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Today in History: Hubble Reveals Pluto's New Moons Nix, Hydra

By Drooid · Oct 31, 2026 · How we work

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Astronomers announced on Oct. 31, 2005 that Hubble images taken five months earlier revealed two new Pluto moons—Nix and Hydra. The 49-km and 51-km bodies orbit between Styx and Kerberos and beyond Kerberos, respectively, making them Pluto’s third and fifth satellites. Their discovery expanded the dwarf planet’s known satellite system.

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Astronomers announced on Oct. 31, 2005 that Hubble images taken five months earlier revealed two new Pluto moons—Nix and Hydra. The 49-km and 51-km bodies orbit between Styx and Kerberos and beyond Kerberos, respectively, making them Pluto’s third and fifth satellites. Their discovery expanded the dwarf planet’s known satellite system.