The title of yesterday's post -- 'The Odds on Centauri' -- would fit well with today's musings. Alpha Centauri makes us ponder the odds not just in terms of interstellar bets and future space probes, but also in terms of the likelihood of life around these stars. And after all, 2008 saw significant work on this question, including the contributions of Philippe Thébault (Stockholm Observatory) and colleagues, whose studies of Centauri A and B show that while stable planetary orbits exist there, the odds on those planets forming in the first place are long. Greg Laughlin (UC-Santa Cruz) isn't necessarily daunted by this work (he explains why here), but the planet-hunter extraordinaire is realistic about life-bearing planets in this environment, and even more judicious about the possibility of a technological society making its home in the system. The question rises naturally out of recent publicity given the 20th Century Fox film The Day the Earth Stood Still, in which it was...

A new camera called OPTIC (Orthogonal Parallel Transfer Imaging Camera), built at the University of Hawaii, has clarified our view of the distant world known as WASP-10b. Transits are helpful because they allow us to measure the size of the observed planets, and in this case, WASP-10b turns out to be not one of the most bloated exoplanets yet found, as once thought, but one of the densest. Orbiting some 300 light years from Earth, the planet's diameter is now known to be only six percent larger than Jupiter's, although it is three times more massive, with a corresponding density three times that of Jupiter. OPTIC is mounted on the University of Hawaii's 2.2-meter telescope on Mauna Kea. If you compare what it can do with its highly sensitive and stable detector to the best results from charge-coupled devices (CCDs), you find a photometric precision two to three times higher. According to this news release from the university's Institute for Astronomy, that's comparable to the most...

The Kepler mission launches March 5, a date to circle on your calendar. Kepler may become the first instrument to detect an Earth-size planet in the habitable zone of another star, using the transit method to examine 100,000 stars in its 3.5 year mission. The 0.95-meter diameter telescope is now at Ball Aerospace & Technologies (Boulder, CO), having passed the necessary environmental tests that demonstrate its space-worthiness. And word has just come that it has also passed the necessary 'pre-ship review' for transit to Florida in January. Image: An artist's rendering of what our galaxy might look like as viewed from outside. Our sun is about 25,000 light years from galactic center. The cone illustrates the neighborhood of our galaxy that the Kepler Mission will search to find habitable planets. Credit: Jon Lomberg. The image above, the work of the fine space artist Jon Lomberg, gives an idea of where Kepler will be looking. As always, Lomberg (creator of the gorgeous Galaxy Garden...

The nice thing about our conventional idea of a habitable zone is that liquid water can exist on the surface. The less helpful part of that definition is that water is more readily available much further out in a planetary system, where it usually shows up as ice. Think in terms of the 'ice line,' or the 'snow line.' Beyond it is the area around the still-forming star where temperatures are low enough to allow hydrogen compounds to condense into ice grains. Of course, we're living proof of the fact that planets in the inner system can be covered with oceans. It's therefore plausible to think in terms of delivery mechanisms, with icy comets bombarding planets in the inner system to produce oceans like those on Earth. But we're learning to extend our reach beyond conventional habitable zone notions to places much further out, an idea recently given credence by divers hands. Consider the work of Scott Gaudi (Ohio State), Eric Gaidos (University of Hawaii) and Sara Seager (MIT), familiar...

The prospect of habitable planets around red giant stars fires the imagination, enough so that quite a few readers forwarded me the link to a recent paper looking at this question. I'm reluctant to speak for others, but I suppose a major reason we're so interested (and I, too, had flagged the paper as soon as it popped up on the arXiv server) is that it changes our view of habitable worlds once again. Not long ago it was only the G-class, Sun-like star that seemed a likely abode of life. Then we started looking hard at M-dwarfs. Do we now extend the search to massive red giants, the descendants of stars once like our own? Image credit: NASA, ESA and A. Feild (STScI). Werner von Bloh (Potsdam Institute for Climate Impact Research) and team show that the possibility is real. We've long known that life on a planet in Earth's orbit would not survive the swelling of the Sun, even if it did not actually engulf the planet. But life on Earth would actually die out long before that event, if...

It's tantalizing to speculate that there might be a brown dwarf system nearer to us than the Alpha Centauri stars. The odds seem long, but the discovery of a pair of brown dwarfs that are each no more than a millionth as bright as the Sun makes for exciting reading. The objects were originally cataloged by the Two Micron All Sky Survey (2MASS) as a single brown dwarf identified as 2MASS J09393548-2448279, but Adam Burgasser (Massachusetts Institute of Technology) has been able to show that the 'object' is actually a pair of the faint dwarfs. Here the Spitzer Space Telescope was the instrument of choice, showing that 2M 0939's brightness was twice what would have been expected from its temperature, which was determined to be in the range of 565 to 635 Kelvin (560 to 680 degrees Fahrenheit). The implication was that this is a brown dwarf binary, two dwarfs each with a mass some thirty to forty times that of Jupiter. And while the objects are a million times fainter than the Sun in...

Among the many things that boggle my mind is the fact that we can learn things about the atmosphere of planets that we can't even see. Take well-studied HD 189733b, a gas giant in close orbit around a K2-class star some 63 light years from us. No one has ever laid eyes on this beast, either in infrared or optical light. But that's of little moment to the Hubble telescope, among whose tools is NICMOS -- the Near Infrared Camera and Multi-Object Spectrometer. It and a lot of ingenuity get results. A transiting planet like HD 189733b moves behind its parent star every two days or so. When that happens, light from the star itself (the planet now being behind the star) can be compared to the combined light of planet and star when both are facing the Earth. Any emissions from the planet can be examined, a useful window into its atmosphere. Using such techniques, Mark Swain (Jet Propulsion Laboratory) and team have been able to detect carbon dioxide and carbon monoxide on this world, which...