16 Cygni B features a gas planet on a highly excentric orbit - Exoplaneten.de - The Exoplanet Directory

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16 Cygni B

April 15, 2016

The two double stars 16 Cygni A and B are about 53 light years away from Earth. Both stars circle the common center of mass once in 100,000 years at an average distance of 700 astronomical units . 16 Cygni B is very similar to the Sun. It is of almost the same spectral type (G3V), has the same mass and is about one third brighter.

Around this star, there is a very unusual planet [1]. 16 Cygni Bb is 1.67 times as massive as Jupiter. It shows one of the most eccentric orbits that have been detected so far for exoplanets. On its orbit, the planet approaches the star as close as 0.6 astronomical units, then moves back to 2.7 astronomical units away from it. If we put the orbit into our solar system for comparison, the planet would pass within the orbit of Venus at its closest point, while it would be far beyond the orbit of Mars at its farthest point. In the course of its orbit, the daytime temperatures range between + 120 ° C and -90 ° C at the upper edge of the atmosphere. These are very extreme temperature fluctuations.

One reason for this eccentric orbit might be the gravitational force of the other star, 16 Cygni A [2].

Similar to Jupiter, 16 Cygni Bb might have several moons. There composition may be comparable to the Jupiter moons, made up mainly of rock and ice. During an orbit of the planet around the star, the moons would also be exposed to the extreme temperature differences. The water of these moons might melt in the summer and freeze again in the winter. These moons would have a very young and highly dynamic surface.

Image above: View of the planet 16 Cygni Bb from one of its moons. The planet has reached its furthest point on the orbit. The icy temperatures have allowed the water of the moon to freeze. The planet exerts strong tidal forces on its moon, causing the surface of the moon to undergo constant changes.

This is just one of several possible representations that would be compatible with the planet's known data.


1. Cochran, W. D., Hatzes, A. P., Butler, R. P., & Marcy, G. W. (1997). The discovery of a planetary companion to 16 Cygni B. The Astrophysical Journal,483(1), 457.

2. Mazeh, T., Krymolowski, Y., & Rosenfeld, G. (1997). The high eccentricity of the planet orbiting 16 Cygni B. The Astrophysical Journal Letters, 477(2), L103.

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