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An asteroid a little smaller than the CN Tower is hurtling toward earth and astronomers have their cameras ready for a spectacular glimpse.

Called 2005 YU55, the asteroid will nudge closer to earth than the moon, passing by just 325,000 kilometres away.

Although modern technology will give astronomers the best-ever look at the travelling piece of cosmological history, there is no fear it will actually smack into earth.

"At one time we had classified 2005 YU55 as a potential threat," said Steve Chesley, a scientist at NASA Jet Propulsion Laboratory's Near-Earth Object Program Office.

Radar tracking last month, with the asteroid 2.3 million kilometres away, meant "we were able to rule impacts out entirely for the next 100 years."

Asteroids have been this close before. But "nobody has seen asteroid 2055 YU55 at four-metre resolution yet," JPL scientist Lance Benner told the Star in an email.

"We did not have the foreknowledge and technology to take advantage of the opportunity," said JPL scientist Barbara Wilson "When it flies past, it should be a great opportunity for science instruments on the ground to get a good look."

YU55 is due to arrive "from a sunward direction" on Nov. 8 and the best time to see it will be later that day and into Nov. 9.

"This is a C-type asteroid, and those are thought to be representative of the primordial materials from which our solar system was formed," Wilson said in a NASA release.

"This flyby will be an excellent opportunity to test how we study, document and quantify which asteroids would be most appropriate for a future human mission."

A long-distance view in 2010 revealed "a dark, rocky object with a composition similar to those of carbonaceous chondrite meteorites," said Benner.

This time, "we might see large boulders, possibly craters, hills and valleys and perhaps some features that haven't been seen before."

Discovered in December 2005, the asteroid is about 400 metres wide.