Hubble Finds Two Chaotically Tumbling Pluto Moons
If you lived on one of Pluto’s moons Nix or Hydra, you’d have a hard time setting your alarm clock. That’s because you could not know for sure when, or even in which direction, the sun would rise.
A comprehensive analysis of all available Hubble Space Telescope data shows that two of Pluto’s moons, Nix and Hydra, are wobbling unpredictably. Scientists believe the other two small moons, Kerberos and Styx, are likely in a similar situation, pending further study.
“Hubble has provided a new view of Pluto and its moons revealing a cosmic dance with a chaotic rhythm,” said John Grunsfeld, associate administrator of NASA’s Science Mission Directorate in Washington, D.C. “When the New Horizons spacecraft flies through the Pluto system in July we’ll get a chance to see what these moons look like up close and personal.”
Why the chaos? Because the moons are embedded inside a dynamically shifting gravitational field caused by the system’s two central bodies, Pluto and Charon, whirling about each other. The variable gravitational field induces torques that send the smaller moons tumbling in unpredictable ways. This torque is strengthened by the fact the moons are football shaped rather than spherical.