NASA’s Hubble Space Telescope has shown that two of Pluto’s moons, Nix and Hydra, wobble unpredictably.
John Grunsfeld, associate administrator of NASA’s Science Mission Directorate, said that Hubble has provided a new view of Pluto and its moons, revealing a cosmic dance with a chaotic rhythm and added that when the New Horizons spacecraft flies through the Pluto system in July they’ll get a chance to see what these moons look like up close and personal.
The moons wobble because they’re embedded in a gravitational field that shifts constantly. This shift is created by the double planet system of Pluto and Charon as they whirl about each other.
Pluto and Charon are called a double planet because they share a common center of gravity located in the space between the bodies. Their variable gravitational field sends the smaller moons tumbling erratically. The effect is strengthened by the football-like, rather than spherical, shape of the moons.
Scientists believe it is likely that Pluto’s other two moons, Kerberos and Styx, are in a similar situation.
Researcher Mark Showalter, who found the results, added that their research provides important new constraints on the sequence of events that led to the formation of the system.
Showalter also found three of Pluto’s moons are presently locked together in resonance, meaning there is a precise ratio for their orbital periods.
Hubble data also reveal the moon Kerberos is as dark as a charcoal briquette, while the other frozen moons are as bright as sand. It was predicted that dust blasted off the moons by meteorite impacts should coat all the moons, giving their surfaces a homogenous look, which makes Kerberos’ coloring very surprising.
The study appears in the journal Nature.