Why We Missed This nearby Mini-Planet for So Long The icy world orbits the sun every 700 years—and is among the 10 biggest unnamed objects in the outer solar system.

Pluto’s family just got a little bit bigger: Astronomers have discovered a new world slightly less than 435 miles (700 kilometers) wide orbiting in the Kuiper belt, the disk of icy bodies beyond Neptune. Provisionally dubbed 2015 RR245 by the International Astronomical Union (IAU) on July 10, the world is smaller than Pluto, Eris, Haumea, Makemake, and Ceres, […]