Epsilon Eridani was a magic name in my childhood, so convinced was I that the nearby star (10.5 light years from Earth) was orbited by planets. Now the Hubble Space Telescope has weighed in with definitive evidence for the existence of at least one of those worlds, a Jupiter-class gas giant in a 6.9 year orbit around the star. The planet was originally detected in 2000 by radial velocity measurements, but there was still the faint possibility that turbulence on the star itself might mimic a planet's effects. Now we know that wasn't so. G. Fritz Benedict and Barbara McArthur (University of Texas at Austin) led the team that announced the result. Those stellar wobbles tell an unmistakable story when observed over time. Here's Benedict on the matter: "You can't see the wobble induced by the planet with the naked eye. But Hubble's fine guidance sensors are so precise that they can measure the wobble. We basically watched three years of a nearly seven-year-long dance of the star and its...

Centauri Dreams has often discussed red dwarf stars and the question of habitability. This time let's focus in on a nearby candidate called AU Mic, an M-class dwarf some 10 parsecs (roughly 32 light years) from Earth. At twelve million years old, this is one of the nearest young dwarfs, and it's known to possess a dusty debris disk. In fact, what we see around AU Mic looks like the late stages of planet formation, with planet-sized objects disturbing smaller disk materials and creating something like our own Kuiper Belt. The lesson of AU Mic seems clear: planet formation around M-class dwarfs is probably common, even though we see few debris disks around older stars of this class. That may simply be the result of the sensitivity of our search technologies, and in any case the smallest exoplanets we've yet found orbiting main sequence stars orbit red dwarfs (consider the rocky world around Gliese 876). Let's be clear on this: we're likely to get solid confirmation of smaller,...

"Hot Jupiters?" read a recent e-mail. "Who cares about hot Jupiters? What I'm after are planets like Earth, rocky terrestrial worlds." My correspondent probably feels the same way today, after NASA's announcement of sixteen new extrasolar planet candidates, all of which fall into the hot Jupiter category and some into an even more bizarre niche -- Ultra-Short-Period Planets, or USPPs. One of these star-hugging worlds, called SWEEPS-10, orbits its parent star once every ten hours. But not so fast. Sure, getting those first terrestrial world detections, presumably through the transit method, is going to be phenomenal, but the steps leading up to that breakthrough are hugely significant. The results announced today didn't involve nearby stars but were focused on 180,000 stars in the Milky Way's central bulge, fully 26,000 light years from Earth. And what can be extrapolated from these sixteen planets is that planet-formation isn't a local phenomenon limited to regions out in the spiral...

We've recently looked at the effects of massive stars on the debris disks surrounding them. Now the Spitzer Space Telescope has shed new light on just how problematic such environments can be. The huge O-type stars studied by a team of scientists from the University of Arizona's Steward Observatory (Tucson) are pouring ultraviolet light and powerful solar winds into the protoplanetary disks around Sun-like stars that have the misfortune of being too near to them. The result: Disruption of the disk through a process called photoevaporation. An O star can be as much as 100 times more massive than the Sun, able to heat a nearby star's disk to the point that gas and dust boil off. With the disk unable to hold together, the evaporated material is eventually blown away by solar winds. The result creates what researchers are calling a 'cometary structure' -- the photoevaporation that causes it is something like what happens when a comet forms its tail in its swing through the inner solar...