MUCH BIGGER THAN HAMNER-BROWN: ‘Megacomet’ Bernardinelli-Berstein is largest ever seen, Hubble telescope confirms: The icy nucleus stretches about 80 miles (129 kilometers) across. “This comet, being so far from Earth and originating in the farthest-flung reaches of our solar system, is thought to travel on a 3-million-year-long elliptical orbit around the sun. Scientists think that it might travel about half a light-year away from the sun in the farthest parts of its orbit.”