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  • A Pre-20-Year Anniversary for Asteroid Apophis

    Posted on April 13th, 2009 Dr. Mario M. Bisi No comments


    On 13th April 2029, twenty years from today, the asteroid designated Apophis (full designation 99942 Apophis, originally designated 2004 MN4) is going to come very close to the Earth. It originally caused a brief period of concern throughout December 2004 because some initial observations of its trajectory indicated a significant probability that it would strike the Earth some time in 2029; this probability being up to 2.7%. It was discovered by Roy A. Tucker, David J. Tholen, and Fabrizio Bernardi on 19th June 2004 (hence the orginal 2004 designation).

    Asteroid 951 Gaspra - a much larger asteroid than Apophis - Gaspra was the first ever asteroid to be closely approached by a spacecraft, the Galileo spacecraft, which flew passed on its way to Jupiter on 29th October 29 1991 and luckily poses no threat to the Earth.

    It will fly by at only 18,300 miles above the Earth’s surface. At this relatively-low altitude, it will appear well inside the height of Earth’s manmade geosynchronous communications satellites. At its closest approach, the asteroid (with a width of 300 metres) will shine as bright as a 3rd magnitude star and make itself easily visible to the naked eye from cities across three continents: Europe, Asia, and Africa. After certain calculations, it turns out that there is a small chance (about 1 in 45,000 that is) that the encounter with Apophis in 2029 will bend its orbit sufficiently, so that when it returns to Earth it actually hits it on 13th April 2036 (or so the experts say). Should such an impact arrise, NASA estimates that it could hit the Earth with the equivalent energy of an 880 Megaton bomb! Just as a point of comparison, the 1883 super eruption of the volcano Krakatoa was the equivalent of approximately 200 megatons.

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