Space - Tullamore Astronomical Society

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crust (read the article about Apophis and a likely Earth impact in 2036 in the Sept/Oct 2005 issue of Réalta –Ed.). Earth's Moon, on the other hand, is pockmarked with millions of craters because it lacks both atmosphere and geologic activity. Similarly, Mars has thin atmosphere and relatively little geologic activity. On both the Moon and Mars, teasing out the primary impacts from the secondaries is difficult because the craters are just too numerous. The researchers instead turned to Europa and a world covered in a thick crust of ice. More importantly, Europa is geologically active like Earth. Its surface is constantly being repaved with new ice and as a result, Europa has very few craters. Using high-resolution images from NASA's Galileo spacecraft, the researchers measured the number, size and distribution of craters on Europa. They then ran a computer simulation of meteors randomly striking Europa but with the condition that the number and size of the craters had to match the real number and size observed in the images. After running the simulations hundreds of times and comparing the results to the images, they found that the crater distributions were not similar as would be expected if most of the craters were caused by primary impacts. The finding is important because scientists typically use crater counts to date the ages of planet and moon surfaces. When comparing two similar regions on a moon, for example, scientists generally assume that the region with more impact craters is older. Scientists can also use a region's crater density to calculate it's absolute age. They usually use our own Moon as a reference because scientists have reliably dated the age of some its craters based on rocks brought back by astronauts. If it turns out that most of these small caters are secondary and not primary, then that means the calibrated age from our Moon is not right. Most of the objects that strike Jupiter and its moons come from a region of the Solar System known as the Kuiper Belt. Therefore, another implication of the finding may be that there are fewer small asteroids in the Kuiper Belt than previously thought. It may be that small asteroids are rarely made or perhaps some process depletes them before they can reach Jupiter and its moons. Life's Building Blocks 'Abundant in Space' The idea that comets and meteorites seeded an early Earth with the tools to make life has gained momentum from recent observations of some of these building blocks floating throughout the cosmos. Scientists scanning a galaxy 12 million light-years away with NASA's Spitzer Space Telescope detected copious amounts of nitrogen containing polycyclic aromatic hydrocarbons (PANHs), molecules critical to all known forms of life. PANHs carry information for DNA and RNA and are an important component of haemoglobin, the molecule that transports oxygen through the body. They also make chlorophyll, the main molecule responsible for photosynthesis in plants, and perhaps most importantly, they're the main ingredient in caffeine and chocolate. "There once was a time that the assumption was that the origin of life, everything from building simple compounds up to complex life, had to happen here on Earth," said study leader Doug Hudgins of Ames Research Center. "We've discovered that some very biologically interesting molecules can be formed outside our earthly environment and delivered here." While organic compounds have been discovered in meteorites that have landed on Earth, this is the first direct evidence for the presence of complex, important biogenic compounds in space. So far evidence suggests that PANHs are formed in the winds of dying stars and spread all over interstellar space. "This stuff contains the building blocks of life, and now we can say they're abundant in space," Hudgins said. "And wherever there's a planet out there, we know that these things are going to be raining down on it. It did here and it does elsewhere." Using the Spitzer Space Telescope, Hudgins and his colleagues detected the familiar chemical signature of regular polycyclic aromatic hydrocarbons (PAHs) in the spiral galaxy M81, as well as a similar, but unknown signature. "There were a few anomalies in the spectrum that we couldn't explain," Hudgins says. The researchers compared their readings to the infrared signatures of similar molecules, finally settling on nitrogen containing PANHs because their data showed there was nitrogen in the regions they were investigating. "When we did that, we found that by putting a little nitrogen in these molecules explained the troubling molecules," Hudgins said. "This discovery takes this reservoir of molecules that we didn't think were interesting and transforms all this stuff into something of biologic interest." 6 Réalta – Volume 7, Issue 2 – November/December 2005 – Tullamore Astronomical Society
Moon discovered orbiting Solar System's 10th planet The newly discovered 10th planet, 2003 UB313, is looking more and more like one of the Solar System's major players. It has the heft of a real planet (latest estimates put it at about 20 percent larger than Pluto), a catchy code name (Xena, after the TV warrior princess), and a Guinness Book-ish record of its own (at about 97 astronomical units-or 9 billion miles from the sun, it is the Solar System's farthest detected object). And, astronomers from the California Institute of Technology and their colleagues have now discovered, it has a moon. The discovery of the moon of the 10th planet from the W.M. Keck Observatory. The planet appears in the centre, while the moon is the small dot at the 3 o'clock position. The moon, 100 times fainter than Xena and orbiting the planet once every couple of weeks, was spotted on September 10, 2005, with the 10-meter Keck II telescope at the W.M. Keck Observatory in Hawaii by Michael E. Brown, professor of planetary astronomy, and his colleagues at Caltech, the Keck Observatory, Yale University, and the Gemini Observatory in Hawaii. "Since the day we discovered Xena, the big question has been whether or not it has a moon," says Brown. "Having a moon is just inherently cool-and it is something that most self-respecting planets have, so it is good to see that this one does too." Brown estimates that the moon, nicknamed "Gabrielle"-after the fictional Xena's fictional sidekick-is at least one-tenth of the size of Xena, which is thought to be about 2700 km in diameter (Pluto is 2274 km), and may be around 250 km across. To know Gabrielle's size more precisely, the researchers need to know the moon's composition, which has not yet been determined. Most objects in the Kuiper Belt, the massive swath of miniplanets that stretches from beyond Neptune out into the distant fringes of the solar system, are about half rock and half water ice. Since a half-rock, half-ice surface reflects a fairly predictable amount of sunlight, a general estimate of the size of an object with that composition can be made. Very icy objects, however, reflect a lot more light, and so will appear brighter-and thus bigger-than similarly sized rocky objects. Further observations of the moon with the Hubble Space Telescope, planned for November and December, will allow Brown and his colleagues to pin down Gabrielle's exact orbit around Xena. With that data, they will be able to calculate Xena's mass, using a formula first devised some 300 years ago by Isaac Newton. "A combination of the distance of the moon from the planet and the speed it goes around the planet tells you very precisely what the mass of the planet is," explains Brown. "If the planet is very massive, the moon will go around very fast; if it is less massive, the moon will travel more slowly. It is the only way we could ever measure the mass of Xena-because it has a moon." The researchers discovered Gabrielle using Keck II's recently commissioned Laser Guide Star Adaptive Optics system. Adaptive optics is a technique that removes the blurring of atmospheric turbulence, creating images as sharp as would be obtained from space-based telescopes. The new laser guide star system allows researchers to create an artificial "star" by bouncing a laser beam off a layer of the atmosphere about 75 miles above the ground. Bright stars located near the object of interest are used as the reference point for the adaptive optics corrections. Since no bright stars are naturally found near Xena, adaptive optics imaging would have been impossible without the laser system. "With Laser Guide Star Adaptive Optics, observers not only get more resolution, but the light from distant objects is concentrated over a much smaller area of the sky, making faint detections possible," says Marcos van Dam, adaptive optics scientist at the W.M. Keck Observatory, and second author on the new paper. The new system also allowed Brown and his colleagues to observe a small moon in January around 2003 EL61, code-named "Santa," another large new Kuiper Belt object. No moon was spotted around 2005 FY9-or "Easterbunny"-the third of the three big Kuiper Belt objects recently discovered by Brown and his colleagues using the 48-inch Samuel Oschin Telescope at Palomar Observatory. But the presence of moons around three of the Kuiper Belt's four largest objects- Xena, Santa, and Pluto-challenges conventional ideas about how worlds in this region of the solar system acquire satellites. Previously, researchers believed that Kuiper Belt objects obtained moons through a process called gravitational capture, in which two formerly separate objects moved too close to one another and become entrapped in each other's gravitational embrace. This was thought to be true of the Kuiper Belt's small denizens-but not, however, of Pluto. Pluto's massive, closely orbiting moon, Charon, broke off the planet billions of years ago, after it was smashed by another Kuiper Belt object. Xena's and Santa's moons appear best explained by a similar origin. "Pluto once seemed a unique oddball at the fringe of the solar system," Brown says. "But we now see that Xena, Pluto, and the others are part of a diverse family of large objects with similar characteristics, histories, and even moons, which together will teach us much more about the solar system than any single oddball ever would." Réalta – Volume 7, Issue 2 – November/December 2005 – Tullamore Astronomical Society 7
Page 1 and 2: REALTA 9+- Reviews, Events And Lect
Page 3 and 4: Key organisers and folks involved i
Page 5: NEWS UPDATE From Around The Univers
Page 9 and 10: Two New Moons for Pluto? New images
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Page 13 and 14: Great Irish Women Astronomers By Gi
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Page 17 and 18: Goldilocks and the (many) more than
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Page 21 and 22: SPACEFLIGHT News Russian Spacecraft
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