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Asteroid probably won't hit in 2036, astronomer says


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POSTED: Sunday, October 11, 2009

Asteroid Apophis will skirt the Earth in 2036, but isn't likely to crash into the planet, says the University of Hawaii astronomer who discovered it.

David Tholen, with the Institute for Astronomy, detected the asteroid in 2004 with colleagues Fabrizio Bernardi, a former UH postdoctoral researcher now at the University of Pisa, Italy, and Roy Tucker of the University of Arizona.

“;Our new orbit solution shows that Apophis will miss the Earth's surface in 2036 by a scant 20,270 miles, give or take 125 miles,”; Tholen said in an institute news release. “;That's slightly closer to Earth than most of our communications and weather satellites.”;

Alarm followed the asteroid's discovery when observations indicated a 2.7 percent chance it would strike the Earth on April 13 (a Friday) in 2029.

Later measurements showed the asteroid “;will make a historically close approach to the Earth”; that year, but there is no impact risk, NASA's Near Earth Object Program reported.

Radar observations in 2006 suggested a one in about 45,000 chance of an Apophis-Earth collision in 2036.

Working with extensive new data, Tholen reduced the odds of an impact at that time to one in about 250,000 although his new orbit calculations indicate a collision may occur in 2068.

In an e-mail from Puerto Rico, where he presented his new impact estimates at an American Astronomical Society meeting, Tholen said most of the new data was collected from the UH 88-inch telescope on Mauna Kea, and some from the Subaru telescope.

Apophis moved too close to the sun for additional observations in early 2008 and was last seen on Jan. 9 of that year, he said. “;We might be able to glimpse it with Keck (telescope) next May. Apophis comes our way about every eight years, but the motion is rather complex.”;

He said the Pan-STARRS prototype telescope atop Haleakala, Maui, forerunner for an array of four telescopes to track potentially dangerous near-Earth asteroids, has detected asteroids, “;even some new ones, and a known near-Earth asteroid.”;

The impact prediction software system was tested last year on an asteroid that hit northern Africa and was 100 percent accurate, Tholen said at the time.

However, he said Pan-STARRS isn't in a routine observing mode yet.