A quiet messenger from the farthest reaches of the Milky Way is making its last, dramatic appearance on this day, December 19, 2025. The interstellar comet 3I/ATLAS, which is a frozen remnant from the orbit of a faraway, alien sun, is now getting as close to Earth as it can get.
People think the comet is between 440 meters and 3.5 miles (5.6 km) wide, which would make it the biggest object ever seen in space. It's a scary thought that this is the last time any human eyes—or even our most powerful sensors—will ever see it before it disappears into the infinite void and never comes back.
