Lincoln Laboratory discovers inner Earth orbit asteroids

The first known inner Earth orbit (IEO) asteroid has been formally named (163693) Atira by its discoverers at MIT Lincoln Laboratory in support of NASA's Near Earth Object Observations (NEOO) Program.

This unique asteroid was discovered 11 February 2003 by the Lincoln Near-Earth Asteroid Research (LINEAR) program, which operates jointly out of Socorro, New Mexico, and Lexington, Massachusetts. Atira is named after a Native American goddess of the Earth and the evening star.

Originally designated 2003 CP20 at the time of its discovery, Atira was the first asteroid known to always remain interior to the Earth's orbit. Atira is estimated to be 1 to 2 kilometers in diameter and takes 233 days to orbit the Sun, crossing the path of Venus along the way, but never coming as close to the Sun as Mercury.

Image of Aitia in the night skyAtira (indicated in red) was discovered only 73 degrees away from the Sun in longitude. This is much closer to the Sun than is typical for discoveries, given the difficulty of searching this part of the night sky with a telescope. Atira was also located a slightly unusual 56 degrees north of the ecliptic. Click on this image to view an animation of Atira moving across the sky. The above photograph is a compilation of five single images; the animation shows the five images in sequence.

In the five years since the discovery of Atira, seven more IEO asteroids with similar orbital characteristics have been discovered. These eight objects make up the fourth and newest class of near-Earth asteroids. Following tradition, this newest class of asteroids is now known as Atiras in recognition of the first named body in the class. The other three classes are Atens, Apollos, and Amors, named respectively in recognition of Aten (2062) discovered in 1976, and Apollo (1862) and Amor (1221), both discovered in 1932.

Posted February 2009

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