2004 FH is a micro- asteroid and

near-Earth object A near-Earth object (NEO) is any small Solar System body whose orbit brings it into proximity with Earth. By convention, a Solar System body is a NEO if its closest approach to the Sun (perihelion) is less than 1.3 astronomical units (AU). ...

of the Aten group, approximately 30 meters in diameter, that passed just above the

Earth Earth is the third planet from the Sun and the only astronomical object known to harbor life. While large volumes of water can be found throughout the Solar System, only Earth sustains liquid surface water. About 71% of Earth's surfa ...

'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 The Lincoln Near-Earth Asteroid Research (LINEAR) project is a collaboration of the United States Air Force, NASA, and the Massachusetts Institute of Technology's Lincoln Laboratory for the systematic detection and tracking of near-Earth objects ...

at the Lincoln Laboratory's Experimental Test Site near Socorro, New Mexico.

Orbit and classification

is an

Aten asteroid The Aten asteroids are a dynamical group of asteroids whose orbits bring them into proximity with Earth. By definition, Atens are Earth-crossing asteroids . The group is named after 2062 Aten, the first of its kind, discovered on 7 January ...

. It passed 43,000 km from the Earth on 18 March 2004. For comparison,

geostationary satellite A geostationary orbit, also referred to as a geosynchronous equatorial orbit''Geostationary orbit'' and ''Geosynchronous (equatorial) orbit'' are used somewhat interchangeably in sources. (GEO), is a circular geosynchronous orbit in altitude ...

s 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 Trinitrotoluene (), more commonly known as TNT, more specifically 2,4,6-trinitrotoluene, and by its preferred IUPAC name 2-methyl-1,3,5-trinitrobenzene, is a chemical compound with the formula C6H2(NO2)3CH3. TNT is occasionally used as a reagen ...

, but may not have produced any effect on the ground. It could also have been an

Earth-grazing fireball An Earth-grazing fireball (or Earth grazer) is a fireball, a very bright meteor that enters Earth’s atmosphere and leaves again. Some fragments may impact Earth as meteorites, if the meteor starts to break up or explodes in mid-air. These phenom ...

if it had been much closer but not close enough to impact. On 17 March 2044 the asteroid will pass no closer than from the Earth. also has the distinction of having the lowest

inclination Orbital inclination measures the tilt of an object's orbit around a celestial body. It is expressed as the angle between a reference plane and the orbital plane or axis of direction of the orbiting object. For a satellite orbiting the Eart ...

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 S-type asteroids are asteroids with a spectral type that is indicative of a siliceous (i.e. stony) mineralogical composition, hence the name. They have relatively high density. Approximately 17% of asteroids are of this type, making it the secon ...

Rotation period

In March 2004, two rotational

lightcurve In astronomy, a light curve is a graph of light intensity of a celestial object or region as a function of time, typically with the magnitude of light received on the y axis and with time on the x axis. The light is usually in a particular freq ...

s of were obtained from photometric observations by astronomers

Petr Pravec Petr Pravec (born September 17, 1967) is a Czech astronomer and a discoverer of minor planets, born in Třinec, Czech Republic. Pravec is a prolific discoverer of binary asteroids, expert in photometric observations and rotational lightcurves ...

Stefano Sposetti Stefano Sposetti (born 22 December 1958) is a Swiss amateur astronomer and a prolific discoverer of minor planets. He lives in Gnosca, in the Italian-speaking part of Switzerland in the Ticino Alps, where the Gnosca Observatory is located. Spo ...

and

Raoul Behrend This is a list of minor-planet discoverers credited by the Minor Planet Center with the discovery of one or several minor planets (such as near-Earth and main-belt asteroids, Jupiter trojans and distant objects). , the discovery of 612,011 num ...

. Lightcurve analysis gave a rotation period of 0.0504 hours (3.02 minutes) with a brightness amplitude of 1.16 and 0.75

magnitude Magnitude may refer to: Mathematics *Euclidean vector, a quantity defined by both its magnitude and its direction *Magnitude (mathematics), the relative size of an object *Norm (mathematics), a term for the size or length of a vector *Order of ...

, respectively (). 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 Albedo (; ) is the measure of the diffuse reflection of solar radiation out of the total solar radiation and measured on a scale from 0, corresponding to a black body that absorbs all incident radiation, to 1, corresponding to a body that refl ...

for stony asteroids of 0.20 and calculates a diameter of 24 meters based on an

absolute magnitude Absolute magnitude () is a measure of the luminosity of a celestial object on an inverse logarithmic astronomical magnitude scale. An object's absolute magnitude is defined to be equal to the apparent magnitude that the object would have if it ...

of 25.7.

Notes

References

External links

MPEC 2004-F24

at Klet
Asteroid Lightcurve Database (LCDB)
query form

)

– Observatoire de Genève, Raoul Behrend * * * {{DEFAULTSORT:2004 FH # Minor planet object articles (unnumbered) # 20040318 20040316