Bus-sized asteroid 2017 SX17 gives Earth a close shave

An asteroid the size of a bus gave Earth a close shave today by shooting past at less than a quarter the distance of the Moon.

The 60-inch (1.5 metre) telescope on Mt Lemmon, Arizona, that watches for asteroids as part of the Catalina Sky Survey. Image credit: Catalina Sky Survey, University of Arizona

The giant chunk of space rock, labelled 2017 SX17, was only discovered last week, on Friday, September 29th, by a telescope watching for threatening asteroids, dubbed Near Earth Objects, in Arizona.

At its closest, the cosmic missile came was only about 88.320 km (54,880 miles) away at 11.20am, UK time. Its size was estimated as being from 6.5 to 15 metres (20-50ft) wide by NASA’s Center for Near Earth Object Studies (CNEOS).

The asteroid was detected by a 1.5-metre (60-in) telescope on Mt Lemmon in the Santa Catalina Mountains, Arizona, that is part of the Catalina Sky Survey.

The asteroid is part of number known as the Apollo group, named after the first of its kind, 1862 Apollo, which was discovered in the 1930s by German astronomer Karl Reinmuth.

Since then, more than 8,000 have been identified, including one that was unknown before it exploded over the Russian city of Chelyabinsk in 2013, shattering windows and injuring around 1,000 people.

Near Earth Asteroid 2012 TC4 appears as a dot at the centre of this composite of 37 individual 50-second exposures obtained with the European Southern Observatory’s Very Large Telescope, in Chile. The asteroid is marked with a circle for a better identification. The individual images have been shifted to compensate for the motion of the asteroid, so that the background stars and galaxies appear as bright trails. Image credit: Credit: ESO / ESA NEOCC / Olivier Hainaut (ESO), Marco Micheli (ESA) and Detlef Koschny (ESA)

Another asteroid, discovered then lost in 2012, will fly close by on October 12 at 5.42 UT. Uncertainty over its orbit had led the European Space Agency to warn that there was a one in a million chance that it could collide with Earth.

However, the asteroid, which is estimated to be up to 30 metres (100 ft) across, was picked up again by the European Southern Observatory’s Very Large Telescope on July 27.

The asteroid was shining at a faint 26.8 magnitude, making it the faintest asteroid to be measured, according to ESO.

Fresh analysis of its orbit shows there is no chance of an impact. The asteroid will fly by at a distance of 49,000 km (31,000 miles).

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