Below is the list of asteroid close approaches to Earth in 2008. 2008 was the first year that an asteroid was successfully detected before it impacted earth (2008 TC3 was the first successfully predicted asteroid impact).
Timeline of close approaches less than one lunar distance from Earth in 2008
Rows highlighted red indicate objects which were not discovered until after closest approach
Rows highlighted yellow indicate objects discovered less than 24 hours before closest approach
Rows highlighted green indicate objects discovered more than one week before closest approach
Rows highlighted turquoise indicate objects discovered more than 7 weeks before closest approach
Rows highlighted blue indicate objects discovered more than one year before closest approach (i.e. objects successfully cataloged on a previous orbit, rather than being detected during final approach)
Apart from 2008 TC3, this list does not include any of the other objects that collided with earth in 2008 as they were not discovered in advance, but were recorded by sensors designed to detect detonation of nuclear devices.[note 2]
This table visualizes the warning times of the close approaches listed in the above table, depending on the size of the asteroid. The sizes of each pie chart show the relative sizes of the asteroids to scale. For comparison, the approximate size of a person is also shown. This is based around the absolute magnitude of each asteroid, an approximate measure of size based on brightness.
^Asteroids which collide with earth before being detected never receive a designation and do not appear in either the NASA or IAU lists of asteroids as there is no astrometry for them.
^Distance from the center of Earth to the center of the object. See the NASA/JPL Solar System Dynamics Glossary: Geocentric. Earth has a radius of approximately 6,400 km.
Additional examples
An example list of near-Earth asteroids that passed more than 1 lunar distance (384,400 km or 0.00256 AU) from Earth in 2008.
2007 TU24 (~250 meters in diameter) passed 1.44 LD (554,000 km) from Earth on January 29, 2008.
2008 CE22 (~18 meters in diameter) passed between 0.9997 and 1.0023 LD (384,300 to 385,300 km) from Earth on February 6, 2008.
(450894) 2008 BT18 (~650 meters in diameter) passed 5.9 LD (2.3 million km) from Earth on July 14, 2008.
2008 XK (~12 meters in diameter) may have passed as close as 0.23 LD (89,300 km) from Earth on December 5, 2008, but the nominal orbit suggests it passed nearer to 1.46 LD (560,500 km) from Earth instead.
