A team of astronomers from Israel, Europe, Korea and the United States has announced the discovery of a circumbinary gas giant in the habitable zone of its host pair of stars, a surprisingly common occurrence for circumbinary planets discovered by NASA’s Kepler/K2 mission.
Kepler-453b (right) orbits a pair of stars. Image credit: Mark Garlick, markgarlick.com.
Reminiscent of the fictional planet Tatooine in Star Wars, circumbinary planets orbit two stars and have two suns in their skies.
The newly-discovered circumbinary planet, named Kepler-453b, takes 240.5 days to orbit its parent stars, while the stars orbit each other every 27.3 days.
The larger star, Kepler-453A, is similar to our own Sun, containing 94% as much mass, while the smaller star, Kepler-453B, contains 20% as much mass and is far cooler and fainter.
The binary system lies in the constellation Lyra and is approximately 1,400 light-years from Earth. It is estimated to be between 1 and 2 billion years old, much younger than our Solar System.
Also known as KIC 9632895b, Kepler-453b has a radius 6.2 times greater than that of the Earth. Its mass was not measurable with the current data, but is likely to be less than 16 times that of the Earth.
According to the astronomers, Kepler-453b is the third Kepler circumbinary planet found to lie in the habitable zone of its host pair of stars.
Because of its size and gaseous nature, the planet is unlikely to harbor life as we know it. However, it may, like the gas giants in our Solar System, have large moons, and those moons could be habitable. Its orbit will remain stable for tens of millions of years, increasing the possibility of life forming on its moons.
With the number of known circumbinary planets now at ten, scientists can begin to compare different systems and look for trends. The systems tend to be very compact and they come in a wide range of configurations.
Once thought to be rare or even impossible, this and other Kepler discoveries confirm that such planets are common in our Milky Way Galaxy.
“The diversity and complexity of these circumbinary systems are wonderful. Each new circumbinary planet is a gem, revealing something unexpected and challenging,” said Prof William Welsh of San Diego State University, first author of a paper published in the Astrophysical Journal (arXiv.org preprint).
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William F. Welsh et al. 2015. Kepler 453b – The 10th Kepler Transiting Circumbinary Planet. ApJ 809, 26; doi: 10.1088/0004-637X/809/1/26
