Asteroid to miss Earth in 2040, NASA says

Uncertainties about the orbit of the asteroid, known as 2011 AG5, previously allowed for a less than a 1 per cent chance it would hit the Earth in February 2040, NASA said.

Previously, scientists estimated that the risk of this 140-meter-diameter, about the length of two football fields, asteroid colliding with the Earth was as high as one in 500.

If this object were to collide with the Earth it would have released about 100 megatons of energy, several thousand times more powerful than the atomic bombs that ended World-War II. Statistically, a body of this size could impact the Earth on average every 10,000 years.

The observations, using the Gemini North telescope on Mauna Kea, Hawaii, were especially challenging, said team-member Richard Wainscoat.

"These were extremely difficult observations of a very faint object. We were surprised by how easily the Gemini telescope was able to recover such a faint asteroid so low in the sky," Wainscoat said in a Gemini statement.

The Gemini observations were made on October 20, 21, and 27, 2012, it said.

In addition to multiple observations since the asteroid's discovery, the team had also acquired images about two weeks earlier with the University of Hawaii 2.2-meter telescope also on Mauna Kea