On 2 April 2052, a dangerous asteroid will enter the atmosphere and threaten the Earth, just in time for worldwide Asteroid Day. 

With one of the most sensitive telescopes in the world, ESA's asteroid team and the ESO's experts have officially removed asteroid 2021 QM1 from the asteroid risk list. This was a result of skilled observations and analysis of the faintest asteroid ever discovered.

Since Asteroid Day Live 2022 is scheduled for 30 June, we can confidently predict the most dangerous asteroid in human history in the next century won't strike.

A new comet has been discovered by observation at the Mount Lemmon Observatory, which is located north of Tucson, Arizona, on 28 August 2021. 

There was nothing particularly unusual about the discovery - a dozen or so new near-Earth asteroid discoveries are made every night, so it is hardly shocking at the time. 

In the days to come, follow-up observations from telescopic observatories around the world became more and more common, but they started telling a different, more alarming story.

Richard Moss, Head of Planetary Defence at the European Space Agency, said these early observations provided more insight into the asteroid’s path. The asteroid could end up dangerously close to Earth in 2052, based on its future path around the Sun. Observations of the asteroid increased that risk.”

An asteroid's orbit can be calculated from a few nights of observations, which is why asteroids end up on the ESA's risk list soon after they are detected and are then removed once more information is gathered, uncertainties decrease, and the asteroid is deemed innocuous. This was not possible on this occasion.

Unfortunate alignment of the stars

An imperfect cosmic alignment brought the asteroid nearer to the Sun as seen from Earth, and for months it was visible only because of the star's brilliant glare. 'It was just a matter of waiting,' explained Marco Micheli, Astronomer at ESA's Near-Earth Object Coordination Centre.

'However, we knew 2021 QM1 was also moving away from Earth in its current orbit, which meant by the time it passed out of the Sun's glare, it could be too faint to detect.' In the meantime, they prepared.

One of Earth's most powerful telescopes will be available to you as a priority, VLT was primed and ready for use by the European Southern Observatory. If and when the weather permits, ESO's VLT will focus its 8m mirror on the asteroid as soon as the 50-meter rock edges out from the sun.

Olivier Hainaut, Astronomer at ESO, explained that we had a brief window of opportunity to spot our asteroid.

The Milky Way was visible in the background as it passed through the region of the sky in front of it. It would be difficult to find our tiny, faint, receding asteroid despite thousands of stars surrounding it. Observations of asteroids would turn out to be some of the trickiest ever'.

Asteroid observed at its faintest

A series of new images were taken by ESO's VLT on 24 May. When Olivier and Marco received the data, they began to process it, stacking subsequent observations on top of each other and removing any background stars that were detected. 

As a result? The faintest asteroid on record was found. Astronomers use the magnitude scale to describe lights in the sky, and 2021 QM1 had a magnitude of 27 on that scale. The faintest star visible from a dark spot is 250 million times fainter than 2021 QM1.

Olivier and Marco both knew this asteroid was ours due to its location. Using these observations, we were able to refine 2052 QM1's path, effectively removing it from the ESA's risk list. Still, there are another 1377 targets.

The Solar System has more than one million asteroids, almost 30000 of which pass near Earth, with many more expected to exist. NASA's Planetary Defence Office, NEOCC, and astronomers from around the world are looking up for signs of asteroid collisions and sharing information about them.

Livestream of Asteroid Day 30 June

Experts around the world are worried about asteroid impacts. Have you ever tracked a potentially dangerous asteroid? Asteroid Day will be celebrated live on 30 June at 10:30 CEST if you tune in to ESA WebTV and AsteroidDay.org.

Observed on 30 June every year, Asteroids Day is a United Nations-sanctioned day to raise awareness of asteroid hazards. The event is returning to Luxembourg for the first time after spending the last two years exclusively online. 

Astroid experts from across Europe and throughout the world will take part in a packed four-hour live programme of panel discussions and one-on-one interviews in Rome.