Earth’s first Trojan asteroid found

National Geographic : Earth’s first Trojan asteroid, 2010 TK7, has been discovered. About 1000 feet wide, it travels with Earth around the Sun at a distance of about 50 million miles, writes Ker Than for National Geographic. Trojans are bodies that exist in orbital “sweet spots” between Lagrange points—spots where the gravitational pull of the planet and that of the Sun combine to allow the Trojan to maintain its position relative to both of them. Trojan asteroids have been found around Mars, Jupiter, and Neptune; although it had long been thought that Earth should also have them, they proved difficult to find because any Trojan, from the perspective of an observer on Earth, will reside in the general direction of the Sun. Martin Connors, an astronomer at Athabasca University in Canada, and colleagues made the discovery with NASA’s Wide-field Infrared Survey Explorer (WISE) telescope . Connors likened the asteroid’s orbit to the path of an orange held at arm’s length by a person riding a Ferris wheel.