This is a comparison of the relative sizes of several Kepler circumbinary planets. Kepler-1647 b is substantially larger than any of the previously known circumbinary planets. Credit: Lynette Cook
If you cast your eyes toward the constellation Cygnus, you’ll be looking in the direction of the largest planet yet discovered around a double-star system. It’s too faint to see with the naked eye, but a team from Goddard Space Flight Center and San Diego State University, used Kepler Space Telescope to identify the new planet, Kepler-1647b, 3,700 light-years away and ~4.4 billion years old, roughly the same age as Earth. The stars are similar to the sun, with one slightly larger than our home star and the other slightly smaller. The planet has a mass and radius nearly identical to that of Jupiter, making it the largest transiting circumbinary planet ever found.
Planets that orbit 2 stars are known as circumbinary planets, or sometimes “Tatooine” planets.” Using Kepler data, astronomers search for slight dips in brightness that hint a planet might be passing or transiting in front of a star, blocking a tiny amount of the star’s light. “But finding circumbinary planets is much harder than finding planets around single stars,” said SDSU astronomer William Welsh. “The transits are not regularly spaced in time and they can vary in duration and even depth.”
The planet takes 1,107 days – just over 3 years – to orbit its host stars, the longest period of any confirmed transiting exoplanet found so far. The planet is also much further away from its stars than any other circumbinary planet, breaking with the tendency for circumbinary planets to have close-in orbits. Interestingly, its orbit puts the planet with in the so-called habitable zone.
Like Jupiter, however, Kepler-1647b is a gas giant, making the planet unlikely to host life. Yet if the planet has large moons, they could potentially be suitable for life. “Habitability aside, Kepler-1647b is important because it is the tip of the iceberg of a theoretically predicted population of large, long-period circumbinary planets,” said Welsh. Once a candidate planet is found, researchers employ advanced computer programs to determine if it really is a planet. It can be a grueling process.
Laurance Doyle, a coauthor on the paper and astronomer at the SETI Institute, noticed a transit back in 2011. But more data and several years of analysis were needed to confirm the transit was indeed caused by a circumbinary planet. A network of amateur astronomers in the Kilodegree Extremely Little Telescope “Follow-Up Network” provided additional observations that helped the researchers estimate the planet’s mass. http://www.nasa.gov/feature/goddard/2016/new-planet-is-largest-discovered-that-orbits-two-suns
Recent Comments