A celestial body 20 metres in diameter will pass dangerously close -- 8,620 km -- to the Earth's surface in 13 years, an Italian astronomer has said.
The flyby of the asteroid 2013 GM3 April 14, 2026, may bring it within 15,000 km of the Earth's centre, or 8,620 km from the planet's surface, said astronomer Francesco Manca of the Sormano Astronomical Observatory near Milan.
The latter figure is slightly more than one radius of the planet, and within the geostationary orbit of 35,700 km.
The 2013 GM3 was discovered in April by Mount Lemmon Observatory in Arizona, but earlier calculations by NASA showed it would pass 39,000 km from the Earth's surface.
The asteroid may pass as far as 74,000 km from the Earth, Manca said.
More observations are needed to better determine the asteroid's trajectory, the astronomer added.
NASA estimates the probability of 2013 GM3's collision with Earth between 2028 and 2113 at 0.018 percent, or 1 in 5,560.
2013 GM3's size is comparable to that of the meteorite that exploded in the air over the Russian city of Chelyabinsk in February, injuring about 1,500 people, most of whom were injured by glass shattering as a result of the shockwave from the meteorite's passing.