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Asteroids have historically been observed from Earth. The first close-up observation of an asteroid was made by the Galileo spacecraft. Several dedicated missions to asteroids were subsequently launched by NASA and JAXA, with plans for other missions in progress. NASA's NEAR Shoemaker studied Eros, and Dawn observed Vesta and Ceres.
This is a list of asteroids that have impacted Earth after discovery and orbit calculation that predicted the impact in advance. As of December 2024, all of the asteroids with predicted impacts were under 5 m (16 ft) in size that were discovered just hours before impact, and burned up in the atmosphere as meteors.
Outside the top four, the ranking of all the asteroids is uncertain, as there is a great deal of overlap among the estimates. The largest asteroids with an accurately measured mass, because they have been studied by the probe Dawn, are 1 Ceres with a mass of (939.3 ± 0.5) × 10 18 kg, and 4 Vesta at (259.076 ± 0.001) × 10 18 kg.
The number of asteroids brighter than H = 25, which corresponds to about 40 m (130 ft) in diameter, is estimated at 840,000 ± 23,000 —of which about 1.3 percent had been discovered by February 2016; the number of asteroids brighter than H = 30 (larger than 3.5 m (11 ft)) is estimated at 400 ± 100 million—of which about 0.003 percent had ...
The missed asteroids do tend to be small, and missing small asteroids is relatively unimportant. By contrast, missing a large day-side impacting asteroid is highly problematic, with the unpredicted mid-size Chelyabinsk meteor providing a mild real-life example.
Satellites in geostationary orbit. From the list in the first section, these are the closest known asteroids per year that approach Earth within one lunar distance.More than one asteroid per year may be listed if its geocentric distance [note 1] is within a tenth of the lunar distance, or 0.10 LD.
These are lists of asteroids, e.g. by discoverer or by number. See list of minor planets for an overview and numbering and naming conventions . Pages in category "Lists of asteroids"
Unless specified otherwise, subcategorized asteroids should be sorted using a 0-padded 6-digit sortkey based on their numerical designation. Otherwise, their provisional designation should be used. For example, 493 Griseldis would use [[Category:Small-asteroids collision|000493]]. (6178) 1986 DA would use [[Category:Radar-imaged asteroids|006178]].