NASA finds goofy orbits for Pluto’s four small moons

NASA scientists revealed new data Wednesday about the five moons orbiting the dwarf planet Pluto, where the New Horizons space probe is set to arrive on July 14 after the $700 million craft’s 3 billion mile, nine-year journey.

Scientists used New Horizons and the Hubble Space Telescope to combine images of Pluto — as well as its dwarf planet moon, Charon, and tiny moons Styx, Nix, Hydra and Kerberos — to reveal odd rhythmic gyrations of the six distant objects in a dance unlike anything else in our solar system. The four moons orbit around Pluto and Charon, which orbit each other like two ends of a dumbbell, scientists said.

“We are learning chaos may be a common trait of binary systems,” said Douglas Hamilton, a professor of astronomy at the University of Maryland who was involved in the study. “It might even have consequences for life on planets if found in such systems.” The scientists’ findings are set for publication in the June 4 edition of the scientific journal Nature.

In a binary system, two relatively close celestial bodies’ gravitational fields become locked, and they orbit each other.

What makes the Pluto situation so odd is that there’s a double set of moon dances going on. First, Pluto and Charon are locked together in their own waltz as a binary system, with a gravitational rod connecting them, said study author Mark Showalter of the SETI Institute in California. It’s the solar system’s only binary planet system, even though Pluto and Charon aren’t technically planets, he said.

The four tiny moons circle the Pluto-Charon combo, wobbling a bit when they go closer to either Pluto or Charon, pulled by the gravity of the two bigger objects.

“It’s pretty darn weird,” Showalter said, adding that a person on any one of the moons “would literally not know if the sun is coming up tomorrow.”  

Some scientists believe that Pluto and its moons came from an ancient collision that broke one object into parts that later became Pluto, Charon and the four moons. 

The four moons orbit Pluto-Charon in a precise, rhythmic way but with a twist: They also interact through gravity when they near each other. So it seems they all dance to one overarching “beat” but not quite in the same way, with each apparently doing its own thing to some extent, said planetary scientist Heidi Hammel of the Association of Universities for Research in Astronomy.

Hammel, who was not part of the Pluto-Charon study, praised it as giving a glimpse of what might be happening in other distant star systems that have planets revolving around two stars — like Tatooine in the “Star Wars” films.

After its Pluto flyby, the New Horizons space probe is expected to leave the solar system.

Al Jazeera and The Associated Press

Correction: An earlier version of this article listed the cost of the mission at $700 billion. It is $700 million.