for National Geographic News
Astronomers today unvieled unprecedented glimpses of alien planets, including the first ever images of another multiplanet system and the first visible-light images of a planet outside the solar system.
The discoveries represent major advances in our planet-finding abilities and raise hopes for perhaps the ultimate astronomical milestone: the first picture of an Earthlike planet.
Planets outside our solar system—called exoplanets—are usually detected only indirectly, without any kind of visual confirmation of the planets.
Their gravitational fields can induce detectable "wobbles" in their host stars, for example. Or when a planet crosses in front of its star, the planet can "bend" the starlight, tipping off scientists.
Actual imaging of an extrasolar planet, though, is nearly unheard of. (See "First Picture of Alien Planet Orbiting Sunlike Star?" [September 15, 2008]).
"It's something that people have understood for a long time, but this is the first time you can actually see a picture of planets going around a star," NASA researcher Mark Marley said.
"It's like you know that there's somebody in the next room, but now you open the door and you see what they look like," said Marley, who was not involved with either of two exoplanet studies published today on the Web site of the journal Science.
Alien Star System
Earth-based telescopes captured the multiplanet system, which orbits the star HR 8799, in a frame-by-frame movie, according to one of the new studies.
The relatively new infrared technology used by Hawaii's Gemini North telescope and the W.M. Keck Observatory had previously captured a single exoplanet in 2004 (see picture). Infrared light is invisible to the naked eye.
With the new direct-imaging technique, astronomers were able to confirm the planets' presence by observing the system for less an hour total, though over the course of several months, said HR 8799 study leader Christian Marois of Canada's Herzberg Institute of Astrophysics.
By contrast, indirect methods of verifying an exoplanet require many different types of information and sometimes waiting for a suspected planet to make a complete orbit of its star—which in the case of the HR 8799 system would have taken about 450 years.
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