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Exoplanetary Scratchpad

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Systems containing planets orbiting more than one star.

Circumbinary Planetary Systems Web Pages[]

Circumbinary Planetary Systems In the News[]

Sample (Year)[]


  • Kepler-413 System - A red-dwarf orange dwarf binary system 2,300 ly way containing a circumbinary planet discovered by Kepler. The super-Neptune (65 ME) orbits the pair every 66 days. Its orbital precession causes it to vary its axis tilt by 30degrees every 11 years, which would cause wildly varying seasons. This type of precession observable at human timescales has never been observed before (Earth's is 23.5 degrees over 26,000 years). Also, its orbit is tilted 2.5degrees with respect to the plane of the star's orbital plane. This causes transits only to occur during a favorable line up period (three transits, followed by no transits, then five transits, the next predicted not until 2020), suggesting other planets that are not transiting now could transit in the near future.
  • Kepler-16 System - The first confirmed binary star found to have a planet revolving around both stars (a circumbinary planet, the previous one was uncertain and detected using astrometry), located 200 ly away. It is often compared to the Tattoine of Star Wars. It is a Saturn sized world thought to be of rocky and gaseous composition. It is at Venus-like distance from the center of gravity, but because the stars are so dim (70% SM and 20% SM), lies at the outermost portion of the habitable zone. A moon could potentially be habitable. The stars orbit each other every 41 days.
  • Kepler-47 System - The first multiplanet circumbinary star system found. Contains a yellow and red dwarf. The inner planet has 3 times Earth's radius and a period of 49 days. This planet is thought to have a thick blanket of methane haze around it. It is the smallest known transiting circumbinary planet. The outer planet is the furthest known transiting exoplanet with a period of 303 days. It is a Uranus-sized planet in the habitable zone. The stars go around each other once every week, causing the planet to experience several percentages of difference in temperature. Assuming a 24 hour day, they would rise and set about 30 minutes after each other, and can also be seen regularly eclipsing each other. A moon around this planet could be habitable. This system challenges planetary system formation theories. Planet c, unlike other known circumbinary planets, orbits far enough out to not need to have formed out further than it is today.


  • HR 7162 System - Binary star system (aka HD 176051) with a period of about 61 years consisting of a 1.07 and 0.7 mass stars. Astrometry has discovered a planet (nicknamed Inrakluk by its discoverers) around one of these stars (one of many such claims to be first planet discovered with this technique), though it is not certain which star it is orbiting. If it is orbiting the smaller star, it is 1.5 MJ and 1.76 AU, while if it is orbiting the larger one, it is 2.26 MJ and 2.02 AU. Its existence presents a challenge to the core accretion model because the other star is close enough that it should have disrupted any such material before a planet could have formed. This supports the gravitational collapse method, which could have occurred much quicker. The planet is often compared to Tattoine.

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