Earth has joined a group of planets like Jupiter, Neptune and Mars which have Trojan asteroids as companions as they move around the sun in their orbits.

It has been speculated for a long time that Earth has a cluster of Trojan asteroids, or space rocks that typically sit in the Lagrange points 60 degrees ahead of or behind the planets in their orbits. Jupiter has around 1,000 Trojans, or rocks that dance along in its orbit.

The asteroid, which is named 2010 TK7, is the first confirmed Trojan asteroid in Earth's Lagrange points. It was discovered recently by NASA's WISE telescope.

The Trojan, whose behavior is chaotic according to the scientists, is 300 meters across in size and is ahead of Earth in its orbit by about 50 million miles. "It's as though the Earth is playing follow the leader," said Amy Mainzer, the principal investigator of NEOWISE at NASA's Jet Propulsion Laboratory, describing how Earth and the Trojan asteroid move along in the orbit. "Earth is always chasing this asteroid around."

Scientists said these asteroids could be possible future destinations for space missions. They could contain elements that rare on Earth's surface as well. However, astronomers say 2010 TK7 may not be an ideal target for a mission as it 'travels above and below the plane of Earth's orbit,' according to

However, the discovery has confirmed the existence of Earth Trojans, and some of these could qualify for a mission in future. "We could be mining these things one day," said study co-author Martin Connors, an astronomer at Athabasca University in Canada.

Also, scientists have assured that the new space rock will not pose any danger to Earth as it sits on a gravitational "sweet spot".