• Pluto

Pluto (Photo : REUTERS)

Two of Pluto's small moons, Nix and Hydra, are driven by the central "binary planet" comprising the planet and its large moon, Charon, causing them to rotate chaotically, a new NASA study revealed.

In the study, NASA astronomers Mark R. Showalter and Douglas P. Hamilton calculated more precisely the orbits of Pluto's four small moons namely Styx, Nix, Kerberos and Hydra. Showalter is from the SETI Institute in Mountain View, Calif., while Hamilton is from the University of Maryland.

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Published in the journal Nature, Showalter and Hamilton's findings revealed that Styx, Nix, Kerberos and Hydra follow near-circular, near-equatorial orbits around the large torques of the Pluto-Charon binary.

Speaking to reporters, Showalter and Hamilton explained why Nix and Hydra seem to be drunk and dancing.

"Imagine for a moment that you're sitting at the center of the Pluto system and you're watching Nix as it goes around you," Showalter explained, RT quoted him as saying. "At first, it wobbles a little bit then it flips over. It is essentially an unpredictable situation."

Hamilton added that two much smaller moons of Pluto, Nix and Hydra, "speed up and slow down, rock their north pole towards the planet and back again and maybe even reverse direction."

Nix and Hydra were discovered in Hubble Space Telescope images in 2005. Kerberos was discovered between the orbits of Nix and Hydra in 2011, and the fifth moon Styx was announced in 2012.

According to Showalter and Hamilton's study, a three-body resonance ties Styx, Nix and Hydra together, which is similar to the Laplace resonance that links Jupiter's moons Europa, Ganymede and Io.