2004 FH

2004 FH is a micro-asteroid and near-Earth object of the Aten group, approximately 30 meters in diameter, that passed just 43,000 km above the Earth's surface on 18 March 2004, at 22:08 UTC. It was the 11th closest approach to Earth recorded. The asteroid was first observed on 16 March 2004, by astronomers of the Lincoln Near-Earth Asteroid Research at the Lincoln Laboratory's Experimental Test Site near Socorro, New Mexico.

Orbit and classification


is an Aten asteroid. It passed 43,000 km from the Earth on 18 March 2004. For comparison, geostationary satellites orbit Earth at 35,790 kilometers. Despite its small size, it is still the fourth largest asteroid detected coming closer to the Earth than the Moon.

Had this object hit Earth, it would probably have detonated high in the atmosphere. It might have produced a blast measured in hundreds of kilotons of TNT, but may not have produced any effect on the ground. It could also have been an Earth-grazing fireball if it had been much closer but not close enough to impact.

On 17 March 2044 the asteroid will pass no closer than 0.0116 AU from the Earth. also has the distinction of having the lowest inclination of any known near-Earth asteroids.

Two weeks later another asteroid approached even closer,, which was smaller, and a few years later , which was closer in size passed by at similar distance.

Physical characteristics
is an assumed stony S-type asteroid.

Rotation period
In March 2004, two rotational lightcurves of were obtained from photometric observations by astronomers Petr Pravec, Stefano Sposetti and Raoul Behrend. Lightcurve analysis gave a rotation period of 0.0504 hours (3.02 minutes) with a brightness amplitude of 1.16 and 0.75 magnitude, respectively (U=3/2+).

This makes this object a fast rotator, currently among the Top 100 known to exist. The photometric observations also revealed, that is a tumbler with a non-principal axis rotation.

Diameter and albedo
has been estimated to measure approximately 30 meters (100 feet) in diameter. The Collaborative Asteroid Lightcurve Link assumes a standard albedo for stony asteroids of 0.20 and calculates a diameter of 24 meters based on an absolute magnitude of 25.7.