首顆觀測到的小行星(NEO)變成火流星及殞石
On October 6, 2008, Richard Kowalski discovered the now famous asteroid 2008 TC3 at the Catalina Sky Survey in Arizona. Soon thereafter, it became clear that this minor planet would hit the Earth's atmosphere within a few hours time: So this was the first asteroid that was seen in space before it eventually collided with our home planet.this body reached the Earth's surface, a number of small meteorites originating form this asteroid have been recovered in northern Sudan. The strewnfield of the meteorite, which is now known under the name Almahata Sitta
http://en.wikipedia.org/wiki/2008_TC3
The meteoroid was notable as the first such body to be observed and tracked prior to reaching Earth. The process of detecting and tracking a near-Earth object, an effort sometimes referred to as Spaceguard, was put to a test. In total, 586 astrometric and almost as many photometric observations were performed by 27 amateur and professional observers in less than 19.0 hours and reported to the Minor Planet Center, which issued 25 Minor Planet Electronic Circulars with new orbit solutions in eleven hours as observations poured in. On October 7, 01:49 UTC, the meteoroid entered the shadow of the Earth which made further observations impossible. Impact predictions were performed by University of Pisa's CLOMON 2 semi-automatic monitoring system as well as Jet Propulsion Laboratory's Sentry system. Spectral observations that were performed by astronomers at the 4.2-meter William Herschel Telescope at La Palma, Canary Islands are consistent with either a C-type or M-type asteroid.
Explosion
The object is confirmed to have entered Earth's atmosphere as a meteor above northern Sudan at a velocity of 12.8 kilometres per second (29,000 mph). Estimated trajectory has the object coming out of the western sky at an azimuth of 281 degrees, and an altitude angle of 19 degrees to the local horizon.
Meteosat 8 / EUMETSAT IR image of the 2008 TC3 explosion. Copyright 2008 EUMETSATIt exploded tens of kilometers above the ground with the energy of 0.9 to 2.1 kilotons of TNT, causing a large fireball or bolide in the early morning sky. Very few people inhabit the remote area of the Nubian Desert where the explosion took place; The Times, however, reported that the meteoroid's "light was so intense that it lit up the sky like a full moon and an airliner 1,400 km (870 miles) away reported seeing the bright flash." A low-resolution image of the explosion was captured by the weather satellite Meteosat 8. The Meteosat images place the fireball at 21°00′N 32°09′E / 21.00°N 32.15°E / 21.00; 32.15 (2008 TC3 fireball). Infrasound detector arrays in Kenya also detected a sound wave from the direction of the expected impact corresponding to energy of 1.1 to 2.1 kilotons of TNT. Meteoroids of this size hit Earth about two or three times a year.
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