8 Nov 2011

Close encounter with asteroid - but NZ won't see it

9:47 pm on 8 November 2011

An asteroid the size of an aircraft carrier will be passing close to Earth on Wednesday but star gazers in New Zealand will not be able to see it.

Asteroid 2005 YU55 - which is measure 400 metres across - will pass within 325,000 kilometres of earth at about 11 am on Wednesday, closer than the Moon is to Earth.

Vicki Irons of the Carter Observatory in Wellington says it will be too light for anyone in New Zealand to spot it.

She says observors in the northern hemisphere - where it will be night - will have a much better view of the visitor from space.

Ms Irons says, as it hurtles past, the space rock will be much closer to the Moon than the Earth, passing about 60,000 kilometres from the moon.

The BBC reports it is the closest that an asteroid of this size has come to the planet since 1976, although on that occasion, astronomers did not have prior warning of the fly-by.

This asteroid is being tracked by astronomers taking advantage of a rare opportunity to study it in detail and learn more about its future path.

Alan Gilmore of Canterbury University's Mt John Observatory told Checkpoint that for astronomers specialising in asteroids, this is quite a big deal as it will be possible to analyse light from it to see what it is made of - an advantage if it ever becomes a threat to Earth in future.

He says radar researchers will be able to measure its speed and make a much tighter calculation of its orbit.

They will then be able extrapolate out to see if there is any likelihood of it posing a threat.

Scientists at the US space agency NASA say, despite the close proximity of Wednesday's asteroid, there is no danger of a collision with Earth.

If an asteroid of that size did hit the planet, scientists predict it would cause a four kilometre-wide crater, a magnitude seven earthquake and, if it hit water, create a tsunami 21 metres high that would spread within 96 kilometres of the crash site.