An asteroid the size of a passenger aircraft has been detected after passing extremely close to Earth.

What’s worrying about that sentence is the word ‘after’. It was completely undetected until three days after it had been at its closest point to our planet.

According to EarthSky’s Eddie Irizarry, the asteroid named 2017 OO1 was detected by  the ATLAS-MLO telescope in Hawaii on 23 July 2017.

The only problem being that had it been on a collision course for Earth, it would have actually struck us three days earlier on the 20 July.

While it’s important to note that the asteroid did pass at some considerable distance (76,448 miles), that’s still just a third of the distance between Earth and the Moon.

So just how much damage would an asteroid of that size done to Earth? Well as Irizarry points out, it looks to have been about three times the size of the Chelyabinsk meteorite that injured almost 1000 people when it came crashing down to Earth in 2013.

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That meteorite thankfully landed in a frozen lake almost 80km from the nearest city, but still managed to break thousands of windows as it exploded high above the surface.

While a meteorite the size of 2017 OO1 certainly wouldn’t cause an extinction-level event it would almost certainly have levelled a large district in a city, potentially injuring and killing thousands.

The largest impact event in recorded history was the Tunguska event in 1908, a meteoroid that appears to have exploded some 10-20km in the air causing vast amounts of damage to over 2,000 square kilometres.

With the destructive force of a small nuclear detonation, the air burst flattened over 80,000 trees but thankfully caused no human casualties.

In case you’re worrying about the risk of an asteroid or meteor strike we have some good news.

Earth is struck by asteroids all the time, and almost all the time they either burn up harmlessly in the atmosphere or land on the surface as tiny pieces of rock.

For those large enough to do any serious harm NASA has already set up the asteroid defence program. It is essentially a team of scientists and telescopes being used to detect and then monitor asteroids that have a far higher potential of hitting Earth than 2017 001.

NASA is also working on an asteroid deflection program too which would involve launching a specially designed projectile into space and then firing it at the asteroid in question.

Travelling at nine times the speed of a bullet, the fridge-sized object would hit with such force that it would literally push the object off course.

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