While astrobiologists continue to question the habitability of planets in systems of double stars, life may well arise on their natural satellites - the so-called ex-moons, if they orbit their planets within their zones of stability.
Indeed, life on planets, such as, for example, on the fantastic planet Tatooine from the movie "Star Wars", the sky of which is plowed by two suns at once, seems unlikely. The main reason for this seems to be that the interaction of gravitational forces in such systems poses a danger to the stability of the orbits of such planets. In a new study, Adrian Hamers and colleagues at the Institute for Advanced Research in Princeton have carried out computer simulations of the stability of 10 already known exoplanets in binary star systems.
As the researchers have already reported in the specialized monthly Monthly Notices of the Royal Astronomical Society, the models obtained demonstrate that near some of these planets there are still regions of stability, within which the potentially existing moons there may well become the cradles of life and places of its development. Outside of these zones of stability, such potentially existing moons are in danger of being thrown out of their systems, as a result of which the natural conditions on their surface would undergo catastrophic changes.
All the planets studied so far in this sense revolve around their stars at a very close distance, so they need no more than 7 days for one revolution. Both partner stars in such systems are also located quite close to each other, that is, they are only a tenth of the distance between the Sun and the Earth from each other (this distance is denoted as an astronomical unit = AE).
The created models show that near the modeled planets, stable moons would be quite possible if they orbit their planets at a distance of up to 0.01 AU, due to which the satellites would be less exposed to the gravity of the stars. In this regard, the mass of the mother planets should also play an important role: the greater the mass of the planet, the more stable its moon would look. The orbit of each particular moon also plays a vital role. “If the moon would revolve around the planet at an angle of about 90 degrees to the orbit of its planet, then the satellite's orbit would experience more and more“rolling roll”, which would eventually lead it to fall on the planet, and in some cases even to one of two stars,”the authors say.
By simulating the zone of stability around planets in binary star systems, it will be possible in the future to filter out and discard "false signals" that these planets have moons.