LOS ANGELES, July 28 — Astronomers said Wednesday they have discovered the first known "Trojan" asteroid orbiting the sun along with Earth.
The discovery was made through observations taken by NASA's Wide-field Infrared Survey Explorer (WISE) mission, according to NASA's Jet Propulsion Laboratory (JPL) in Pasadena, California.
Trojans are asteroids that follow the same orbit as a planet near stable points in front of or behind the planet. Because they constantly lead or follow in the same orbit as the planet, they never collide with it. In our solar system, Trojans also share orbits with Neptune, Mars and Jupiter. Two of Saturn's moons share orbits with Trojans.
Scientists had predicted Earth should 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.
The team's search resulted in two Trojan candidates. One called 2010 TK7 was confirmed as an Earth Trojan after follow-up observations with the Canada-France-Hawaii Telescope on Mauna Kea in Hawaii, JPL said.
"These asteroids dwell mostly in the daylight, making them very hard to see," said Martin Connors of Athabasca University in Canada. "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."
Some other asteroids also have orbits similar to Earth, and they would be ideal objects for future human or robotic exploration, JPL said.
"We believed there was great potential to find objects in near-Earth space that had not been seen before," said Lindley Johnson, NEOWISE program executive at NASA Headquarters in Washington. (PNA/Xinhua)