Amateur astronomers will soon get the chance to observe a half-kilometre-wide asteroid as it safely passes close to Earth on its 200-year-long orbit.

The massive asteroid, awkwardly dubbed 2004 BL86, will be visible through amateur telescopes on Monday night as it flies by at about three times the distance from the Earth to the moon. Most stargazers with a backyard telescope should be able to spot it Monday night as it moves across the stars in the sky.

And for those curious stargazers lacking a telescope, the company Slooh.com is providing a livestream of the passing.

According to NASA, the asteroid will make its closest approach to Earth at about 11:19 p.m. ET.

Don Yeomans, of NASA's Jet Propulsion Laboratory, says the asteroid likely won't come around again for at least 200 years.

"It's a relatively close approach by a relatively large asteroid, so it provides us a unique opportunity to observe and learn more," Yeomans said in a NASA news statement.

He added that the asteroid poses no threat to Earth.

NASA's astronomers will be watching the asteroid through their telescopes and studying it with radar instruments as it cruises past our planet.

"We know almost nothing about the asteroid, so there are bound to be surprises," NASA radar expert Lance Benner said.

The approximately 0.5-kilometre-wide asteroid is large for a chunk of space rock, but still much smaller than the 10-kilometre-wide asteroid that some believe triggered the extinction of the dinosaurs 65 million years ago.

NASA says 2004 BL86 will be the largest asteroid to pass this close to Earth until 2027, when another one is expected to cruise through.