Football field-sized asteroid zips by Earth this weekend

Astronomers have discovered yet another big asteroid that is going to fly by the Earth.

Asteroid 2013 ET was found on Sunday, March 3rd, by scientists working with the Catalina Sky Survey. It is estimated at being around 100 metres in diameter (roughly the length of a football field), and it will pass us at a distance of about 960,000 kilometers (about 2.5 times the distance between Earth and the Moon), flying at a speed of around 12 km/s.

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This six-second video was captured by the astronomers, tracking the asteroid as the stars move in the background:

So, passing by us at nearly 1 million kilometres away it isn't exactly a close shave, and it goes without saying (although I'm going to say it anyway) that it has no chance of hitting Earth. However, it is remarkable due to discovering that big of an asteroid only about a week before it arrives here.

That would certainly give sufficient warning to evacuate anyone near the projected point of impact, and you would definitely need to get everyone out of the area. The amount of damage that a 100 m asteroid would do depends on what it's made of.

If it's made of porous rock, it would explode in mid-air (like the one did over Chelyabinsk, Russia, last month) about 2.5 kilometres above the ground with the force of a 13 megaton bomb — about 10 times closer to the ground and over 25 times as powerful than the one over Chelyabinsk — meaning it could level a small city.

If it's dense rock, it actually hits the ground, detonating with the force of a 4.4 megaton bomb. This is lower than the air-burst of the porous rock asteroid because it would lose more energy as it passed through the entire depth of the atmosphere, but it would still cause massive damage to a major city, leaving a crater more than a kilometre wide, and it would shake the surrounding area like a magnitude 5.0 earthquake.

If it happened to be an iron asteroid, the effect would be catastrophic. It would hit the ground with the force of a 66 megaton bomb, and would be the biggest explosion the human race has ever witnessed on this planet — bigger than the biggest nuclear bomb we've ever set off (Tsar Bomba, 57 megatons, on Oct 30, 1961, by the U.S.S.R.). The crater left behind afterward would be over 2.5 kms wide, and over 500 m deep. It would shake the ground like a magnitude 6 earthquake, leveling everything in a 10 kilometre radius and damaging everything out to about 30 kilometres away.

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Finding this asteroid a week before it flies by us is close to the goal of astronomers that are in the process of building early warning systems, but they want to get a week's advanced warning for objects half the size of 2013 ET, and probably up to 2 weeks for something of its size.

You can watch 2013 ET as it passes by the Earth, thanks to a live webcast by The Virtual Telescope Project, starting at 2 p.m. EST on Friday, March 8th. Click here.

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