This week the Earth had a brush with an asteroid the size of a 20-storey building. Astronomers didn’t notice until two days later.
Our telescopes didn’t pick up the massive space rock as it flew toward the Earth from the direction of the Sun, which effectively blinded them.
It was not till Saturday, July 15, that a telescope in South Africa caught the rock hurtling away from us.
The building-size rock has since been named 2023 NT1 and was observed to be 60 metres in size. It was among the largest to have come so close to Earth in recent times.
An asteroid of that size could have caused significant damage. For perspective, the Chelyabinsk meteoroid from 2013 was only 20 metres wide and injured 1,500 people and damaging buildings when it burst through our atmosphere.
Just two days before NT1 was spotted, the asteroid had swept uncomfortably close to the Earth at 60,000 miles away – only a quarter of the distance between us and the Moon.
The telescope that finally spotted the rogue asteroid was part of the Asteroid Terrestrial-impact Last Alert System (ATLAS), an array of telescopes designed to spot asteroids several days to weeks before any potential impact with Earth.
Over a dozen other telescopes also spotted the rock shortly afterwards, according to the International Astronomical Union’s Minor Planet Center.
While this particular asteroid didn’t pose any danger to Earth, it was a reminder that the Earth’s telescopes could miss potentially dangerous asteroids as many of them fly towards us from the Sun.
The European Space Agency estimates there could be a million asteroids as big as 30 to 100 metres near Earth, with 98.9% of them still undiscovered. A near Earth object is classed as one that passes within 28 million miles of Earth’s orbit.
From its approach last week, scientists have been able to catalogue and predict the asteroid’s movements. That should make it possible to track and spot it next time it comes close to Earth.
In the event that a space object is getting too close for comfort Nasa does have the ability to deflect it. Last year, Nasa crashed a spacecraft into a small asteroid, managing to successfully alter its orbit.
This marked the first time humanity intentionally changed the motion of a celestial object, and the first full-scale demonstration of asteroid deflection technology.
So, in the event an ‘earth-threatening’ asteroid ever does seem to be heading for Earth, then a similar method can be confidently deployed to protect humanity.
But we’ll need to see it coming first.
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