Astronomers find planets locked in 'dance'

PASADENA, Calif., July 29 (UPI) -- Astronomers say they've discovered two giant planets around a distant star doing something they shouldn't be doing -- dancing with each other.

Most planets keep their distance from others circling the same star, as in our solar system, to keep from being affected by each other's gravity, a study to be published in the Astronomical Journal says.

But scientists working at the California Institute of Technology in Pasadena have found two gas giant planets orbiting a massive, dying star that are locked together in an unexpectedly close cosmic dance.

"This new planet pair came in an unexpected package," study author John A. Johnson, a Caltech astronomer, said.

"A planetary system with such closely spaced giant planets would be destroyed quickly if the planets weren't doing such a well synchronized dance," added study co-author Eric Ford of the University of Florida. "This makes it a real puzzle how the planets could have found their rhythm."

The pair tug on each other with powerful gravitational forces 700 times larger than the pull between the Earth and the moon, which causes the tides to rise and fall, the researchers say.