Image of the Month - April 2004

Closest Flyby ever

Asteroid 2004 FH, discovered by the LINEAR asteroid survey on 2004 March 16, passed about 43,000km above the surface of the south Atlantic Ocean less than three days later. This is the closest approach of an asteroid ever recorded by mankind, sending 2003 SQ₂₂₂, which approaced the Earth to about 84'000km only half a year earlier, off to second place. The flyby-distance of 2004 FH corresponds to only 13% of the mean distance between the Earth and the Moon, or about eight times the Earth's radius. It is also just about one third more distand than the many man-made satellites that inhabit the geostationary ring.

Credit & Copyright: Stefano Sposetti, Gnosca Observatory, Switzerland

Swiss astrophotographer Stefano Sposetti captured the small space rock, estimated to be only 30 meters in diameter, on March 18, when it was still 560'000km from Earth (about 1,5 times the Earth-Moon distance). A total of 61 images, each a 15 second exposure taken with the 0.4m Newtonian reflector in Sposetti's private observatory, have been added to create this view. Besides the motion of the asteroid, the image clearly shows variations in the brightness of the object, caused by the fast rotation of this minor planet. The three bright trails at the bottom of these images were left by an artificial satellite that crossed the scene. Raoul Behrend from the Geneva Observatory also constructed a beautiful animation from these images.

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