Milky Way: millions of planets with two suns?

Discovery of new binary star planets indicates high frequency

This is how the newly discovered planet Kepler-35b could look © Lynette Cook
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There are probably millions of planets in the Milky Way that have two suns. This conclusion draws astronomers, after they have again discovered two such planets in different binary systems. Thus, the number of known celestial bodies of this kind has risen from zero to three within a few months. Only in September 2011 had astronomers discovered a planet in a binary system for the first time. This type of planet is no longer an absolute exception, but rather forms its own, quite common planetary class, the astronomers report in the journal "Nature".

"It used to be thought that the environment around such a pair of stars would be too chaotic to allow the formation of a planet, " says lead author William Welsh of San Diego State University. The new findings showed that it is not only possible but also probable that there are millions more of such planets in our galaxy.

The scientists detected the planets with the space telescope Kepler. The sensitive optics of the telescope registers the tiniest variations in brightness in the light of stars. These arise, among other things, when a planet passes in front of its star and so its light briefly dimmed a bit.

Saturn-sized gas planet orbits two sun-like stars © Mark A. Garlick

750 double stars examined in detail

For their study, the astronomers had studied the brightness data of 750 double stars closer. The finding of several planets in such a small sample indicates that more than one percent of all binary stars in the vicinity could have large gas planets, the researchers say.

"The hunt for more binary star planets is thus opened, " comments co-author Joshua Carter of the Harvard Smithsonian Center for Astrophysics in Cambridge, USA. In the next few years, they want to use the space telescope Kepler purposefully. display

Gas planets of the size of Saturn

The two new planets Kepler-34b and Kepler-35b are 4, 900 and 5, 400 light-years from Earth in the constellation of swan. Both are gas planets and about as big as Saturn in our solar system.

Kepler-34b orbits its two sun-like stars once in 289 days. His orbit is only a little farther than the orbit of the earth around the sun. Kepler-35b needs 131 days for an orbit, its orbit is slightly narrower than that of Venus.

Kepler-35b owns two suns Lior Taylor

Just outside the living-friendly zone

As the researchers report, both planets are located just outside of the living-friendly zone. This zone is the area of ​​a planetary system where temperatures are mild enough to allow for liquid water and life on a planet. Kepler-34b is a bit too cold for that, but Kepler-35b is a bit too hot, the researchers say.

In all three known binary star planets, the orbits of the stars and their planets lie on one level. This suggests that the planets were once formed together with their stars from a disk of material, explain Welsh and his colleagues. (Nature, 2012; doi: 10.1038 / nature10768)

(Nature / dapd, 13.01.2012 - NPO)