Earth and asteroid 2010TK7 orbiting the sun together. The path of the asteroid is traced in green.

Astronomers have spotted a huge lump of rock that hurtles through space ahead of the Earth in its orbit around the sun.

The rock, which is 300 metres across, is known as a “Trojan asteroid” because it shares Earth’s orbit but remains far enough away it will never collide with the planet.

Trojan asteroids can follow planetary orbits if they stay close to positions 60 degrees ahead or behind the planet. At these points, gravitational forces and orbital motion balance each other, producing stable relative locations in space.

Martin Connors at Athabasca University in Alberta, Canada, used Nasa‘s Wide-field Infrared Survey Explorer satellite and ground-based telescopes to identify the Trojan asteroid, named 2010TK7. The study is published in Nature.

Similar Trojans have been found orbiting the sun in step with Jupiter, Neptune and Mars.