potentially hazardous asteroid
McGraw-Hill Science & Technology Dictionary:
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potentially hazardous asteroid
(pə′ten·chə·lē ′haz·ərd·əs ′as·tə′röid)
(astronomy) An asteroid whose orbit approaches within 0.05 astronomical unit of the earth's orbit, and which is brighter than an absolute visual magnitude of 22.0, corresponding to a diameter of at least 110-240 meters (360-800 feet).
Wiley Book of Astronomy:
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potentially hazardous asteroid
A near-Earth asteroid (NEA) whose orbit can bring it so close to Earth that there is a risk (typically very small) of a future collision. Past asteroid and comet impacts have had dramatic effects both on a local scale (as in the case of the Tunguska event) and globally (for example, the mass extinction at the K-T boundary). The growing realization that Earth will inevitably be hit hard again at some point, with potentially catastrophic results for human and other life, has led to the setting up of several programs to detect and monitor NEAs (or, more generally, NEOs—near-Earth objects—which also include short-period comets) and near-Earth threatening objects. These include the Spacewatch Program, LINEAR, the Space-guard Foundation, and the Jet Propulsion Laboratory's NEO Program. Among recent close encounters was one on June 14, 2002, when an asteroid the size of a football pitch, cataloged as 2002 MN, passed Earth at a distance of around 120,000 km—less than a third the distance to the Moon—traveling at over 10 km/s (23,000 miles per hour). This was bettered by 1994XM1, which came to within 105,000 km of Earth in December 1994.
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McGraw-Hill Science & Technology Dictionary
McGraw-Hill Dictionary of Scientific and Technical Terms. Copyright © 2003, 1994, 1989, 1984, 1978, 1976, 1974 by McGraw-Hill Companies, Inc. All rights reserved.
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