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 "It as if Pluto and Charon are two weights at the end of a
dumbbell, two very unbalanced weights, and that dumbbell is
rotating. The four other moons are responding to the gravity fields
of both objects,” astronomer Mark Showalter told reporters on a
conference call.
The study, published in this week’s journal Nature, should help
scientists figure out how Pluto and its entourage of moons formed
and provide insight into the solar system’s origins.
NASA’s New Horizon’s spacecraft is due to fly within about 7,750
(12,500 km) of Pluto on July 14.
A computer simulation of Pluto's moon Nix, based on images taken by
the Hubble Space Telescope, showed the body tumbling, wobbling and
flipping over.
 “It’s a very strange world. You literally would not know if the sun
is coming up tomorrow. The sun might rise in the west and set in the
east … or the north. If you have real estate on the north pole of
Nix, you might suddenly discover one day that you’re on the south
pole instead,” said Showalter.
The study was conducted by Showalter, who is with the SETI Institute
in Mountain View, California, and Douglas Hamilton of the University
of Maryland.
Pluto was once considered the ninth planet in the solar system, but
it was striped of that title in 2006 after astronomers discovered
several similar icy bodies in the Kuiper Belt region, about 50 times
farther away from the sun than Earth.
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Even before its demotion, Pluto was a planetary oddball, just 1,460
miles (2,350 km) in diameter, which is smaller than Earth’s moon,
and circling the sun in a tilted, oval-shaped orbit that
occasionally reaches inside neighbor Neptune’s path.
Scientists suspect Pluto, Charon and its four small moons, all
discovered in Hubble images after New Horizons launched, formed
after an ancient collision of two icy bodies.
That theory will be tested with the new evidence of the tumbling,
wobbly moons, and observations by New Horizon.
New Horizons, launched in January 2006, will be the first spacecraft
to visit Pluto. It will then head into the Kuiper Belt for a
possible flyby of a second object in 2019.
(Reporting by Irene Klotz)
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