A habitable planet orbiting in a binary star system like the desert planet Tatooine in the science fiction adventure film Star Wars could actually exist, a new study reveals. In fact, an Earth-sized planet with two parent stars could very well be habitable if it orbits at just the right distance from each of the stars. And it is quite possible that instead of being a hot planet of sand and desert and scorched surfaces, the planet could be a waterworld.
Using a model of the binary star system Kepler 35A and B (which actually has a planet in orbit, albeit a gas giant that was ignored for the purposes of the study), scientists were able to determine that rocky, Earth-type worlds could exist under two suns without necessarily having the characteristics of a desert world like Tatooine's depiction in Star Wars. Phys.org reports that the study presents the case for planets that might not even have deserts at all and suggests that watery worlds were also possible, maintaining orbits at a "particular range of distances from two sun-like host stars" where "a planet covered in water would remain habitable and retain its water for a long time."
Which is just the opposite of the famous Tatooine.
"This means that double-star systems of the type studied here are excellent candidates to host habitable planets, despite the large variations in the amount of starlight hypothetical planets in such a system would receive," Max Popp, associate research scholar at Princeton University in New Jersey, and the Max Planck Institute of Meteorology in Hamburg, Germany, said of the study's findings.
For the study, Popp and study researchers added a hypothetical water-covered, Earth-size planet around the Kepler 35 AB stars. They then observed how this planet's climate would evolve as it orbited the host stars, giving it orbital periods between 341 and 380 days.
The research found that the habitable zone for a binary star-orbiting planet would depend on the distance from the center of mass of the two stars. Such a planet also would not travel in a circular orbit. It would wobble through the gravitational interaction with the two stars.
A waterworld located on the outer edges of its particular habitable zone would be rather cold and have a varying surface temperature of 3.6 degrees Fahrenheit (2 degrees Celsius) over a year's time. This would be due to the small amount of water vapor in the atmosphere and would be analogous to conditions on Earth in desert regions.
The same planet orbiting on the inner edge of the habitable zone would find its temperatures fairly consistent over time, its surface temperature nearly constant. More water vapor would present a buffer to ensure more comfortable weather conditions.
The model also revealed that a waterworld circling two suns would have less cloud coverage, giving clearer skies for the double sunsets. This was a particularly effective and memorable scene in Star Wars, when the young Luke Skywalker witnessed the setting of the two suns of Tatooine.
"Our research is motivated by the fact that searching for potentially habitable planets requires a lot of effort, so it is good to know in advance where to look," Eggl said. "We show that it's worth targeting double-star systems."
Since red dwarfs are the most common stars in the universe, it is apparent that there will be many more red dwarf pairings than any other tandem lineups of star types. Given this, it is also known that red dwarfs are particularly volatile at young ages, expelling bursts of atmosphere-stripping radiation. This could be problematic for the potential habitability of many Tatooine-like planets.
The first Tatooine-like planet discovered was announced in September, 2011, according to Space. NASA, using the Kepler Space Telescope, detected a Saturn-sized exoplanet orbiting the star Kepler 16 about 200 light years away. The large planet was nicknamed, as would be expected, Tatooine.
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