Scientists believe a ‘house-sized’ asteroid originally thought to have a chance of hitting Earth now has double the chance of smashing into the Moon. Researchers have managed to work out the shape of the 2024 YR4 asteroid, saying it is shaped like a hockey puck.
Astronomers have also deduced the asteroid’s origin, which was first detected in December. Initially, it was believed the ‘city-killer‘ asteroid had a chance of crashing into Earth on December 22, 2032. But further analysis dropped the Earth impact probability below 1% in late February, with the asteroid now no longer deemed a risk.
But, experts at NASA’s Center for Near Earth Object Studies at the agency’s Jet Propulsion Laboratory have updated 2024 YR4’s chance of hitting the Moon – increasing it from 1.7% to 3.8%. The updated chances are based on James Webb Telescope data and observations from ground-based telescopes.
Using observations from the Gemini South telescope in Chile, operated by NSF NOIRLab, researchers have now created a new 3D representation of 2024 YR4. The team of astronomers were led by Bryce Bolin, lead author of the paper which appeared in The Astrophysical Journal Letters.
The team used the telescope to capture images of the asteroid in multiple different wavelengths. Detailed analysis of the asteroid’s lightcurve, its pattern of light and output in time, allowed the team to work out its composition, orbital characteristics and 3D shape.
The team determined that the unusually-shaped space rock is one of the largest object in recent history that could impact the Moon. It likely originates from the main asteroid belt, with its reflective pattern suggesting a diameter of around 30-65 metres.
Analysis also revealed the asteroid has a rapid rotation period of around one rotation every 20 minutes, as well as an unusual hockey-puck-like shape. Bryce Bolin said: “This find was rather unexpected since most asteroids are thought to be shaped like potatoes or toy tops rather than flat disks.”
Based on the orbital characteristics, the team determined that 2024 YR4 most likely originated from the main asteroid belt. They also predicted a high probability of being perturbed into its current near-Earth orbit by gravitational interactions with Jupiter.
Its retrograde spin direction suggests it may have migrated inward from the central Main Belt region, adding to our understanding of how small asteroids evolve and reach Earth-crossing trajectories.
Mr Bolin said: “We are a bit surprised about its origin in the central main asteroid belt, which is a location in the asteroid belt that we did not think many Earth-crossing asteroids could originate from.
“Our observations with Gemini South provided a crucial piece of the puzzle in determining 2024 YR4’s characteristics.
“Studying this asteroid was vitally important in understanding the population of Earth crossers that have the potential to be Earth impactors and are poorly understood.”
Martin Still, NSF program director for the International Gemini Observatory, added: “Understanding the properties and origins of near-Earth asteroids is proving critical for understanding the risk of collisions between our planet and major bodies in crossing orbits. The Gemini telescopes and other astronomical observatories are vital tools for planetary defence.”
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