The hits just keep on coming.
Less than a year after NASA’s Kepler telescope found the first “Tatooine-like” planet, news came this week that the same revolutionary telescope has found not one but two more planets orbiting the same two stars, 4,900 light-years from Earth.
Tatooine is a fictional planet in the Star Wars universe. It was the home of Luke Skywalker and orbited two suns, which could be seen setting in an early scene in “A New Hope.”
This latest discovery, in the constellation Cygnus, is the first time we’ve been proof that more than one planet could exist in orbit around two stars. These circumbinary planets are a testament to the diversity of our universe.
“In contrast to a single planet orbiting a single star, the planet in a circumbinary system must transit a ‘moving target.’ As a consequence, time intervals between the transits and their durations can vary substantially, sometimes short, other times long,” said Jerome Orosz, associate professor of astronomy at San Diego State University and lead author of the paper. “The intervals were the telltale sign these planets are in circumbinary orbits.”
The planets were found in the Kepler-47 system. The stars eclipse each other every 7.5 days from our vantage point. The first one is similar to the sun but only 84 percent as bright. The second is 1/3 the size of the sun and only about 1 percent as bright.
The closest planet, dubbed Kepler-47b, orbits in about 50 days. It’s hot and about three times the size of Earth. The outer planet, Kepler-47c, orbits every 303 days. It is in the “habitable zone,” where liquid water is thought to exist on the surface, but scientists think the planet is a gas giant, and not hospitable to life.
“Unlike our sun, many stars are part of multiple-star systems where two or more stars orbit one another. The question always has been — do they have planets and planetary systems? This Kepler discovery proves that they do,” said William Borucki, Kepler mission principal investigator at NASA’s Ames Research Center in Moffett Field, Calif. “In our search for habitable planets, we have found more opportunities for life to exist.”