NASA's Webb captures first glimpse of asteroid once seen as earth's biggest threat

Yahoo

05-04-2025

NASA's James Webb Space Telescope has captured stunning new images of an asteroid that was once ranked as the biggest threat to Earth.
Earlier this year, the asteroid 2024 YR4 shot to the top of the planetary defense watchlist after it was predicted to have a 3 percent chance of hitting Earth in 2032.
According to reports, there is a slight chance that the space rock, which swings in our direction every four years, could hit the Moon in the coming decade.
The asteroid first drew the attention of NASA and astronomers when it appeared on the U.S. space agency's Sentry Impact Risk Table, which tracks asteroids with a non-zero probability of striking Earth.
For a time, it was the only object among more than 37,000 known large space rocks with any realistic chance of impact, with its probability peaking at a record 3.1%.
However, by late February, more precise observations allowed scientists to refine their calculations, reducing the odds of an Earth impact to virtually zero.
NASA and the European Space Agency have released images of the asteroid, appearing as a faint, fuzzy dot.
Webb—humanity's most powerful eye in space—has now confirmed that the asteroid measures between 174 and 220 feet (53–67 meters), about the size of a 10-story building.
'The previous size estimate of 131–295 feet (40–90 meters) was derived from visible light measurements from ground-based telescopes,' NASA said in a release.
The space rock is the smallest object ever observed by the largest and most powerful space telescope.
After mid-April, asteroid 2024 YR4 will move too far and become too faint for ground-based telescopes to track.
However, Webb is set to observe it again in late April or early May.
Johns Hopkins University astronomer Andrew Rivkin, who helped with the observations, said the observations served as 'invaluable' practice for other asteroids that may threaten the Earth.
All this 'gives us a window to understand what other objects the size of 2024 YR4 are like, including the next one that might be heading our way,' he said.
While Earth is no longer under threat from 2024 YR4, the Moon still faces a small possibility of impact.
Following Webb's observations, NASA's Center for Near Earth Object Studies updated the asteroid's chances of hitting the Moon on December 22, 2032, raising the probability from 1.7% in February to 3.8%.
Even if an impact were to occur, NASA assures it would not alter the Moon's orbit around Earth.
Asteroid 2024 YR4 was first detected by the NASA-funded Asteroid Terrestrial-impact Last Alert System (ATLAS) in Chile and reported to the Minor Planet Center on December 27, 2024.
Despite the reduced threat, astronomers are eager to continue monitoring 2024 YR4.
Along with its larger counterpart, Apophis—another once-concerning asteroid—YR4 provides a valuable opportunity to study these imposing space rocks.
Scientists believe such research could help space agencies refine planetary defense strategies in case a future asteroid ever poses a real danger to Earth.