Planet killer asteroid ‘the size of Mount Everest’ to skim past Earth

Buckle up, because a mountain-sized ‘planet killer’ asteroid will fly past Earth on Thursday – quickly followed by another that was only spotted a few weeks ago.

The big one, the catchily-named 2011 asteroid (415029) 2011 UL21, is a monstrous 2,310 metres wide, bigger than 99% of all other known near-Earth objects (NEOs) and bigger than any mountain in the UK. 

You might hear it is similar in size to Mount Everest, but given the world’s tallest peak is almost nine kilometres high, this generous comparison appears to be in reference to the width of the summit.

And while it is big enough to fall into the ‘planet killer’ category, it is only a fraction of the size of the Chicxulub asteroid thought to have wiped out the dinosaurs, estimated at around 10 kilometres, or six miles, wide.

Unlike most other NEOs, it isn’t orbiting the Sun on a similar plane to the planets, but instead is at a steep angle – possibly due to the effects of Jupiter’s massive gravitational effects. As noted by the European Space Agency (ESA), Jupiter has been known to knock previously-safe asteroids towards Earth.

Thankfully however, this time, (415029) 2011 UL21 won’t be getting too close, with a nice buffer of about four million miles between Earth and the space rock.

But on Saturday, another asteroid will whizz by much closer – less than the distance between Earth and the Moon.

Asteroid 2024 MK was only discovered on June 16, and will pass within 180,200 miles of the planet, around 75% of the distance to the Moon.

While closer, the new discovery is significantly smaller, as only around 120 and 260 metres wide – but could still do plenty of damage were it to hit.

Dr Greg Brown, astronomer at the Royal Greenwich Observatory, said: ‘This week, two asteroids will pass somewhat nearby to the Earth. For small asteroids this is a very common occurrence, with close passes dozens of times a month. 

‘However, these two asteroids are somewhat larger than we normally expect.

‘While neither asteroid poses a threat to Earth, 2024 MK was discovered less than two weeks before its projected close approach. It is also thought to be considerably larger than the asteroid that caused the Tunguska event which caused devastation across a 2,000 square kilometre region of – thankfully uninhabited – Siberian countryside in 1908.

‘While even 2024 MK is far smaller than any asteroid that could cause an impact that affects the world at large, if it, or another similar asteroid, struck the Earth, it would nonetheless be extremely hazardous to the local region. 

‘This makes clear how important it is that we continue to invest in improved ways of detecting near-Earth objects well ahead of any possible impact.’

All across the world, astronomers are observing the night sky for potentially hazardous asteroids, while in 2028, Nasa is due to launch its new Near-Earth Object surveyor mission, a powerful infrared telescope designed to seek out hazardous space rocks.

For now, the two asteroids zipping by will do so without any disastrous consequences for Earth – and in fact, give Sunday’s International Asteroid Day a bit of extra pop.