Seeing a planet around another star means finding a way to mask the overwhelming glare that swamps the faint image. The job is, as a news release from the American Institute of Physics reminds us, something like trying to see the light of a match held next to an automobile's headlight from a distance of 100 meters. Consider that the Earth is ten billion times less bright than the Sun at optical wavelengths and you see the enormity of the problem. Among the possible solutions is an approach taken by Grover Swartzlander and his colleagues at the University of Arizona. Swartzlander eliminates excessive starlight by feeding it through a helical 'mask' -- a kind of lens. The result is what the team calls an optical vortex coronagraph. From the news release: The process works in the following way: light passing through the thicker and central part of the mask is slowed down. Because of the graduated shape of the glass, an "optical vortex" is created: the light coming along the axis of the...

The search for planets around small stars seems to be gaining in intensity. Now a team of French and Swiss astronomers has announced the discovery of a Neptune-class planet around the star Gliese 581. The Gliese catalog lists all known stars within 25 parsecs (81.5 light years) of the Sun, making its listings of significant interest in the hunt for exoplanets and, long-term, in our thinking about robotic interstellar probes. Also catching the eye is the fact that this star is a red dwarf, confirming the notion that such stars are ripe for exoplanetary investigation. Gliese 581 is 20.5 light years away in the constellation Libra. Red dwarfs like it make up about 70 percent of the galactic population; in fact, of the 100 stars closest to the Sun, fully 80 are red dwarfs. Earlier surveys of red dwarfs have revealed few with planets, but Stéphane Udry (Geneva Observatory), a co-author of the paper on the new find, believes the earlier surveys may have operated with insufficient...

As if we didn't already have enough trouble defining what a planet is, astronomers have now discovered a brown dwarf only eight times the mass of Jupiter. Surrounded by a dusty disk, the object is actually smaller than a number of planets already known to be orbiting other stars. Any miniature solar system that formed around the brown dwarf would be roughly 100 times smaller than our own. All of which raises the question of what to call objects that might be found around this tiny dwarf: planets or moons? The question has obvious resonance in an era marked by repeated discoveries in the Kuiper Belt that could be considered of planetary size. And another sign of the ambiguity in definition is that worlds like Titan, Ganymede and Callisto are large enough in their own right to qualify as planets, if we overlook the inconvenient fact that they orbit massive planets of their own. The question may seem insignificant, but how we define things is ultimately a measure of how extensive our...

M-class red dwarfs have never figured prominently in the SETI search. The reason for this is apparent: such stars, of which Proxima Centauri, Earth's nearest stellar neighbor, is one, are flare stars. The intense radiation from solar flares should cleanse a planetary surface of life, especially given the close proximity of such a planet to its star. Remember, the habitable zone around a red dwarf is going to occur well inside the orbit of Mercury. And there's a second reason. By virtue of having to orbit the host star so tightly, a planet around a red dwarf is going to be tidally locked. One side would be baked, the other frozen, which makes the odds on liquid water look slim. But assumptions are made to be questioned, which is why work at Ames Research Center in the late 1990s remains so interesting. One implication of the Ames work, for example, is that there are conceivable weather patterns that could circulate heat to the dark side of a tidally locked world, keeping it warm...

If you're going to have a conference on exoplanets, there is no better venue than l'Observatoire de Haute-Provence. It was here, just ten years ago, that Mayor and Queloz discovered the first planet orbiting a main sequence star outside our own Solar System. The star was 51 Pegasi, a name that will surely be recalled for generations as the first confirmation that planets exist around other stars. And attendees at a late August conference celebrating the discovery had much to say about the course of future exoplanetary developments. David Charbonneau (Harvard-Smithsonian Center for Astrophysics) summarizes the conference findings in his paper "Hot Jupiters: Lands of Plenty," now available on the arXiv site. A major issue stands out: the huge leap in precision for radial velocity observations of the sort that bagged 51 Pegasi's planet, allowing researchers to monitor a wider group of stars than the F, G, K and early M-class dwarfs that have been the focus heretofore. The new precision...