On July 25, a huge asteroid which is roughly the size of a football pitch, skimmed Earth, and scientists were unaware it was coming. The asteroid in question is known as ‘2019 OK’ and when it was first discovered, it was not classed as a near-Earth asteroid. However, the European Space Agency (ESA) confirmed that scientists had only noticed it was travelling near Earth “just days” before it whizzed past as a distance of 65,000 kilometres – one fifth of the distance to the Moon.
The ESA stated: “The 100 m-wide asteroid dubbed ‘2019 OK’ was detected just days before it passed Earth, although archival records from sky surveys show it had previously been observed but wasn’t recognised as a near-Earth asteroid.
“We know of, and are tracking, thousands of asteroids in the Solar System, so why was this one discovered so late?
“Unfortunately, there is currently no single obvious reason, apart from its slow motion in the sky before close approach.
“2019 OK also travels in a highly elliptical orbit, taking it from within the orbit of Venus to well beyond that of Mars.
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“This means the time it spends near Earth and is detectable with current telescope capabilities is relatively short.
“ESA, NASA and other agencies and organisations around the globe – professional and amateur – discover new asteroids every day.
“This work constantly increases our understanding of the number, distribution and movement of orbiting rocky bodies.”
The ESA finally managed to discovered 2019 OK just a day before its approach after it requested that the International Scientific Optical Network (ISON) take images of the space rock.
The ISON is an international collaboration of 30 telescopes in ten countries.
Thanks to its observations, the ESA managed to pinpoint its location to within a kilometre.
Marco Micheli from ESA’s Near-Earth Object Coordination Centre, said: “With the ISON observations we were able to determine the distance of the close approach incredibly accurately.
“In fact, with a combination of observations from across the globe, the distance is now known to better than one kilometre!”
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While asteroid impacts on the scale of the one which struck Earth 65 million years ago, ending the dinosaurs reign, are exceedingly rare, they are still possible, experts warn.
And even ones on a much smaller scale still have the potential to cause huge damage to our planet.
Scientists often point to two relatively recent incidents in which the asteroids were not detected which prove Earth is still vulnerable to asteroid impacts.
In 1908, a small asteroid exploded over Siberia’s Tunguska which ruined woodlands across 800 miles.
In 2013, a 20 metre meteor exploded over Chelyabinsk, Russia, which smashed windows and caused injuries to more than 1,000 people.
Experts had not anticipated either incident, leading to fears that Earth could be surprised by a more devastating asteroid strike in the future.
In an article for the Conversation, Jonti Horner, Professor of astrophysics at University of Southern Queensland, previously said: “We’re still trying to work out how often events like this happen.
“Our information on the frequency of the larger impacts is pretty limited, so estimates can vary dramatically.
“Typically, people argue that Tunguska-sized impacts happen every few hundred years, but that’s just based on a sample of one event.
“The truth is, we don’t really know.”