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Thu, 12 Nov 2009 Astronomers have identified an easy-to-measure chemical fingerprint for determining which sunlike stars are likely to host planets. The marker—a low abundance of lithium in the atmosphere of these stars—could prove an invaluable guide for planet hunters trying to determine which of the myriad sunlike stars to select for long-term study. In their study, Garik Israelian of the Instituto de Astrofísica de Canarias in Tenerife, Spain, and his colleagues relied on data from a census of 133 sunlike stars, most of them monitored for several years with the European Southern Observatory's HARPS spectrograph at the La Silla observatory in Chile. Tiny wobbles in the motions of 30 of these stars indicate the gravitational tug of unseen planets. In the Nov. 12 Nature, Israelian and his colleagues report that the majority of sunlike stars hosting planets in the HARPS sample have, on average, one-tenth the amount of lithium of those without planets. It's been known for decades that Earth's sun shows such a depletion. Tue, 20 Oct 2009 European astronomers have found 32 new planets outside our solar system, adding evidence to the theory that the universe has many places where life could develop. Scientists using the European Southern Observatory telescope didn't find any planets quite the size of Earth or any that seemed habitable or even unusual. But their announcement increased the number of planets discovered outside the solar system to more than 400. Six of the newly found planets are several times bigger than Earth, increasing the population of so-called super-Earths by more than 30 percent. Most planets discovered so far are far bigger, Jupiter-sized or even larger. Thu, 17 Sep 2009 Astronomers have finally found a place outside our solar system where there's a firm place to stand—if only it weren't so broiling hot. As scientists search the skies for life elsewhere, they have found more than 300 planets outside our solar system. But they all have been gas balls or can't be proven to be solid. Now a team of European astronomers has confirmed the first rocky extrasolar planet. Scientists have long figured that if life begins on a planet, it needs a solid surface to rest on, so finding one elsewhere is a big deal. "We basically live on a rock ourselves," said co-discoverer Artie Hatzes, director of the Thuringer observatory in Germany. "It's as close to something like the Earth that we've found so far. It's just a little too close to its sun." Wed, 29 Jul 2009 Exobiologists are looking for every conceivable sign of alien life and habitable planets. But there may be clues that few have thought of. Taylor Perron, a geophysicist at the Massachusetts Institute of Technology, thinks his research team has found one in the familiar, repeating pattern of ridges and valleys that shape many landscapes on Earth. Their report, published July 23 in the journal Nature, shows that the activity of living creatures help sculpt their terrain. It helps establish the spacing between ridges and valleys. Wed, 3 Jun 2009 Researchers for half a century have tried—and failed—to use the motion of stars moving across the sky to discover planets that lie beyond the solar system. Now a team has finally used the method, known as astrometry, to find one of these orbs. The newfound extrasolar planet, six times heavier than Jupiter, orbits the low-mass star VB 10 some 20 light-years from Earth ... The traditional method of identifying extrasolar planets ... relies on tracking the velocity of a parent star along the line of sight to Earth—rather than across the sky. Because an orbiting planet pulls its parent star ever so slightly to and fro, the star's line-of-sight motion speeds up and slows down periodically, revealed by telltale shifts in the color of starlight recorded from Earth. This technique, known as the wobble or Doppler shift method, detects heavyweights that lie close to their star most easily ... In contrast, the astrometric method ... pins down the exact mass of a planet. The method favors massive planets that lie far from a parent star, since such planets cause a star to move by the largest amount across the sky. Mon, 1 Jun 2009 The nearest Earth out there in space? It might be right next door, galactically speaking. Two teams of astronomers, one from the United States and one from Europe, are in a race to find a planet orbiting our near neighbors Alpha Centauri A and Alpha Centauri B, twin stars that appear from Earth as a single point of light. "I'm betting that there are planets like Earth or Mars or Venus around either or both of those stars, and the only question is whether we'll be able to detect them," said Debra Fischer, an astronomer at San Francisco State University. Backed with U.S. government funding, she is using a telescope in Chile to assemble 100,000 observations of the Centauri system. Thu, 21 May 2009 ...Astronomers have always suspected that planets might orbit stars other than our sun. We imagined, though, that we would find systems much like our own solar system, centered on a star much like the sun. Yet when a flood of discoveries began 15 years ago, it was apparent right away that extrasolar planetary systems can differ dramatically from our solar system. The first example was the sunlike star 51 Pegasi, found to have a planet more massive than Jupiter on an orbit smaller than that of Mercury. As instruments became more sensitive, they found ever stranger instances. The sunlike star HD 40307 hosts three planets with masses between four and 10 Earth masses, all on orbits less than half the size of Mercury's. The sunlike star 55 Cancri A has no fewer than five planets, with masses ranging from 10 and 1,000 Earth masses and orbital radii ranging from one tenth that of Mercury to about that of Jupiter. Planetary systems imagined in science fiction scarcely compare. Wed, 13 May 2009 Things were not looking so good for alien life in 1976, after the Viking I spacecraft landed on Mars, stretched out its robotic arm, and gathered up a fist-size pile of red dirt for chemical testing. Results from the probe's built-in lab were anything but encouraging. ... What a difference 33 years make. Back then, Mars seemed the only remotely plausible place beyond Earth where biology could have taken root. Today our conception of life in the universe is being turned on its head as scientists are finding a whole lot of inviting real estate out there. As a result, they are beginning to think not in terms of single places to look for life but in terms of "habitable zones"—maps of the myriad places where living things could conceivably thrive beyond Earth. Such abodes of life may lie on other planets and moons throughout our galaxy, throughout the universe, and even beyond. Tue, 12 May 2009 One of the most remarkable features of the solar system is the variety of planetary atmospheres. Earth and Venus are of comparable size and mass, yet the surface of Venus bakes at 460 degrees Celsius under an ocean of carbon dioxide that bears down with the weight of a kilometer of water. Callisto and Titan—planet-size moons of Jupiter and Saturn, respectively—are nearly the same size, yet Titan has a nitrogen-rich atmosphere thicker than our own, whereas Callisto is essentially airless. What causes such extremes? If we knew, it would help explain why Earth teems with life while its planetary siblings appear to be dead. Knowing how atmospheres evolve is also essential to determining which planets beyond our solar system might be habitable. Wed, 22 Apr 2009 The most Earth-sized planet and the most temperate planet known beyond our solar system both circle a dim red star 21 light-years away. These discoveries, announced yesterday at a meeting in England, moved astronomers a step closer to their dreams of finding other planets capable of supporting life as we understand it. Since 1995, scientists have found more than 350 planets orbiting other stars, but most suffer from the same problems that make our neighbors in the solar system so inhospitable. Many of the so-called extrasolar planets orbit so close that their stars would sterilize their surfaces. Others are jumbo "gas giants," like Jupiter, and therefore unlikely to have solid surfaces. Astronomers suspect that Earthlike planets are out there but that they are nearly impossible to detect with current technology. Wed, 22 Apr 2009 In the search for Earth-like planets, astronomers zeroed in on two places that look awfully familiar to home. One is close to the right size. The other is in the right place. European researchers said they not only found the smallest exoplanet ever, called Gliese 581 e, but realized that a neighboring planet discovered earlier, Gliese 581 d, was in the prime habitable zone for potential life. "The Holy Grail of current exoplanet research is the detection of a rocky, Earth-like planet in the 'habitable zone,'" said Michel Mayor, an astrophysicist at Geneva University in Switzerland... Gliese 581 e is only 1.9 times the size of Earth—while previous planets found outside our solar system are closer to the size of massive Jupiter, which NASA says could swallow more than 1,000 Earths. Every weekday, Sigma Xi, the Scientific Research Society, selects a set of significant and interesting science-related news articles from the mainstream media. The news stories featured here are selected from Sigma Xi's daily Science in the News e-mail. http://www.mediaresource.org/news.instruct.shtml |
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