Science & Environment

Asteroid 2012 DA14 in record-breaking Earth pass

An asteroid as large as an Olympic swimming pool has raced past the Earth at a distance of just 27,700km (17,200mi) - the closest ever predicted for an object of that size.

It passed far closer even than the geosynchronous satellites that orbit the Earth, but there was no risk of impacts or collisions.

Its closest approach was at 19:25 GMT.

For regions in darkness, it should have remained visible until about midnight through good binoculars or a telescope.

The asteroid's arrival was preceded by a damaging meteor event in Russia on Friday - but indications from the meteor's path suggest that the two events are entirely unrelated - just a "cosmic coincidence", as Alan Fitzsimmons of Queens University Belfast told BBC News.

The asteroid orbits the Sun in 368 days - a period similar to Earth's year - but it does not orbit in the same plane as the Earth.

As it passes - at 7.8km/s (17,450 mi/hr) - it will come from "under" the Earth and return back toward the Sun from "above".

It passed directly over the eastern Indian Ocean, making for the best viewing in Eastern Europe, Asia and Australia.

But keen viewers everywhere used several live streams of the event on the internet, including a feed from the Jet Propulsion Laboratory at Nasa.

2012 DA14 was first spotted in February 2012 by astronomers at the La Sagra Sky Survey in Spain - once a fairly small-scale, amateur effort to discover and track asteroids that has in recent years become a significant contributor to our knowledge of these "near-Earth objects".

They caught sight of the asteroid after its last pass, at a far greater distance.

From their observations, they were able to calculate the asteroid's future and past paths and predict Friday's near-miss - which will be the closest the object comes for at least 30 years.

Prof Fitzsimmons said that it is a scientific opportunity not to be missed.

"When asteroids come this close, it's very important to try to learn about them - it's become so bright, so it's so easy to study," he told BBC News.

"We get an additional insight into these small objects, which are the most likely impactors on Earth."

The notion that it is these smaller, tens-to-hundreds of metres-sized objects that pose the greatest potential threat to Earth is explored in the BBC feature article Can we know about every asteroid? .

The asteroid was only visible from some regions on Earth. Click through these maps produced by Dr Geert Barentsen, of the University of Hertfordshire, to see when the asteroid was visible in different areas:

For skywatchers in the UK, the graphic below indicates roughly where in the northern sky to try to spot 2012 DA14.

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