Astronomers from the Armagh Observatory in Northern Ireland have found that a recently discovered asteroid has been following Earth in its motion around the Sun for at least the past 250,000 years, and may be intimately related to the origin of our planet.
The asteroid first caught the eye of the scientists two months after it was found by the WISE infrared survey satellite, launched in 2009 by the United States. "Its average distance from the Sun is identical to that of the Earth," says Dr Christou, "but what really impressed me at the time was how Earth-like its orbit was." Most near-Earth Asteroids -- NEAs for short -- have very eccentric, or egg-shaped, orbits that take the asteroid right through the inner solar system. But the new object, designated 2010 SO16, is different. Its orbit is almost circular so that it cannot come close to any other planet in the solar system except Earth.