Close-Call Asteroid Coming


Astronomers admitted this week that there is a small but real possibility that an asteroid could hit the Earth in less than 50 years. The asteroid of the hour — designated 1999 AN10 — had been put on the list of "potentially hazardous objects" soon after its discovery earlier this year. A team of Italian astronomers determined that there was a one-in-a-billion chance of impact in 2039 and their results were prematurely announced by outside individuals. While the object became a topic of discussion in astronomical circles, it didn’t cause a widespread media frenzy as with minor planet 1997 XF11 a year ago. Once the object cleared the Sun and could be observed again, additional positions and analysis eliminated the 2039 threat, but revealed that 1999 AN10 would skirt the Earth on August 7, 2027, perhaps as close as 30,000 kilometers above Earth’s surface. The situation changed with yet more positions of the object, and on May 26th, Paul W. Chodas (Jet Propulsion Laboratory) announced that analysis by several dynamicists revealed that while the asteroid could not hit us on 2027, the uncertainty of where the object would be when it came by the planet allowed "keyholes" that could send it on a collision course in 2044 or 2046. The odds of a collision are now roughly one in 500,000 — slightly more likely than a chance hit from an undiscovered asteroid over the next 40 years. Further observations of 1999 AN10 will help refine its orbit and shrink the error ellipse. Thus even this danger could evaporate.

Copyright 1999 Sky Publishing Corporation. S&T’s Weekly News Bulletin and Sky at a Glance stargazing calendar are provided as a service to the astronomical community by the editors of SKY & TELESCOPE magazine. Widespread electronic distribution is encouraged as long as these paragraphs are included. But the text of the bulletin and calendar may not be published in any other form without permission from Sky Publishing (contact or phone 617-864-7360). Updates of astronomical news, including active links to related Internet resources, are available via SKY & TELESCOPE’s site on the World Wide Web at

via Close-Call Asteroid Coming.


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