2008 HJ

2008 HJ is a sub-kilometer asteroid, classified as near-Earth object of the Apollo group.

2008 HJ

Discovery
Discovered by	LINEAR
Discovery site	Lincoln Lab ETS
Discovery date	24 April 2008
Designations
MPC designation	2008 HJ
Minor planet category	NEO · Apollo[1]
Orbital characteristics[1]
Epoch 13 January 2016 (JD 2457400.5)
Uncertainty parameter 6
Aphelion	2.29553 AU (343.406 Gm) (Q)
Perihelion	0.968318 AU (144.8583 Gm) (q)
Semi-major axis	1.63192 AU (244.132 Gm) (a)
Eccentricity	0.40664 (e)
Orbital period (sidereal)	2.08 yr (761.46 d)
Mean anomaly	237.912° (M)
Mean motion	0° 28m 21.99s /day (n)
Inclination	0.925579° (i)
Longitude of ascending node	47.4700° (Ω)
Argument of perihelion	204.1346° (ω)
Earth MOID	0.00170917 AU (255,688 km)
Jupiter MOID	2.75111 AU (411.560 Gm)
Physical characteristics
Dimensions	12×24 m
Mass	5 million kg (assumed)
Sidereal rotation period	42.7 s (0.01185 h)
Absolute magnitude (H)	25.8[1]

It was discovered by Lincoln Laboratory ETS, New Mexico. Observers M. Bezpalko, D. Torres, R. Kracke, G. Spitz, J. Kistler. Richard Miles using the Faulkes Telescope South at Siding Spring Observatory, Australia determined that the asteroid rotates rapidly. It measures only 12 m by 24 m and is very dense, having a mass of about 5,000 tonnes. If the asteroid were not dense, it is probable that the rapid rotation would cause the asteroid to disrupt and fly apart.

At the time of discovery, 2008 HJ had the smallest known rotation period in the Solar System, completing one revolution every 42.7 seconds.^[1][2]

It is listed on the Sentry Risk Table with a 1 in 17,000 chance of impacting Earth on May 2, 2081.^[3] An impact from this object would be comparable to the Chelyabinsk meteor.

See also

• List of fast rotators (minor planets)