An asteroid the size of a large house will zip within 12,900 kilometres of the Earth at about midday London time on Monday.
Called 2011 MD, the asteroid was discovered late on Wednesday by an automated asteroid-hunting telescope run by the MIT Lincoln Laboratory's LINEAR programme, which had already discovered well over 2000 near-Earth objects. In just over 24 hours, four other groups confirmed the discovery.
The Minor Planet Center at Harvard University does not rate 2011 MD as potentially hazardous because its size - estimated from its brightness - is only 8 to 18 metres. That would make an impressive explosion if it hit the atmosphere, but it wouldn't reach the ground.
On its current pass, 2011 MD won't hit Earth's atmosphere. It will come inside the orbits of many communications and spy satellites, but will still be some 12,500 kilometres away from the International Space Station. However, Spaceweather.com reports that the encounter is close for Earth's gravity to "sharply alter the asteroid's trajectory".
Discoveries of small near-Earth asteroids have soared since the year 2000 with the growth of automated sky surveys following in the footsteps of LINEAR, which found its first asteroid in 1996.
As of June, stats compiled by NASA's Jet Propulsion Laboratory in Pasadena, California, show more than 8000 known asteroids in near-Earth orbits. More than 7000 of these are smaller than a kilometre across and almost 1000 are smaller than 30 metres.
Asteroid counts are expected to soar further as the Pan-STARRS survey comes on line; so far, only one of its four planned 1.8-metre telescopes has been completed, and it has only been fully operational for a year.
Unfortunately 2011 MD won't put on much of a show for amateur astronomers, astronomy magazine Sky and Telescope reports.
The logistics for seeing the moment of closest approach are extraordinarily poor. It takes place in broad daylight not far off the coast of Antarctica, almost 2000 miles south-southwest of South Africa
However, backyard astronomers with telescopes in New Zealand and Australia will be able to watch it in the night sky until half an hour earlier.