A team of astronomers has determined the shape of asteroid 2024 YR4, which could collide with the Moon. (Image credit: NOIRLab/NSF/AURA/R. Proctor)
Scientists have revealed the unusual shape of a large asteroid that could hit the Moon in 2032, according to a new study.
Asteroid 2024 YR4 gained significant attention earlier this year when NASA reported the possibility of it hitting Earth. The risk of an Earth impact has since been reduced to zero, but there is still a small chance that 2024 YR4 could hit the Moon in 2032 — a 3.8% chance as of early April.
Recently, a team of astronomers conducted a more detailed study of the asteroid using the Gemini South telescope in Chile. The researchers found that 2024 YR4 likely originated in the asteroid belt between Mars and Jupiter and has an unusually flat, disk-shaped shape reminiscent of a hockey puck, according to a statement released by the National Science Foundation's National Optical-Infrared Astronomy Research Laboratory (NOIRLab).
“This discovery was quite surprising, since most asteroids are thought to be shaped like potatoes or spinning tops, rather than flat disks,” said lead study author Bryce Bolin, a research scientist at Eureka Scientific, a California-based astrophysics and astronomy research corporation.
The researchers have posted their results on the arXiv preprint database and will soon publish them in The Astrophysical Journal Letters.
Astronomers discovered asteroid 2024 YR4 in December 2024, which is where it got its name. In February, the odds of 2024 YR4 colliding with Earth in 2032 rose to 1 in 32, or 3.1%, the highest impact odds ever recorded by NASA for an object the size of 2024 YR4 or larger.
However, astronomers always assumed that the threat level would decrease as they got more data on 2024 YR4's trajectory. Within a few days, the probability plummeted to zero, and at the time of writing, the probability of an impact with Earth in 2032 is 0.00078%. Still, the risk to the Moon remains – although the asteroid would not be able to significantly damage the Moon even if it did hit.
As part of the new study, the scientists took images of the celestial body at different wavelengths of light. The team used a model of 2024 YR4's light output over time, known as a light curve, to analyze the asteroid's shape, composition, and orbital characteristics, according to a statement.
From the asteroid's reflection model, the researchers concluded that 2024 YR4 is likely an S-type asteroid, meaning it is rich in silicates, a class of minerals that includes quartz. The team also determined that the asteroid rotates very quickly, about every 20 minutes, and estimated its size to be between 98 and 213 feet (30 and 65 meters) wide, according to the study.
Researchers have been trying to pinpoint the size of 2024 YR4 since its discovery, and this latest approximation is similar to previous estimates. The latest data from the James Webb Space Telescope suggests it may be slightly larger, between 174 and 220 feet (53 and 67 meters), Live Science previously reported.
According to the statement, 2024 YR4 is one of the largest objects in recent history that could impact the Moon. When the likelihood of 2024 YR4 colliding with Earth was growing, it was called a potential “city killer” because it was large enough to wipe out a major city.
While unlikely, a lunar impact would reportedly provide researchers with a unique opportunity to study how the size of an asteroid relates to the size of the crater it creates.
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