Asteroid fly-by visible from Earth

Scientists want to learn more about these wandering space rocks

A close encounter with a small asteroid this weekend could be viewed with binoculars or a small telescope, say experts.

The space rock, 800 metres (half a mile) across and designated 2002 NY40, will make its closest approach on Sunday.

The opportunity for amateur skywatchers to get such a close-up view of an asteroid occurs only once every half-century.

	Enlarge image
Asteroid Fly-by

The nearest the asteroid will get is within 530,000 kilometres (330,000 miles) - slightly farther away than the Moon.

Future pass

Its track in the sky will pass close by the bright star Vega and through the constellation of Hercules.

It will be significantly dimmer than even the faintest star visible with the naked eye.

European skywatchers will catch their best glimpse in the early hours of Sunday. For viewing from North America, the best time to watch will be on Saturday evening.

Scientists will be able to use the close approach to plot the course of the asteroid over the years to come.

They say there is a minute risk - one in 500,000 - that the rock could strike Earth in 2022, but the new measurements could show it will definitely miss us.

Drawing skills

Jay Tate, from the Spaceguard UK observatory in Powys, said that with a little effort, it should be possible to detect the movement of the asteroid.

It's not groundbreaking science for us, but this is an opportunity for thousands of amateur astronomers

Jay Tate, Earthguard UK

He told BBC News Online: "People should look at the right area of the sky through their binoculars, and make a rough drawing of the position of all the bright objects.

"Then they should look again five minutes or so later and see which of them has moved.

"This asteroid won't look anything like a normal shooting star, or even a satellite.

"It's not groundbreaking science for us, but this is an opportunity for thousands of amateur astronomers to see something like this."

Spin rate

He said that measurements taken by experts might show the rate at which the rock was spinning in space, giving clues to its composition.

Other astronomers may also be able to produce three-dimensional maps of its surface.

The asteroid fly-by follows last month's reports of another, bigger, rock, called 2002 NT7, which scientists speculated might be a candidate for colliding with the Earth in 2019.

Further data revealed, however, that there was no chance of this happening.