The Hubble Space Telescope cost far more to build and launch than the twin telescopes of Hawaii's W.M. Keck Observatory, but Keck gathers twenty times the light and offers four to five times better resolution. Assuming, of course, that we can find a way to cancel out the effects of atmospheric blurring on its images. That's where the science of adaptive optics comes in. By using a bright reference beacon nearby, an observatory like Keck can analyze atmospheric effects even as its observations are being made. That this technique can be used in the hunt for extrasolar planets is clear. The infrared image to the right (credit: Michael Liu, IFA-Hawaii/W. M. Keck Observatory) shows a dust disk surrounding the star AU Microscopii. The image is 100 AU wide, roughly the size of our Solar System; Keck's images are the sharpest ever obtained of a circumstellar disk, with an angular resolution of 1/25 of an arcsecond, about 1/500,000 the diameter of the full moon. But adaptive optics has a...

At 12 light years away, Tau Ceti is the nearest Sun-like star, and has long been of high biological interest among possible interstellar probe targets. But a British team using the James Clerk Maxwell Telescope in Hawaii (and aided by the world's most sensitive sub-millimeter camera, called SCUBA) has found a disk of cold dust around the star that bodes ill for stability among any planets that may be orbiting there. Says Jane Greaves, lead scientist on the study: "Tau Ceti has more than ten times the number of comets and asteroids that there are in our Solar System. We don't yet know whether there are any planets orbiting Tau Ceti, but if there are, it is likely that they will experience constant bombardment from asteroids of the kind that is believed to have wiped out the dinosaurs. It is likely that with so many large impacts life would not have the opportunity to evolve." Image: Bombardment of a hypothetical planet around Tau Ceti: bad news for life? Credit: David Hardy. Frank...

A network of robotic telescopes called RoboNet-1.0 will soon join the hunt for Earth-like planets around other stars. RoboNet will look for the effects of gravitational micro-lensing, where distant light is bent around an unseen foreground object. A star whose light is undergoing such lensing would, if it had a planet, show a blip in its detected light which RoboNet should be able to follow-up. "The network," says a press release from the Particle Physics and Astronomy Research Council, which funded the project, "stands the best chance of any existing facility of actually finding another Earth due to the large size of the telescopes, their excellent sites and sensitive instrumentation." The globally distributed RoboNet offers astronomers the chance to search anywhere in the sky without regard to local light conditions by passing observations from one telescope to the next. The Liverpool Telescope (Canary Islands), Faulkes North (Maui) and Faulkes South (New South Wales) telescopes...

An interesting piece in Nature's online edition describes the race to see who has actually imaged a planet around another star. As discussed in Centauri Dreams earlier, a team in Chile at the European Southern Observatory has used infrared to reveal what may be a planet circling the star 2M1207, a brown dwarf, but there is still no conclusive evidence that the planetary candidate actually orbits the star. But another team, from Pennsylvania State University and using Hubble images, also believes it has found such an object, though they won't yet name the star or discuss its location for fear of being scooped. If the PSU object is indeed a planet, it is between five and ten times the mass of Jupiter and roughly 100 light years from Earth, in an orbit similar to that of Neptune around our Sun. Infrared is useful in both sets of observations because the contrast between a star and its planet is a thousand times less at these wavelengths; in visual light, the glow of a planet is...

Getting an image of a planet around another star has been an elusive goal for astronomers, and most candidates have proven to be background stars, or sometimes faint stellar members of what turned out to be binary systems. Now a new candidate has emerged. An international team of astronmers, using observations from the the ESO Paranal Observatory in northern Chile, has picked up what may be a gas giant planet orbiting the brown dwarf 2M1207 at approximately twice the distance between the Sun and Neptune. The object is located in the far southern sky in the direction of the constellation Hydra, and is approximately 230 light years away. The photograph at left is based on three near-infrared exposures (in the H, K and L' wavebands) with the NACO adaptive-optics facility at the 8.2-m VLT Yepun telescope at the ESO Paranal Observatory. More observations are needed, but what's interesting about this 'Giant Planet Candidate Companion,' as it is being called, is that its spectrum shows...