The chance of asteroid 2024 YR4 striking Earth has been reduced to almost zero after new observations dramatically shrunk the “uncertainty window,” according to the European Space Agency.
This image made available by University of Hawaii's asteroid impact alert system shows the motion of ... [+]
The asteroid had been thought to be potentially on a collision course with Earth, with a chance of its striking the planet on Dec. 22, 2032, along a “risk corridor” stretching from the eastern Pacific Ocean through northern South America, the Atlantic Ocean, Africa, the Arabian Sea and South Asia.
Using limited observational data, the International Asteroid Warning Network published a warning on Jan. 29, 2025, with NASA JPL Center for NEO Studies and ESA NearEarth Objects Coordination Center calculating that 2024 YR4 had a 1.3% chance of impacting Earth.
On Feb. 18, the asteroid’s impact probability was increased to 3.1%, the highest ever recorded for an object of this size. The following day, it was reduced to 1.5%, according to NASA.
The latest data, published by ESA, has the chance of impact now at 0.002% — or 1 in 50,000 — on Feb. 24, 2025.
The asteroid had been classified as level 3 (yellow, “meriting attention by astronomers”) on a scale of 10 on the Torino Impact Hazard Scale, a tool for categorizing potential Earth impact events. It fell to level 1 (green, “normal”) on Feb. 20 and has now been labeled level 0 (white, “no hazard”).
“Asteroid 2024 YR4 has now been reassigned to Torino Scale Level Zero as additional tracking of its orbital path reduces its possibility of intersecting the Earth to below the 1-in-1000 threshold established for downgrading to Level 0,” said Richard Binzel, professor of planetary science at the Massachusetts Institute of Technology and inventor of the Torino Scale, in an email, which ended with the sign-off “That’s Zero Folks!” Further observations of the asteroid's orbit had been expected to result in it being declared harmless.
The James Webb Space Telescope is scheduled to spend four hours observing 2024 YR4 during “director’s discretionary time” in early March and May. The asteroid will then be hidden from view of Earth until June 2028. Webb’s MIRI instrument — which sees in infrared light (heat) — will primarily be used to get a much more precise estimate of the asteroid’s size.
2024 YR4 was discovered on Dec. 27, 2024, by the Asteroid Terrestrial-impact Last Alert System in Chile. Initially, it was thought that the diameter would be approximately 130 to 300 feet (40 to 90 meters), but recent observations have reduced its size to about 165 feet (50 meters) in diameter.
2024 YR4 orbits the sun every four Earth years, so it passes relatively close to Earth once every four years. It's next expected to pass relatively close to Earth in December 2028. 2024 YR4 is one of about 20,000 Apollo-type asteroids that orbit the sun from about the same distance as Earth, so it is a potential threat.
“Given that the probability of the likely impact has been re-evaluated, it’s important to recognize that 2024 YR4 doesn’t pose an existential threat to humanity,” said Franck Marchis, SETI astronomer and co-founder of smart telescope maker Unistellar, in an email.