Are pictures of extrasolar planets in the offing? (Astronomy).
Because stars are thousands to billions of times brighter than their planets, even a planet several times as massive as Jupiter is not easy to discern against the glare of its stellar parent. That's why researchers have so far inferred the existence of the 80 or so known extrasolar planets only indirectly, by the wobble they induce in the motion of the stars they orbit.
Adaptive optics now promises to provide the first direct visual evidence of extrasolar planets. The technique relies on a computer-controlled system that subtly reshapes a telescope's mirror hundreds of times a second to compensate for the blurring caused by Earth's turbulent atmosphere (SN: 3/4/00, p. 156). Over the past few years, astronomers have installed such systems on some of the world's largest telescopes, including the 10-meter Keck II and the 8.1-m Gemini North on Mauna Kea in Hawaii.
The extraordinary resolution afforded by the technology can clearly separate a young planet from its parent star, say Ray Jaywardhana of the University of California, Berkeley and Michael Liu of the University of Hawaii in Honolulu. Researchers don't yet have an image of a bona fide extrasolar planet--or if they do, they're not ready to unveil it. But Liu and Jaywardhana proudly displayed pictures that provide a taste of what's to come.
At both Keck II and Gemini North, Liu and his colleagues took images of a failed star, or brown dwarf, orbiting a young, sun-like star at a distance that could be just slightly greater than that at which Saturn orbits our sun. Depending on the exact orientation of the brown dwarf, the separation between it and the star it orbits could be the smallest of any brown dwarf ever imaged. The star, which resides in the constellation Sagitta, lies 58 light-years from Earth.
A team led by Jaywardhana used the adaptive optics system on Gemini North to examine what appeared to be two widely spaced stars that orbit each other. The images reveal that one of these stars is actually two pairs of stars. Moreover, in this quadruple system, the researchers spied a dusty disk--a possible planetary system in the making. It's the first protoplanetary disk ever found around a four-star system.
The images are graphic proof that astronomers are on the verge of photographing newly formed planets, says Alan P. Boss of the Carnegie Institution of Washington (D.C.). Combining adaptive optics with coronagraphs, devices that blot out the bright light of a parent star, will further hasten the discovery, Jaywardhana adds.--R.C.
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|Article Type:||Brief Article|
|Date:||Jan 26, 2002|
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