Earthlings can breathe a sigh of relief after US space agency Nasa confirmed the planet was "safe" from a once-feared asteroid for the next 100 years at least.

Nasa had deemed Apophis to be one of the most dangerous asteroids to Earth after its discovery in 2004.

Close calls in 2029 and 2036 were predicted and later ruled out. A slight threat still remained for 2068.

But now Nasa has dismissed that threat based on new analysis of the asteroid.

"A 2068 impact is not in the realm of possibility any more, and our calculations don't show any impact risk for at least the next 100 years," Davide Farnocchia, a scientist who studies near-Earth objects for Nasa, said in a statement on Friday.

Named after the ancient Egyptian god of chaos and darkness, Apophis is estimated to measure 340m (1,100ft) across - about the length of three UK football pitches.

Although most asteroids are found in the belt of space between Mars and Jupiter, not all of them reside there. Apophis belongs to a group known as the Aten family. These do not belong to the asteroid belt and spend most of their time inside the orbit of the Earth, placing them between our planet and the sun.

That makes them particularly dangerous because they spend the majority of their orbit close to the sun, whose overwhelming glare obscures them to telescopes on Earth – rather like a second world war fighter ace approaching out of the sun.