Circumbinary planet

A zirkumbinärer planet is a planet that revolves around a double star.

Formation

It is believed that the double stars and they are originated from a common accretion disk orbiting planets. One indication of this is that all orbits of circumbinary planets that have been certified by the transit method, are coplanar, ie the orbit of the binary system and that of the planet in one plane. Another indication is the measurement of the Rossiter - McLaughlin effect, after which the rotation axis of the circumbinary planet is perpendicular to its orbital plane and rotate the planet in the direction of their orbit. However, they can not be incurred at the place at which they are observed. Within ten astronomical units the dynamic effects on the orbits of the planetesimals are so large that they revolve in elliptical orbits around the binary star system. In a collision, these planetesimals destroy rather than to stick together and form a planet due to the large relative velocities. The circumbinary planets are therefore subsequently migrated to their current location as the hot Jupiter.

Determination of the mass

The radii of the planets can be determined by the depth of the light decrease in transit, but not their masses. However, influence circumbinary planet - unlike planets around single stars - and the path of the central binary system. From the displacements caused by the planet occultations and from the small time variations in the pre- courses through the disk of the two stars is the masses of the planets can be estimated when the masses of binary stars are known. As for stability reasons but orbit the planets in wide orbits around the common gravitational center are currently no exact values ​​.

Evidence

Transit method

Are indisputable evidence of circumbinary planets by the transit method, so if they are in the pre-transition before the stars of the binary system cause a little darkening of the star's surface ..

Light travel time effect

Due to the light-time effect in eclipsing stars circumbinary planets can be only suspected before. An indirect detection of circumstellar planets can be done by the changes in the times of minimum brightness by a light covering alternation of the two stars in a binary star system.

This deemed by the light-time effect planets have been displayed in HW Vir, Vir NY, UZ For, RR Cae, HU Aqr, DP Leo, NN Ser and NSVS 14,256,825. None of these planetary orbits seem to be coplanar, as it has not been able to observe transits through the planets in these binary systems. Furthermore, many of the paths are not dynamically stable over a longer period, as the planet masses adopted would be very high in order to have a measurable impact on the stars. Furthermore, it is so far not been able to predict the future course of the deviations from a linear ephemeris Bedeckungsminima as overlapping effects such as mass transfer affect the timing minimum brightness on the stars between the stars or magnetic activity. The suspected about the light travel time effects circumbinary planets still require independent confirmation.

Examples

Until October 15, 2012 circumbinary planet have become known by the transit method in the following binary systems:

  • PSR B1620 -26
  • Kepler - 16b
  • Kepler -34
  • Kepler -35
  • Kepler -38
  • Kepler -47
  • Ross 458
  • PH1.
Accretion disc Rossiter–McLaughlin effect PSR B1620-26 b Kepler-47 PH1b arXiv Digital Object Identifier
837289
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