Asteroid Apophis: Some good news and some bad news

University of Hawaiʻi at Mānoa
Karen Rehbock, (808) 956-6829
Asst to the IFA Dir, Institute for Astronomy
Dr. David Tholen, (808) 956-6930
Astronomer, Institute for Astronomy
Posted: Oct 8, 2009

Dr. David Tholen (photo by Karen Teramura, IfA)
Dr. David Tholen (photo by Karen Teramura, IfA)

University of Hawaiʻi at Mānoa asteroid hunter Dr. David Tholen has some good news and some bad news for us. The good news is that the estimated probability of asteroid Apophis colliding with Earth in 2036 has been reduced from 1 chance in about 45,000 to 1 chance in about 250,000. The bad news is that the improved orbit determination for Apophis has revealed a new impact possibility in 2068.

The new estimates are based on an extensive set of observations obtained at Mauna Kea Observatories and analyzed by Tholen, former UH postdoctoral researcher Dr. Fabrizio Bernardi (now at the University of Pisa, Italy), and current UH graduate students Marco Micheli and Garrett Elliott. Dr. Steve Chesley of the Jet Propulsion Laboratory in California determined the positions of Apophis derived from those observations.

“Our new orbit solution shows that Apophis will miss Earth’s surface in 2036 by a scant 20,270 miles, give or take 125 miles,” Tholen said. “That's slightly closer to Earth than most of our communications and weather satellites.” He credits the large telescopes and superb atmospheric conditions on Mauna Kea for being able to make these determinations.

With the possibility of an impact in 2068, Apophis will become the target of even more observations as soon as it reappears from behind the Sun in 2010 and beyond.

Apophis was discovered in 2004 by Tholen, Bernardi, and Roy Tucker of the University of Arizona. The asteroid became famous about six months later when additional observations indicated an impact probability as high as 1 chance in 37 on April 13, 2029 (coincidentally, a Friday). But prediscovery observations identified in data taken earlier in that year soon showed that the asteroid would miss Earth in 2029.

The improved orbit determination is being presented this week at the annual meeting of the Division for Planetary Sciences of the American Astronomical Society being held in Puerto Rico.

Jet Propulsion Laboratory news release:

 Founded in 1967, the Institute for Astronomy at the University of Hawaiʻi at Mānoa conducts research into galaxies, cosmology, stars, planets, and the sun. Its faculty and staff are also involved in astronomy education, deep space missions, and in the development and management of the observatories on Haleakala and Mauna Kea.


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