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Infrared eye to help search for asteroids

NASA is preparing to launch an infrared telescope named WISE that could indeed live up to its name.
/ Source: Discovery Channel

NASA is preparing to launch an infrared telescope named WISE that could indeed live up to its name. Among its targets: dark asteroids that have slipped beneath the radar of an ongoing project to map objects larger than 1 kilometer that orbit near Earth.

Hunting asteroids wasn't in the original plan for the Wide-field Infrared Survey Explorer, known by the acronym WISE, which arrived at Vandenberg Air Force Base in California this month for launch preparations.

"I was recruited when the team realized they would be seeing a lot of asteroids, some of which may be new," said University of Texas astronomer Robert McMillan who leads Spacewatch, an asteroid-survey project.

"They wanted someone who had connections with the ground-based telescope community who'd be able to do follow-ups," McMillan told Discovery News.

With a quartet of infrared sensors and a wide view, WISE is designed to survey the whole sky in infrared light. It's not the first telescope to do so, but scientists expect WISE's observations will be 500 times sharper than a survey conducted in 1980s by IRAS, the Infrared Astronomical Satellite, said astronomer Martin Cohen, with the University of California at Berkeley.

The data will be complied into an all-sky infrared atlas, a tome that is expected to include about 300 million objects, including about 100,000 asteroids.

Many of the asteroids seen by WISE will be known objects. Scientists hope to use the new observations to nail down details, such as an asteroid's diameter and surface reflectivity.

"With ground-based scopes, it's just a point source. You can't tell size directly," McMillan said. "A big object that is dark and a small object that is bright are going to look like they have the same brightness."

The solar system contains several million asteroids, most of which reside in the Main Asteroid Belt between Mars and Jupiter. About 7,000 asteroids have been identified that cross or come close to Earth's orbit.

WISE will be able to spot asteroids emitting heat due to direct exposure from the sun, as opposed to visible-light searches that find asteroids that are reflecting sunlight.

"Those are two different physical effects," said McMillan. "An asteroid that has very dark color in invisible light is going to get heated up more, just like a black car in a parking lot is going to get heated up more than a white car."

Scientists hope to get enough positioning information to follow up targets with ground-based observations. McMillan expects that WISE will discover a few hundred new asteroids. The information will be folded into ongoing surveys to map asteroids that could impact Earth and cause widespread damage.

Other WISE targets include brown dwarfs, which are Jupiter-sized stars that never got their nuclear fusion engines running and ultra-luminous galaxies, which pump out the equivalent of about 1,000 sun-sized stars every year.

These galaxies are among the most luminous objects in universe, said WISE lead scientist Edward Wright.

WISE should be able to spot these galaxies back to when the universe was about 2 billion years old.

The telescope is scheduled to be launched on Dec. 7. The $300 million mission covers a month-long checkout and six months of science operations. The spacecraft is designed to last two years.