Earth 'shares orbit with asteroid'

The first known Earth Trojan asteroid (AP/Nasa)
12 April 2012

A tiny asteroid has been discovered which runs ahead of Earth on the planet's year-long orbits around the Sun, scientists report.

The discovery of this companion, which measures only about 300 metres across, makes Earth the fourth planet in the solar system that is known to share its orbit with an asteroid.

If Earth and the asteroid were travelling around a clock face, with the Sun in the middle, the asteroid runs about two numbers ahead.

However, the asteroid sometimes ranges so far ahead that it is on the opposite side of the Sun from Earth, said Martin Connors, of Canada's Athabasca University in Alberta. Mr Connors reports the work with colleagues in the latest issue of the journal Nature.

Asteroids are giant space rocks that orbit the Sun, and ones that share an orbit with a planet are called Trojans.

Scientists had previously found a few for Mars and Neptune and nearly 5,000 for Jupiter.

Spotting one in Earth's orbit is difficult from the ground because the potential locations are generally in the daytime sky.

The newfound object, called 2010 TK7, was discovered last year by Nasa's Wise satellite.

Mr Connors and colleagues were able to focus a ground-based telescope in Hawaii on it in April, determining its orbit with enough precision to show it was a Trojan.

Donald K Yeomans, manager of Nasa's Near-Earth Object Programme Office, who did not participate in the discovery, agreed that the asteroid is a Trojan. He said that most scientists suspected Earth had them, adding: "I would guess there's others."

Create a FREE account to continue reading

eros

Registration is a free and easy way to support our journalism.

Join our community where you can: comment on stories; sign up to newsletters; enter competitions and access content on our app.

Your email address

Must be at least 6 characters, include an upper and lower case character and a number

You must be at least 18 years old to create an account

* Required fields

Already have an account? SIGN IN

By clicking Create Account you confirm that your data has been entered correctly and you have read and agree to our Terms of use , Cookie policy and Privacy policy .

This site is protected by reCAPTCHA and the Google Privacy Policy and Terms of Service apply.

Thank you for registering

Please refresh the page or navigate to another page on the site to be automatically logged in