WISE finds Trojan asteroid sharing Earth’s orbitJuly 28, 2011
Observations taken by NASA’s Wide-field Infrared Survey Explorer mission (WISE) have revealed the first known “Trojan” asteroid orbiting the Sun along with the Earth. Trojans are minor planets or asteroids that share an orbit with a larger planet, positioned at a stable point in front of or behind it.
Because they’re permanently leading or trailing the planet (following the same orbit) they can never collide with it. In our solar system, Trojans also share orbits with Neptune, Mars and Jupiter, and two of Saturn’s moons also have Trojans.
Scientists had predicted Earth would have Trojans, but they have been difficult to find because they are relatively small and appear near the Sun from Earth’s point of view.
“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 asteroid is roughly 1,000 feet (300 meters) in diameter. It has an unusual orbit that traces a complex motion near a stable point in the plane of Earth’s orbit, although the asteroid also moves above and below the plane. The object is about 50 million miles (80 million kilometers) from Earth.
“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.”
Read the full article on NASA’s WISE Mission Page