Astronomers Discover Planetary System Orbiting Two Suns

Posted on August 29, 2012

Kepler 47 System

Astronomers using NASA's Kepler space telescope have discovered a planetary system orbiting two suns. The planetary system is located about 5000 light-years away from Earth, in the constellation of Cygnus (The Swan). The pair of stars whirls around each other every 7.5 days. One star is similar to our Sun while the other is a diminutive star only one third the size and 175 times fainter. This artist's concept illustrates Kepler-47, the first transiting circumbinary system. You can see a larger version of the image here.

Jerome Orosz (San Diego State University, USA), lead author of the study, says, "In contrast to a single planet orbiting a single star, planets whirling around a binary system transit a moving target. The time intervals between the transits and their duration can vary substantially, from days to hours, and therefore the extremely precise and almost continuous observations with Kepler space telescope were fundamental."

The inner planet, Kepler-47b, is only three times larger in diameter than the Earth and orbits the stellar pair every 49 days. The outer planet, Kepler-47c, is about 4.5 times the size of the Earth and orbits the stars every 303 days. This makes the outer planet the longest-period transiting planet currently known. The astronomers say the outermost planet is well within the habitable zone. The astronomers say it is probably a gas giant, but its moons could potentially harbour water and life.

William Welsh (San DiegoState University, USA), co-author of the study, says, "While the outer planet is probably a gas giant planet and thus not suitable for life, large moons, if present, would be interesting worlds to investigate as they could potentially harbour life."

Image: NASA/JPL-Caltech/T. Pyle