Pluto’s outer moons are continuously toppled and turned as they battle the joint gravitational forces of their parent planet and its primary moon Charon, a study published on Wednesday showed.
“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.
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)