Incoming! Tunguska-class bolide to miss Earth by just 22,500km on 15 February 2013

An asteroid the size of a city block is due to come whizzing past Earth closer than any other of its size in recorded history in February next year, according to astronomers.

The asteroid, referred to as 2012 DA14, has a diameter of approximately 45m and an estimated mass of 130,000 tonnes. It was discovered at the start of 2012 and is set to travel between the Earth and our geostationary communication satellites on 15 February 2013. At a distance of just 22,500km this will be the closest asteroid 'fly by' in recorded history.

Asteroid and comet researchers will be gathering at the University of Central Florida (UCF) in Orlando, U.S., to watch the event, but experts say there is no chance of a collision - this time.

"I think perhaps the most important thing about this asteroid is that it reminds us that the threat from such objects is very real," said Jonti Horner, an independent astronomer at the University of New South Wales in Sydney, Australia.

The destructive force of an atomic bomb

It is important to monitor all asteroids that pass close by in case any are on a collision course with Earth. NASA has identified 4,700 asteroids that are potential threats to us, some of which are up to two or three kilometres in diameter.

Any asteroid likely to collide with Earth must have its composition and structure analysed so that it can be deflected, according to a statement from UCF.

A collision with even a small asteroid could be disastrous, with an impact from 2012 DA14 estimated to equal the destructive force of an atomic bomb. "The world's most famous impact crater - the Barringer Crater in Arizona, U.S. - which is about 1,200m in diameter and 170m deep, was formed when an object thought to have been just 50m in diameter hit the Earth," said Horner.

"An incredibly near miss"

"While it's not unusual for asteroids to come close to the Earth, there are a couple of reasons the approach of this one is particularly exciting for astronomers," said Horner.

"Having a 45m space rock pass under 30,000km from the Earth is an incredibly near miss in astronomical terms, which should mean we can learn a great deal about it as it tears past the Earth," he said.

Asteroids offer valuable insight into the formation of our Solar System, according to Humberto Campins who is an asteroid and comet expert at UCF and led the first team to discover ice on an asteroid in 2010.

The asteroid will not pass through our atmosphere and so is unlikely to break up. However, "forces from Earth could change its shape if it is a rubble pile and not a single rock. At this time we do not know which of those two it is," added Campins.

Any change in the composition or shape of the asteroid has the capability to alter its path, which could see it come even closer to Earth in the future.

The asteroid will be too faint to see with the naked eye, although it will be visible through binoculars or a telescope. Additionally, live feeds from telescopes in Spain will offer the public the chance to witness the event.