433 Eros

433 Eros is a near-Earth asteroid discovered in 1898 and the first asteroid orbited and landed on by a spacecraft, NASA’s NEAR Shoemaker.

NEAR Shoemaker: A NASA spacecraft that orbited 433 Eros and made a controlled landing on its surface in 2001. Its orbital survey and landing revealed Eros in unprecedented detail.
Near-Earth object: An asteroid or comet whose orbit brings it close to Earth’s orbital region. Eros belongs to this population because its solar orbit approaches Earth’s.
Gustav Witt: A German astronomer who discovered 433 Eros in 1898. Witt detected Eros at the Urania Observatory in Berlin.
Astronomical unit: The average distance between Earth and the Sun, defined as exactly 149,597,870.7 kilometers. Eros’s close approaches once enabled estimates of the Earth–Sun distance.
433 Eros orbit: The path followed by 433 Eros around the Sun, crossing near Earth’s orbital region. Its orbit made Eros a target for close spacecraft study and a monitored near-Earth object.
Asteroid rotation: The spinning motion of an asteroid about its axis. Eros’s rotation affects how sunlight warms its surface and how its shape is inferred.
Auguste Charlois: A French astronomer who independently discovered 433 Eros in 1898. Charlois found the asteroid independently on the same night as Witt.
Radar astronomy: The study of Solar System objects by transmitting radio waves and analyzing their echoes. Radar observations of Eros refined its distance and orbit.
Eros landing: The 2001 controlled touchdown of NEAR Shoemaker on the surface of 433 Eros. The mission ended with an unplanned but successful surface encounter.
Yarkovsky effect: A small change in an asteroid’s orbit caused by the uneven emission of absorbed heat. This force can slowly alter the paths of near-Earth asteroids such as Eros.

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