Coming into the picture. An image of 15 Sge and its companion, a brown dwarf. The picture on the right has been processed to show the companion more clearly.

Exoplanet Snapshot Within Reach?

WASHINGTON, D.C.--To capture their first-ever image of an extrasolar planet, some astronomers think they won't need the expensive space-based observatories that are now on the drawing table. Two new observations suggest that existing ground-based telescopes may suffice, thanks to a revolutionary new technique called adaptive optics--in fact, some astronomers believe the first snapshot of an exoplanet may arrive within a year.

Astronomers have deduced the existence of extrasolar planets from the way they tug at their mother stars. Nobody has ever seen one, because they're much too faint compared to their stars. But young planets still glow with the heat of their formation, making them up to 10,000 times brighter than a giant planet like Jupiter would be, says astronomer Ray Jayawardhana of the University of California, Berkeley. That means they may be detected by 10-meter telescopes using adaptive optics, he says, in which a computer wiggles flexible mirrors to compensate for image distortions caused by turbulence in Earth's atmosphere. The technique gives ground-based telescopes the same acuity as the Hubble Space Telescope. And big instruments like the 10-meter Keck telescope and the 8.1-meter Gemini North telescope, both in Hawaii, collect much more light than Hubble's 2.4-meter mirror, making them more sensitive to faint companions.

Using adaptive optics, Jayawardhana, together with Kevin Luhman of the Harvard-Smithsonian Center for Astrophysics in Cambridge, Massachusetts, has detected a dust disk around one member of a newly born quadruple star system that's 900 light-years away. Meanwhile, Michael Liu of the University of Hawaii Institute for Astronomy and his collaborators have found a faint brown dwarf--a "failed star"--orbiting close to a sunlike star called 15 Sge at a distance of 58 light-years. The findings, both presented here yesterday at a meeting of the American Astronomical Society, are evidence of the huge potential of adaptive optics, says Jayawardhana, adding that the race is now on for the first picture of a young planet. In fact, he says he has already detected "a few candidates" that just need a little more work.

"Both discoveries are marvelous, but these are really just tantalizing appetizers for things to come," agrees Alan Boss of the Carnegie Institution of Washington in Washington, D.C. Boss expects the first image of a newly forming planet within a few years, maybe sooner. Although this planet won't be as small as Earth, it would be an important step toward showing that "our solar system is not the fluke in the universe," Boss says.

Related site

An introduction to adaptive optics