A GIGANTIC asteroid the size of a mountain will speed past Earth later this month.

Dubbed 1998 OR2, the space rock will be so big that amateur skygazers should be able to spot it as it streaks across the heavens on April 29.

Nasa has classed the object as "potentially hazardous" although experts do not believe it will hit our planet.

Instead, OR2 is expected to sail safely past at a distance of around 4million miles – or about 17 times the distance from Earth to the Moon.

That may sound like a long way, but it's close enough that Nasa classes the asteroid as a "Near Earth Object" (NEO).

Scientists are keeping a very close eye on it just in case.

The space rock is not expected to collide with EarthCredit: Getty - Contributor

At up to 2.5 miles long, the asteroid is taller than Japan's enormous Mount Fuji.

That makes it large enough to spot with a telescope on a clear night.

It is currently only visible with a professional telescope.

The Virtual Telescope Project will be screening a livestream of the asteroid on April 28, starting at 2pm ET (18:00 GMT).

Apparently, the asteroid will look like a "slow-moving star" as it zips past our planet.

Nasa considers anything passing within 120million miles of Earth a NEO.

Astronomers are currently tracking nearly 2,000 asteroids, comets and other objects that threaten our pale blue dot, and new ones are found every day.

Earth hasn't seen an asteroid of apocalyptic scale since the space rock that wiped out the dinosaurs 66million years ago.

However, smaller objects capable of flattening an entire city crash into Earth every so often.