Trojan asteroid caught circling Earth, the Greeks deny involvement

PASADENA, Calif. – Astronomers studying observations taken by NASA’s Wide-field Infrared Survey Explorer (WISE) mission have discovered the primary known “Trojan” asteroid orbiting the sun in addition to Earth.

Trojans are asteroids that share an orbit with a planet near stable points in front of or behind the planet. Because they constantly lead or follow within the same orbit because the planet, they never can 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 have to have Trojans, but they’ve been difficult to locate because they’re relatively small and seem near the sun from Earth’s standpoint.

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

The WISE telescope scanned the complete sky in infrared light from January 2010 to February 2011. Connors and his team began their look for an Earth Trojan using data from NEOWISE, an addition to the WISE mission that focused partly on near-Earth objects, or NEOs, akin to asteroids and comets. NEOs are bodies that pass within 28 million miles (45 million kilometers) of Earth’s path across the sun. The NEOWISE project observed greater than 155,000 asteroids usually belt between Mars and Jupiter, and greater than 500 NEOs, discovering 132 that were previously unknown.

The team’s hunt led to 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.

The asteroid is roughly 1,000 feet (300 meters) in diameter. It has an unusual orbit that traces a fancy motion near a stable point within the plane of Earth’s orbit, although the asteroid also moves above and below the plane. The item is ready 50 million miles (80 million kilometers) from Earth. The asteroid’s orbit is easily-defined and for no less than the following 100 years, this may not come in the direction of Earth than 15 million miles (24 million kilometers). An animation showing the orbit is accessible at: http://www.nasa.gov/multimedia/videogallery/index.html?media_id=103550791 .

“It’s as if 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.”

A handful of different asteroids even have orbits identical to Earth. Such objects can make excellent candidates for future robotic or human exploration. Asteroid 2010 TK7 seriously isn’t an even target since it travels too far above and below the plane of Earth’s orbit, which might require quite a lot of fuel to achieve it.

“This observation illustrates why NASA’s NEO Observation program funded the mission enhancement to process data collected by WISE,” said Lindley Johnson, NEOWISE program executive at NASA Headquarters in Washington. “We believed there has been great potential to seek out objects in near-Earth space that had not been seen before.”