Name the second-largest dwarf planet known in the Solar System
It was discovered on the 5th of January, 2005
According to Wikipedia, Eris is the most massive dwarf planet known in the Solar System. It is also the largest known body in the Solar System not visited by a spacecraft ever. This dwarf planet is more massive than Pluto, yet Pluto is said to be larger by volume. When discovered, Eris was thought to be larger than Pluto, so it was initially described as the tenth planet of our planetary system.