Solar System Chatter

Pluto’s Wobbly Moons

NASA, ESA, M. Showalter (SETI Institute), and G. Bacon (STScI)
NASA, ESA, M. Showalter (SETI Institute), and G. Bacon (STScI)
Hubble Space Telescope observations of Pluto show that two of the planet’s small moons, Nix and Hydra, are tumbling chaotically as they orbit the double planet (Pluto and its large moon Charon). Most solar system objects rotate predictably on an axis, and have a regular day/night cycle. These have no pattern whatsoever. In fact, said astronomer Mark Showalter of the SETI Institute, if you lived on one of these small, football-shaped moons, “You would literally not know if the sun is coming up tomorrow.” Next month the New Horizons spacecraft will get close-up pictures of Nix and Hydra that are 50 to 100 pixels across, enough to make out large surface features. Here’s an artist’s impression of Nix tumbling around Pluto.

Heather Goss is the Departments Editor at Air & Space.

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