A research team led by astronomers at the University of Washington and Harvard University has discovered a bigger version of Earth locked in an orbital tug-of-war with a much larger, Neptune-sized planet as they orbit very close to each other around the same star about 1,200 light years from Earth.
The planets occupy nearly the same orbital plane and on their closest approach come within about 1.2 million miles of each other – just five times the Earth-moon distance and about 20 times closer to one another than any two planets in our solar system.
But the timing of their orbits means they’ll never collide, said Eric Agol, a UW astronomy professor and co-lead author of a paper documenting the discovery published June 21 by Science Express, the online edition of the journal Science.
“These are the closest two planets to one another that have ever been found,” Agol said. “The bigger planet is pushing the smaller planet around more, so the smaller planet is harder to find.”
Orbiting a star in the Cygnus constellation referred to as Kepler-36a, the planets are designated Kepler-36b and Kepler-36c. Planet b is a rocky planet like Earth, though 4.5 times more massive and with a radius 1.5 times greater. Kepler-36c, which could be either gaseous like Jupiter or watery, is 8.1 times more massive than Earth and has a radius 3.7 times greater.