Astronomers have spotted an asteroid close to Earth and moving in the same orbit around the Sun. The rock is 200-300 m wide and sits in front of our planet and is non-threatening. Currently, it is about 80 million km from Earth.

2010 TK7 was discovered by Nasa's Wise telescope and reported in Nature journal this week.

The discovery implies that it is likely that there are other Trojans waiting to be found. As the 2010 TK7 travels too far above and below Earth's orbit, too much fuel is needed to reach it.

Trojan asteroids are prospective targets for astronaut missions.

An orbiting telescope that is sensitive to infrared light was used to spot the asteroid and follow-up work on the Canada-France-Hawaii Telescope has confirmed that 2010 TK7 is an asteroid.

Jupiter, Neptune and Mars all have similar collections of rocks ahead of or behind the planets in their orbits. Jupiter has an excess of 1,000 rocks.

"We think that there are others which will be very close to the Earth and have motions that make them relatively easy to reach. So, they could be potential targets to go to with spacecraft," Christian Veillet from the Canada-France-Hawaii Telescope and a co-author on the Nature study told BBC News.