directly in front of its parent star, blocking about 0.4 percent of the star's light. A number of Neptune-like planets have been found by radial-velocity searches, but HAT-P-11b is only the second Neptune-like planet found to transit its star, thus permitting precise determination of mass and radius. The world revolves once every 4.88 days. Its temperature is around 1,100 degrees. There are signs of a second planet in the HAT-P-11 system, but more radial-velocity data are needed to conf irm that. Gas-rich planets grew from a disk of dust and gas which eventually crumpled under its own gravitational instability, or so one theory goes. Now a computer simulation suggests this idea falls apart under turbulent forces within early protoplanetary systems. The old theory relies on the protoplanetary dust disk becoming denser and thinner until it reaches a tipping point, where it becomes gravitationally unstable and collapses into building blocks that form the basis for gas giants. But 3D modeling now shows that turbulence prevents the dust from settling into the dense disk necessar y for g ravitational instability to work. Scientists have long held dust in a protoplanetary disk ends up sandwiched between upper and lower layers of gas. But the model shows how gas layers flow at different speeds over and beneath the dust layer, which creates turbulence. Ripples prevent dust from ever settling into the thin, dense middle layer. It's been raining liquid methane on Titan, with images revealing a possible new lake in its south polar region. Scientists think the most plausible explanation is a lake f illed by recent rainfall. This conf irms the thinking of scientists who have suspected the presence of such lakes on Titan, caused by methane rain. Comparisons of the south pole images with those of the north pole conf irmed greater stores of liquid methane in the northern hemisphere. Some known north polar lakes are large. If full, Kraken Mare, 154,000 square miles, would be almost f ive times the size of Lake Superior. One remaining question is whether such lakes could resupply Titan's atmosphere with hydrocarbons over geological time scales. Over time, chemical reactions in Titan's atmosphere destroy the hydrocarbons. Combined with previous analyses, new observations suggest underground methane reservoirs must exist. Plumes of methane gas detected over certain locations on Mars in 2003 could point to active geological processes on the planet, or perhaps even to methane-burping microbes deep below the Martian surface, a new study reports. A search conducted with three ground-based telescopes that covered 90% of the surface over three Mars years (seven Earth years) detected extended plumes of methane that varied by season and seemed to emanate from specif ic locations. Release of methane is likely connected to heating that happens as summer progresses in the northern hemisphere. The methane could come from deeper below the surface or could be released by geochemical processes nearer the surface. The most tantalizing possibility is that methane comes from subsurface Martian microbes. Outside of the plumes, methane concentrations were very low, showing the gas didAstronomy Briefs continued on page 10

7


Astronomy Briefs continued from page 7 n't get very far or last very long in the atmosphere. Oxidation could be destroying the methane and peroxidecoated dust grains lofted into the air could be eating away at it. An asteroid the size of a small house is slowly passing through space and was recently less than twice as far away as our Moon. Although the recently discovered rock poses no immediate threat, it will hang around. The asteroid, 2009 BD, is an oddity. Astronomers think it might be a co-orbital asteroid, "circling the Sun in near-tandem with our planet," according to Spaceweather.com. Estimates of its orbit keep it at about 9.3 million miles from Earth through November 2010. The rock, 33 feet in diameter, was some 400,000 miles away at its closest approach January 25. NASA's plans for the mammoth Ares V rocket could do more than just launch lunar landers and cargo to the Moon. It could haul massive space telescopes that dwarf the Hubble or fling deep space probes on faster missions to outer planets. Slated to make its f irst test flight in 2018, Ares is designed to launch payloads weighing almost 180 metric tons into low-Earth orbit. The rocket presents a boon for astronomers dreaming of bigger, better space-based observatories. Possible missions include planetary probes to the Sun, Neptune and Titan. The rocket could even humble the James Webb Space Telescope slated to launch in 2013. The 33-foot payload shroud for Ares allows extra space for space telescopes with larger main mirrors. Hubble's main mirror, for example, is about 7.8 feet across. Ares V could f it an observatory three times larger, like the proposed 26foot Monolithic Space Telescope, which would be able to observe objects in space 11 times fainter and with three times the sharpness of Hubble. Even larger space telescopes could be packed atop the rocket if their mirrors were folded up for launch. Was the far side of the Moon always unseen? Two French geologists postulate that the Moon was once rotated 180 degrees, with the current far side of the moon facing Earth. As reported in Scientific American, they say a large impact roughly 4 billion years ago could have temporarily disrupted the Moon's rotation, allowing it to eventually settle back into so-called spin-orbit synchrony either in its original orientation or rotated 180 degrees. Two groups of astronomers have detected atmosp h e r e s o f ex o p l a n e t s f r o m g r o u n d - b a s e d t e l e s c o p e s . Previous observations had been almost entirely by spacebased instruments. Astronomers have detected key gases, including carbon dioxide, water vapor, silicates and sodium. Planet OGLE-TR056b, a hot Jupiter, sits about 5,000 lightyears away in the direction of the center of our galaxy. The

planet's atmosphere is more than 4,400 degrees. There's little to no cloud cover and a static atmosphere with little circulation. Another team detected thermal emission in the near infrared of another exoplanet, TrES-3b. Its atmosphere is about 3,000 degrees. Moon rocks delivered to Earth by Apollo 17 astronauts held a mystery: Why were the rocks magnetic? MIT scientists think they have an answer. Some 4.2 billion years ago, the Moon had a liquid core with a dynamo that produced a strong magnetic f ield. The magnetic f ield would have been about 1/50th as strong as Earth's today. The team found evidence for the molten-core theory by analyzing the oldest Moon rocks that haven't been subjected to major shocks from later impacts, something that tends to erase evidence of earlier magnetic f ields. The rocks are older than any known rocks from Mars or Earth. The rocks were collected during the last lunar landing mission, Apollo 17. g Imaging continued from page 1 Image Transport System (FITS) to an FTP folder at the site for future downloads to your computer. The FITS format f iles have to be converted for processing with Photoshop or similar software. If you aren't available at a certain time, use of a telescope can be reserved in advance and an automatic preloaded program or "script" run without you being online. Some images I've processed are posted in the Members Galleries on the club's website (www.aaa.org) at Ed Fox GRAS (Global-Rent-A-Scope) and Light Bucket galleries. As a f irst-time user of astrophotography equipment, I had to feel my way through some of the process. But it couldn't have been easier, when given the initial advice to use the "oneclick" option. All I had to do was choose a telescope, select a target from a displayed list and let it happen. The automatic script plays out on the screen and you can follow the process, as it slews, focuses with test exposures and eventually does the f inal exposure. After a few one-click images, I was making exposures using a variety of f ilters. With a little research and some advice from fellow club members, I learned how to process those images using Photoshop. But that's another story. Naturally, using a remote scope on a rental basis wasn't the same as taking your own scope to a dark-sky site and exposing it to target your own trophy image. But it was a great way to be introduced to the process, especially on a snowy day. Referenced web sites: www.global-rent-a-scope.com; www.lightbuckets.com. g

8


Events on the Horizon March 2009
M: members; P: open to the public; T: bring your telescopes, binoculars, etc.; C: cancelled if cloudy; HQ: at AAA headquarters, Dowbtown 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 Wednesdays March 4, 11 and 25, and Saturdays March 7, 14, 21 and 28, 8:30-10:30 p. m. Observing at Inwood Hill Park, Manhattan, P, T, C Next dates: April 1, 8, 22, 29. Tuesday, March 10, 7:30 p. m. 2009 Isaac Asimov Memorial Debate, P, AMNH Hayden Planetarium director Neil deGrasse Tyson will moderate "From Planets to Plutoids--Our New Solar System" in the LeFrak Theater of the AMNH (enter at 77th Street). The panel will consist of NASA's Alan Stern and Jack Lissauer, the University of Hawaii's David C. Jewitt, the University of California Berkeley's Gibor Basri, The Planetary Science Institute's Mark V Sykes and MIT's . Sara Seager. Thursday, March 12, 6 to 8:30 p. m. Recent Advances in Astronomy Seminar, Room 801, 239 Greene Street, M Discussion of new f indings in astronomy and astrophysics. Dark energy will be among the topics. Next date: April 9. Friday, March 13, 6:15-8 p. m. AAA lecture, free, P Hayden Planetarium director Dr. Neil deGrasse Tyson will discuss "The Rise and Fall of Pluto--Witness to Demotion" in the Kaufmann Theater of the AMNH. This is the AAA's annual John Marshall Memorial Lecture. Next AAA lecture: April 3. Friday, March 13, 8-10 p. m. Observing at Floyd Bennett Field, Brooklyn, P, T, C Brit continued from page 3 would not be bettered for decades. Harriot lived from 1560 to 1621. He studied at St Mary's Hall, Oxford, achieving his BA in 1580. He then became a mathematical teacher and companion to the explorer Sir Walter Raleigh. In the early 1590s Raleigh fell from royal favor and was imprisoned in the Tower of London. Harriot was passed to the patronage of On the model airplane flying f ield. Next date: April 3. Wednesday, March 18, 8: 30-10:30 p. m. Observing at The Cloisters, Fort Tryon Park, Manhattan, P. T, C Next date: April 15. Saturday, March 14, 7:30 p. m. Custer Institute and Observatory, Southold, NY, lecture, P Alan Calder, astrophysics professor at Stony Brook University, will discuss "Nature's Beacons: Type Ia Supernovae," including how they're simulated in the lab. Info: www.CusterObservatory.org. Saturday, March 28, 10-noon Solar Observing, Central Park, P At the Conservatory Waters. Next date: April 25. Saturday, March 28, 7:30 p. m. Custer Institute and Observatory, Southold, NY, lecture, P Telescope historian Edward Furey will discuss "The History of the Telescope." Info: www.CusterObservatory.org. Tuesday, March 31, 7-9 p. m. Observers' Group, M, HQ Upcoming celestial events, astronomy resources on the Internet, using telescopes and binoculars. Weather permitting, after the meeting we'll go to a nearby park for observing. Next date: April 28. Henry Percy, the Ninth Earl of Northumberland who was himself imprisoned as one of the Gunpowder Plotters in 1605 but continued to support Harriot in his residence at Sion (now Syon) Park, in what is now west London. Harriot became a leading force in mathematics, Chapman explained, working on algebraic theory and corresponding with scientists across Europe. Brit continued on page 10

9


Brit continued from page 9 By 1609, Harriot had acquired his f irst "Dutch tr unke" (telescope), which had been invented in the Netherlands. He turned it on the Moon on July 26, becoming the f irst astronomer to draw an astronomical object after viewing it through a telescope. The crude sketch shows a rough outline of the lunar terminator (the line marking the division between night and day on the Moon, as seen from the Earth) and includes a handful of features like the dark areas Mare Crisium, Mare Tranquilitatis and Mare Foecunditatis. Harriot went on to produce more maps from 1610 to 1613, Chapman said. Not all are dated, but they show an increasing level of detail. By 1613, he had created two maps of the whole Moon, with many identif iable features such as lunar craters depicted in their correct relative positions. The earliest telescopes of the kind used by Harriot, and Galileo, had a narrow f ield of view, meaning that only a small portion of the Moon could be seen at one time and making this work all the more impressive. No better maps would be published for several decades. Despite his innovative work, Harriot remains relatively unknown. Unlike Galileo, he didn't publish his drawings. And unlike Galileo, Harriot isn't being widely celebrated

during 2009, dubbed the International Year of Astronomy as a commemoration of the telescope's 400th year. Chapman attributed this to his comfortable position as a "well-maintained philosopher to a great and wealthy nobleman" with a generous salary, said to be "several times the level of the warden of Wadham College, Oxford." Galileo, interestingly, was unable to buy a telescope. So he f igured out the optics and built his own. He also examined the Moon, then found the Milky Way was composed of individual stars. Galileo also discovered four moons around Jupiter and observed and drawing sunspots. "Thomas Har riot is an unsung hero of science," Chapman said. "His drawings mark the beginning of the era of modern astronomy we now live in, where telescopes large and small give us extraordinary information about the universe we inhabit." Professor Andy Fabian, President of the Royal Astronomical Society, agrees. I can only...mar vel at the work of 17th centur y astronomers like Thomas Harriot. The world is right to celebrate Galileo in the International Year of Astronomy--but Harriot shouldn't be forgotten!" g

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

Forwarding and Address Correction Requested

First Class