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NASA refines asteroid's path toward Earth
Posted: October 08, 2009

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Using updated information, NASA scientists have recalculated the path of the large asteroid Apophis that significantly reduces its chances of striking Earth in 2036.

The doomsday asteroid is around 350 metres wide and first made the headlines in December 2004 when initial observations predicted a 2.7 percent chance of impacting the Earth in 2029.

Asteroid Apophis was discovered on June 19, 2004. Image: UH/IA

“Apophis has been one of those celestial bodies that has captured the public’s interest since it was discovered in 2004,” says Steve Chesley of NASA’s Jet Propulsion Laboratory. “Updated computational techniques and newly available data indicate the probability of an Earth encounter on April 13, 2036, for Apophis has dropped from one-in-45,000 to about four-in-a million.”

Collaborators at the University of Hawaii’s Institute for Astronomy in Manoa worked on hundreds of previously unreleased images derived from the University of Hawaii’s 88-inch telescope, the Steward Observatory’s 90-inch Bok telescope on Kitt Peak in Arizona and the Arecibo Observatory on the island of Puerto Rico to improve measurements of the asteroid's position. Although Earth may be off the hook for an impact in 2029, the revised orbit predicts a close encounter in 2068 with a chance of impact currently at three in a million. But as with the 2029 and 2036 predictions, the chance of impact in 2068 will likely diminish once more information is gathered.

Does Apophis have Earth in its sights for 2068 instead? AN graphic by Greg Smye-Rumsby.

Apophis is still expected to make a record close approach to Earth on Friday 13 April 2029, however, when it will pass within 29,500 kilometres. “The refined orbital determination further reinforces that Apophis is an asteroid we can look to as an opportunity for exciting science and not something that should be feared,” says Don Yeomans, manager of the Near-Earth Object Program Office at JPL. “The public can follow along as we continue to study Apophis and other near-Earth objects by visiting us on our AsteroidWatch Web site and by following us on the @AsteroidWatch Twitter feed.”

NASA is dedicated to detecting and tracking asteroids and comets that may pose a threat to the Earth as part of the Near-Earth Object Observations Program, otherwise known as Spaceguard. The objects' properties are characterised and their orbital parameters predicted based on observations and standard models of the gravitational influences within the Solar System.