Astronomers discover 196-foot asteroid with 1-in-83 chance of hitting Earth in 2032

A newly discovered asteroid, designated 2024 YR4, has a 1-in-83 chance of striking Earth in December of 2032. The asteroid is estimated to be 196 feet (60 meters) wide, and it is currently 27 million miles away.

The near-Earth object (NEO) discovered in 2024, which is around half as wide as a football field is long, will make a very close approach to Earth on Dec. 22, 2032. It's estimated to come within around 66,000 miles (106,200 kilometers) of Earth on that day, according to NASA's Center of NEO Studies (CNEOS). However, when orbital uncertainties are considered, that close approach could turn out to be a direct hit on our planet.

Such an impact could cause an explosion in the atmosphere, called an "airburst," or could cause an impact crater when it slams into the ground.

This is enough to see asteroid 2024 YR4 leap to the top of the European Space Agency's NEO impact Risk List and NASA's Sentry Risk Table.

"Odds have slightly increased to 1 in 83," Catalina Sky Survey engineer and asteroid hunter David Rankin wrote on BlueSky. "This is one of the highest probabilities of an impact from a significantly sized rock ever."

Amateur astronomer Tony Dunn shared a simulation of the asteroid approach on his X feed.

The asteroid is rated three on the Torino risk scale, which indicates a close encounter that warrants close attention from astronomers and an over 1% chance of impact.

Where could asteroid 2024 YT4 hit Earth?

Asteroid 2024 YR4 was initially found by a NASA-funded project called ATLAS, using the project's telescope located in Rio Hurtado, Chile. Rankin was then able to recover the asteroid from data collected by the Catalina Sky Survey.

Space.com reached out to Rankin to learn more about asteroid 2024 YR4. His initial message was clear: "People should absolutely not worry about this yet," Rankin told Space.com. "Impact probability is still very low, and the most likely outcome will be a close approaching rock that misses us."

Rankin added that, currently, the "risk corridor" for impact runs from South America across the Atlantic to sub-Saharan Africa.

"It is just important to keep in mind that its orbit is still too uncertain to know if it will hit, and right now, the most likely outcome is a miss," he said. "This impact corridor estimation will eventually go stale with new observations and better orbit calculations."

And, he says, even if 2024 YR4 does hit Earth, this isn't an immediate cause for great concern. There is still a great deal astronomers don't know about this asteroid, and many of these characteristics have a significant influence on the damage it could cause.

"Size and composition are big players in possible damage, along with impact location," Rankin said. "It's hard to constrain size and composition with the current orbital situation, as it's outbound. Typically, the best way to constrain size is with radar observations and those are not possible right now."

He says that astronomers will have a shot at estimating these characteristics in 2028 when 2024 YR4 will make a less risky close approach to Earth, passing within around 5 million miles (8 million kilometers) of our planet.

Astronomers can calculate the size of a distant asteroid based on the amount of light it reflects, or its "absolute magnitude." The problem is, however, that asteroids have varying surface compositions. They can be dark or shiny, and that impacts light-related size estimates.

"Based on the calculated absolute magnitude, it's about 196 feet (60 meters) wide, but that assumes a certain surface reflectivity," Rankin said. "If the asteroid has a darker surface, that number is too small; if it has a more reflective surface, that number is too high."

That is why they need that radar data to be more sure of the size of asteroid 2024 YR4.

What damage could asteroid 2024 YT4 cause?

Let's say the data we have on asteroid 2024 YT4 is currently correct. What kind of risk does an impact by this asteroid pose to Earth?

"It is likely around the same size as the 1908 Tunguska rock or the Meteor Crater rock," Rankin said. "So, while impact effects would be more localized than regional, it certainly has the potential to do serious damage to the area it hits."

Tunguska is currently the largest recorded asteroid strike event in human history, though we know of many greater impacts in prehistoric times. The most notable of these is the catastrophic Chicxulub impact, which happened around 66 million years ago and wiped out two-thirds of life on Earth and ended the reign of the dinosaurs.

Tunguska was less dramatic, but was no slouch in terms of damage. Releasing the same energy as the detonation of up to 50 million tons of TNT when it exploded in the atmosphere over a sparsely populated region of Russia, the blast flattened an estimated 80 million trees over an area of 830 square miles ( 2,150 square km) and possibly killed three people.

"If [asteroid 2024 YT4] is made of stony material, it could cause a significant air burst and fireball reaching the ground," Rankin said. "If made of iron, it will punch right through the atmosphere with little trouble and make an impact crater. This is why understanding not just the orbit but also the composition and size are so critical."

Rankin and astronomers across the globe will now endeavor to learn as much as they can about asteroid 2024 YT4 before 2032.

"We will have the opportunity to continue to track this rock through February with 8-meter class telescopes, which we plan on doing at Catalina Sky Survey," Rankin said. "It is possible that even after February, we will not know for sure if it will hit or miss in 2032. We should be able to determine that better by 2028, when it should be visible again."

Editors Note: Impact path was changed from "South Africa" to "sub-Saharan Africa" to reflect updated data.