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No. 115

Aircraft carrier-sized asteroid passes close to Earth

A huge asteroid is making its closest approach to Earth in 200 years this morning, but astronomers say there is no chance of a collision.

The 2005 YU55 asteroid is about the size of an aircraft carrier, but will not be visible to the naked eye when it passes about 10:30am AEDT.

"Frankly, for anybody, this is going to be really hard to see. This is 100 times more dim than what the human eye can see. You need a good telescope," NASA spokeswoman Veronica McGregor said.

The near-spherical asteroid often travels in the vicinity of Earth, Mars and Venus, but NASA says today's encounter will be "the closest it has come for at least the last 200 years".

Other asteroids of this size pass by Earth frequently although the last such event happened in 1976 and the next will not happen again until 2028, when an asteroid called 2001 WN5 will skim about halfway between the moon and Earth.

The YU55, which is about 400 metres in diameter, is expected to pass a bit further away: a distance of about 325,000 kilometres from the centre of the Earth.

Ms McGregor says the space rock's closest pass will be off the Pacific Coast of Central America south-west of Guatemala City.

"2005 YU55 is one of the potentially hazardous asteroids that make close approaches from time to time because their orbits either approach or intersect the orbit of the Earth," said Robert McMillan, an associate research scientist at the University of Arizona.

Mr McMillan discovered the asteroid in 2005 as part of the university's Spacewatch Project, a solar-system-scanning group of scientists near Tucson, Arizona.

However, astronomers know from analysing the trajectory of the asteroid that it will not hit Earth this time.