Asteroid that may collide with Earth discovered, chances of collision are 1 in 77

In December 2024, astronomers using a Chilean telescope, part of the Asteroid Terrestrial Impact Last Alert System (ATLAS), discovered an asteroid called 2024 YR4 that may be on a collision course with Earth. Jonty Horner, a professor of astrophysics at the University of Southern Queensland, explains what we know about 2024 YR4 and its chances of hitting Earth.

Sentry: Earth Impact Monitoring
https://cneos.jpl.nasa.gov/sentry/details.html#?des=2024%20YR4

Astronomers have spied an asteroid that may be heading for Earth. Here's what we know so far
https://theconversation.com/astronomers-have-spied-an-asteroid-that-may-be-heading-for-earth-heres-what-we-know-so-far-248753

2024 YR4 was discovered on December 27, 2024, just a few days after passing relatively close to Earth. Astronomers have been closely monitoring 2024 YR4 for about a month since its discovery. As a result, as of February 2025, 2024 YR4 is on an orbit that is moving away from Earth again, and by April it is expected to move out of sight of even the world's largest telescopes.

The movie below shows the observation results of 2024 YR4 taken with the European Southern Observatory (ESO) Very Large Telescope in January 2025. The object of observation is fixed in the center of the frame and the background stars are adjusted to appear to move, so the small stationary dot in the center of the movie is 2024 YR4.

Near Earth Asteroid 2024 YR4 observed with the VLT - YouTube


From observations of about a month, astronomers have estimated the future movement of 2024 YR4. According to the estimated orbit, it is clear that 2024 YR4 will approach Earth quite closely on December 22, 2032, and there is a possibility of a collision. Sentry , an automated asteroid collision prediction system operated by the Center for Near Earth Object Studies at NASA's Jet Propulsion Laboratory, estimates the position of 2024 YR4 when it approaches Earth with an error of about 100,000 km, and the Earth, which has a diameter of about 12,000 km, fits completely within that estimated area.

According to calculations as of February 2025, the probability of 2024 YR4 colliding with the Earth is approximately 1 in 77. The exact size of 2024 YR4 is unknown, and estimates based on its brightness suggest that it has a diameter of between 40m and 100m. When considering 'what would happen if 2024 YR4 collided with the Earth,' it is important to consider not only the size of 2024 YR4, but also what the asteroid is made of. The most likely scenario is that it is a chunk of rock, which would explode in the atmosphere and send shock waves to hit the Earth, causing damage that could blow away an area the size of a city, similar to the Tunguska explosion in 1908. Another pattern that is unlikely but cannot be ruled out is that of an asteroid made of metal, which would pass through the atmosphere almost unscathed and would create a crater over 1km in diameter and hundreds of meters deep if it collided with land.

After 2024 YR4 leaves Earth in 2025, it is predicted to approach Earth again to a position of about 8 million km from Earth in December 2028, so astronomers are preparing to observe the size and shape of the asteroid in more detail at that time. According to Horner, the observations in 2028 are expected to allow very accurate predictions of the position of 2024 YR4 in 2032, so it is possible to predict within a range of tens of kilometers whether it will actually collide with Earth and where on Earth it will be if it does.

Horner said, 'Over the past few years, we've identified 11 asteroids that could potentially hit Earth. In each case, we predicted where the asteroid would hit and observed the results. 2024 YR4 is one of those asteroids, which has some probability of impact and moderate damage, but not enough to affect areas outside the immediate impact area. We've also gotten better at deflecting potentially threatening asteroids, like NASA's DART , which has demonstrated how to change the trajectory of an asteroid. So there's no need to panic, just wait and see for more information.'