Trojan Asteroid Shares Orbit With Earth

07/29/2011 02:48 PM ET

Asteroid Earth - Astronomers have found the first “Trojan” asteroid that shares the same orbit around Earth. Trojans are located near stable points in front of or behind the planet. However, they can never collide with the planet because they constantly lead or follow with the planet.

“These asteroids dwell mostly in the daylight, making them very hard to see,” said Martin Connors of Athabasca University in Canada, lead author of a new paper on the discovery in the July 28 issue of the journal Nature. “But we finally found one, because the object has an unusual orbit that takes it farther away from the sun than what is typical for Trojans. WISE was a game-changer, giving us a point of view difficult to have at Earth’s surface.”

The astronomers were able to find the asteroid studying data from NASA’s Wide-field Infrared Survey Explorer (WISE). WISE is a NASA infrared-wavelength astronomical space telescope launched on 14 December 2009, and decommissioned on February 17, 2021 when its transmitter was turned off. Results of the full survey will be released by March 2012.

Dubbed the 2010 TK7, it has an absolute magnitude of about 20.6. It has an estimated diameter of about 300 meters, based on an assumed albedo of 0.1. No spectral data is yet available to shed light on its possible composition. The asteroid has an orbital period of 365.389 days, comparable to Earth’s 365.256 days. Trojan objects had previously only been observed in the orbits of Mars, Jupiter, Neptune and several moons of Saturn.

“It’s as though Earth is playing follow the leader,” said Amy Mainzer, the principal investigator of NEOWISE at NASA’s Jet Propulsion Laboratory in Pasadena, Calif. “Earth always is chasing this asteroid around.”

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