September 19, 2011 — There are double-decker buses and double rainbows. And now there is proof of a world with a double sunset.
NASA's Kepler mission recently made the first clear detection of a circumbinary planet - a planet orbiting two stars - 200 light-years from Earth. The planet is cold, gaseous, and not thought to harbor life, but its discovery demonstrates the diversity of planets in our galaxy.
Previous research has hinted at the existence of circumbinary planets, but confirmation proved elusive. Kepler detected such a planet, known as Kepler-16b, by observing transits, where the brightness of a parent star dims from the planet crossing in front of it.
"This discovery confirms a new class of planetary systems that could harbor life," said Kepler Principal Investigator William Borucki of Ames Research Center. "Given that most stars in our galaxy are part of a binary system, this means the opportunities for life are much broader than if planets form only around single stars. This milestone discovery confirms a theory that scientists have had for decades but could not prove until now."
A research team used data from the Kepler space telescope, which measures dips in the brightness of more than 150,000 stars, to search for transiting planets. Kepler is the first NASA mission capable of finding Earth-size planets in or near the "habitable zone," the region in a planetary system where liquid water can exist on the surface of the orbiting planet.
Scientists said Kepler-16b is about the size of Saturn and thought to be made up of about half rock and half gas. The parent stars are smaller than the Earth’s sun. One is 69 percent the mass of the sun and the other is 20 percent.
Astronomers further observed that the brightness of the system dipped when the stars were not eclipsing one another, hinting at a third body, which is circling, not just one, but both stars, in a wide circumbinary orbit.
"Working in film, we often are tasked with creating something never before seen," said visual effects supervisor John Knoll of Industrial Light & Magic, a division of Lucasfilm Ltd. "However, more often than not, scientific discoveries prove to be more spectacular than anything we dare imagine. There is no doubt these discoveries influence and inspire storytellers. Their very existence serves as cause to dream bigger and open our minds to new possibilities beyond what we think we 'know.'"
This artist's concept illustrates Kepler-16b, the first planet known to orbit two stars -- what's called a circumbinary planet. The planet, which can be seen in the foreground, was discovered by NASA's Kepler mission.
Image credit: NASA/JPL-Caltech/T. Pyle
Kepler-16 orbits a slowly rotating K-dwarf that is, nevertheless, very active with numerous star spots. Its other parent star is a small red dwarf. The planetary orbital plane is aligned within half a degree of the stellar binary orbital plane. All these features combine to make Kepler-16 of major interest to studies of planet formation as well as astrophysics. Credit: NASA/JPL-Caltech/R. Hurt