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Small Asteroids Fly Past Earth

Two weeks ago a small space rock called 2008 TC3 made astronomical history as the first asteroid that both impacted the Earth and was also observed telescopically while still out in space and on its collision path with our planet. Since then, three more small near-Earth objects making very close approaches have been picked up by the Mount Lemmon Survey in Arizona, the third just a day ago. They were all observed as they receded back towards the depths of interplanetary space. They are notable as being the three smallest asteroids ever observed, and demonstrate the improving capabilities of Spaceguard surveys.

However, none of these asteroids is really part of the impact hazard. Only much larger objects penetrate far enough into the atmosphere to cause damage at ground level. 2008 TC3 was probably the size of a car before it vaporized and was seen spectacularly exploding above Sudan by one of the METEOSAT weather satellites. The three new objects are each estimated to be around a metre in size, large enough to produce a very bright fireball if they were to impact, but no more than that.

While the observational achievements are very encouraging, astronomers are aware that most such small asteroids are still able to fly past the Earth at such small distances without being noticed. All three recent objects came much closer than the Moon's distance, the nearest substantially closer than man-made geostationary satellites. However, all of them were only spotted after they had passed their point of closest approach. But gradually, the skies are being monitored in greater detail than before.

FOR FURTHER INFORMATION PLEASE CONTACT: Dr David Asher or Mr John McFarland at the Armagh Observatory, College Hill, Armagh, BT61 9DG; Tel.: +44-(0)28-3752-2928; djaat signarm.ac.uk

See also: Objects currently known to be within 45 million kilometres of the Earth

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Last Revised: 2008 October 23rd
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