We may not have images of terrestrial planets around another star yet, but many things can be learned about such worlds by computer simulation. A team of British astronomers, for example, has examined known exoplanetary systems in hopes of isolating those in which Earth-like worlds could exist in stable and habitable orbits. This is tricky business, because the massive planets present in almost every exoplanetary system we know about could disrupt such orbits long before life might have a chance to form on any worlds there. It's also tricky because to determine which systems could have life-bearing planets requires you to figure out the location of the habitable zone in each. Researchers Barrie Jones, Nick Sleep and David Underwood (Open University, Milton Keynes, UK) here use the classical definition of habitable zone: the distances from a star where water at the surface of an Earth-like planet would be in liquid form. Not surprisingly, they find that the question of planetary...

A starshade shaped like a daisy? Centauri Dreams remains entranced with the concept, known as New Worlds Imager and now getting renewed attention thanks to the efforts of astronomer Webster Cash (University of Colorado, Boulder). We've seen before that Cash is hoping to land a NASA Discovery-class mission for a starshade that would block the light of a nearby star to reveal the planets around it. The starshade would work in tandem with a telescope mounted on a separate spacecraft 15,000 miles away, with the shade being moved as needed to place it into the line of sight of stars of interest. The result: the ability to image planetary systems including terrestrial worlds, and even to analyze exoplanetary atmospheres. Cash's latest thoughts on the subject appear in the July 6 issue of Nature, where he describes a starshade some 50 yards in diameter and its associated space telescope. Both could be launched into an orbit roughly a million miles from Earth, where shade and telescope could...

So much good material has run lately on planet-hunter Gregory Laughlin's systemic site that Centauri Dreams feels seriously remiss in returning to it so infrequently. So there is catching up to do, but we focus today on Laughlin's new work, with UCSC graduate student Jeremy Wertheimer, on an intriguing question about Proxima Centauri. Is the tiny star in fact gravitationally bound to Centauri A and B? Surprisingly, much recent work has suggested otherwise, including a 1993 paper by Robert Matthews and Gerard Gilmore that set the tone for Proxima research in that decade. But Laughlin notes that the European Space Agency's Hipparcos satellite has firmed up our knowledge of the position, distance and velocity of nearby stars, enough to demand a new look at this question. After all, Proxima is roughly 15,000 AU from the Centauri binaries, and shows only a small velocity relative to them. It would seem unlikely these stars would not be bound into a triple system, and Laughlin and...

Back in 2003, while researching Centauri Dreams, I interviewed physicist Geoffrey Landis at Glenn Research Center in Cleveland. At that time, Landis' office was packed with Mars images, apropos for a man who had done so much work on rover technology. I asked him whether, after all this study, Mars had taken on the aspect of a real place to him, like Cleveland. Not surprisingly, he said that it had, and he credited 3-D images from Mars Pathfinder for that. Wearing glasses, Landis said, "It was as if you were standing on Mars. You could see ups and downs, ridges and valleys. That changed the view of Mars from another planet to a place you could go out and walk around." We're a long way from 3-D close-ups, but I suspect some astronomers are starting to feel that way about Beta Pictoris, a young star some 63 light years away in the southern constellation Pictor that first drew attention to itself because of excess infrared radiation. A warm circumstellar disk was surely the cause, and...