On this date, Jan. 6, 1969, the Soviet Union launched the Venera 5 spacecraft, which was part of an ongoing mission to explore Earth’s sister planet, Venus. Venera 5 successfully entered Venus’ ...

Astronomers believe that Planet Nine could be 5-7 times the size of Earth and situated more than 200 times farther from the sun than our planet. It is believed to orbit the Sun in 10,000 to 20,000 ...

Eris was discovered. It was considered the largest known dwarf planet in the solar system until a year later when Pluto was downgraded from being a planet.