Astronomers from the Mount Lemmon Survey team first spotted the rock on Wednesday, according to an alert by Minor Plant Center, which is part of the International Astronomical Union.
Nasa scientists and researchers across the world keep a constant look-out for potentially dangerous asteroids that could crash into Earth - with deadly consequences.
Former astronaut Ed Lu said earlier this year that it was only "blind luck" that the planet had not suffered a catastrophic hit from an asteroid.
He told Wired.co.uk: "While most large asteroids with the potential to destroy an entire country or continent have been detected, less than 10,000 of the more than a million dangerous asteroids with the potential to destroy an entire major metropolitan area have been found by all existing space or terrestrially-operated observatories.
"Because we don't know where or when the next major impact will occur, the only thing preventing a catastrophe from a 'city-killer' sized asteroid has been blind luck."
In 2013 over 1,000 people were injured after an asteroid exploded above the Russian city of Chelyabinsk.
- UK Independent
