Fearless James Webb Telescope Stares Down "City Killer" Asteroid That Had Been Feared to Strike Earth

That "city-killer" asteroid may no longer be projected to strike Earth any time soon, but scientists are still keeping close tabs on it. Using the mighty James Webb Space Telescope, astronomers have imaged the once-menacing space rock, dubbed 2024 YR4, in infrared light, providing our best estimate yet of its true size. It's also a convincing demonstration of the telescope's usefulness in assessing the hazards of near-Earth asteroids in the future. Previously, our ground-based glances at 2024 YR4 in visible light had suggested that it could be as long as nearly 300 feet. Now, the latest observations reveal that it's somewhat smaller, between 174 to 220 feet in stature — or about the size of a 10-story building, according to NASA. "This is the smallest object targeted by the mission to date, and one of the smallest objects to have its size directly measured," Andy Rivkin, principal investigator of the Webb telescope's Director's Discretionary Time program, said in a statement. "Whil ... Read full article.