Saturday, February 13, 2021

What are the Circumbinary planets?

All Star Wars lovers will have dreamed at least once of being on Tatooine to witness the suggestive sunset of the two suns that is shown several times throughout the films.

Planets orbiting two stars like Tatooine (which are called circumbinary planets) until a few years ago were only the result of science fiction. Today, however, several of these planets are known, the first confirmed of which was Kepler-16b, discovered in 2011.

In fact, Kepler-16b orbits around two stars both smaller than the Sun, an orange dwarf with a diameter two thirds the solar one and a red dwarf with a diameter one fifth of that of our star. The system is located 200 light years away from the Solar System.

However, the similarities between Kepler-16b and Tatooine are only related to their orbital parameters. In fact, Tatooine is obviously a habitable world, while Kepler-16b is a gas giant with dimensions similar to that of Saturn.

The exoplanet is located at the outer limit of the habitable zone, that is, the region in which liquid water on the surface can exist. Being a gas giant, Kepler-16b does not have a solid surface, but in orbit around it there may be some satellites large enough to hold an atmosphere capable of keeping liquid water on the surface. On these hypothetical satellites (even if this is very unlikely) the conditions suitable for the development of elementary life forms could therefore exist.

Credit: NASA / JPL-Caltech / T. Pyle.

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