Science and Health

US astronomers hunt for nearby stars

(Xinhua)
Updated: 2011-04-08 08:34

LOS ANGELES - Using NASA's Galaxy Evolution Explorer (GEE) satellite, US astronomers are hunting for nearby, hard-to-see stars which could very well be home to the easiest-to-see alien planets, it was announced on Thursday.

US astronomers are ferreting out the new targets after the glare of bright, shining stars has frustrated most efforts at visualizing distant worlds, NASA's Jet Propulsion Laboratory (JPL) said.

So far, only a handful of distant planets, or exoplanets, have been directly imaged. Small, newborn stars are less blinding, making the planets easier to see, but the fact that these stars are dim means they are hard to find in the first place.

"Fortunately, the young stars emit more ultraviolet light than their older counterparts, which makes them conspicuous to the ultraviolet-detecting GEE," JPL said in a press release.

"We've discovered a new technique of using ultraviolet light to search for young, low-mass stars near the Earth," said David Rodriguez, a graduate student of astronomy at University of Californian, Los Angeles. "These young stars make excellent targets for future direct imaging of exoplanets."

Young stars, like human children, tend to be a bit unruly - they spout a greater proportion of energetic X-rays and ultraviolet light than more mature stars. In some cases, X-ray surveys can pick out these youngsters due to the "racket" they cause. However, many smaller, less "noisy" baby stars perfect for exoplanet imaging studies have gone undetected except in the most detailed X-ray surveys. To date, such surveys have covered only a small percentage of the sky, according to JPL in Pasadena, Los Angeles.

Rodriguez and his team figured that the GEE, which has scanned about three-quarters of the sky in ultraviolet light, could fill this gap.

Astronomers compared readings from the telescope with optical and infrared data to look for the telltale signature of rambunctious junior stars. Follow-up observations of 24 candidates identified in this manner determined that 17 of the stars showed clear signs of youth, validating the team's approach, JPL said.

"The Galaxy Evolution Explorer can readily select young, low- mass stars that are too faint to turn up in all-sky X-ray surveys, which makes the telescope an incredibly useful tool," Rodriguez said in the release.