Astronomers have spotted a 'potentially hazardous' asteroid less than one month before it is due to pass close to Earth.
The object, given the name '2010 ST3', is 150 metres in diameter and will pass within four million miles of Earth in mid-October.
It was discovered using the Panoramic Survey Telescope & Rapid Response System (Pan-STARRS) PS1 telescope in images taken on September 16th, when it was about 20 million miles away.
It is the first 'potentially hazardous object' (PHO) to be discovered by the Pan-STARRS survey, using a new telescope designed to scan the skies for dangerous asteroids. Two images of 2010 ST3 (circled in green) taken by PS1 about 15 minutes apart on the night of Sept. 16
'Although this particular object won't hit Earth in the immediate future, its discovery shows that Pan-STARRS is now the most sensitive system dedicated to discovering potentially dangerous asteroids,' said Robert Jedicke, a University of Hawaii member of the PS1 Scientific Consortium, who is working on the asteroid data from the telescope.
'This object was discovered when it was too far away to be detected by other asteroid surveys,' Jedicke noted.
Most of the largest PHOs have already been catalogued, but scientists suspect that there are many more under a mile across that have not yet been discovered.
These could cause devastation on a regional scale if they ever hit our planet. Such impacts are estimated to occur once every few thousand years.