|Discovery date 1 April 2005|
Minor planet category Aten NEO, PHA
Discovered 1 April 2005
Discovery site Siding Spring Observatory
Discoverer Siding Spring Survey
|MPC designation (308242) 2005 GO21|
Observation arc 3385 days (9.27 yr)
Absolute magnitude 16.5
Asteroid group Aten asteroid
|Discovered by Siding Spring Survey (E12)
0.5-m Uppsala Schmidt|
Aphelion 1.0093 AU (150.99 Gm) (Q)
Similar 4581 Asclepius, 2012 DR30, 4179 Toutatis
(308242) 2005 GO21 is a large Aten near-Earth asteroid and potentially hazardous object. It has a well determined orbit with an observation arc of 7 years and an uncertainty parameter of 0. It was discovered on 1 April 2005 by the Siding Spring Survey at an apparent magnitude of 18.1 using the 0.5-metre (20 in) Uppsala Southern Schmidt Telescope.
Based on an absolute magnitude of 16.4, the asteroid has an estimated diameter of 1.6 km (within a factor of two). (308242) 2005 GO21 is the largest potentially hazardous asteroid (PHA) discovered in 2005. On 21 June 2012 it passed Earth at a distance of 0.043963 AU (6,576,800 km; 4,086,600 mi). The 2012 passage was studied with radar using Goldstone and Arecibo.