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Planets Orbiting Double Stars Could Still Be Habitable, Study Finds

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One of the biggest questions since the National Aeronautics and Space Administration spotted a planet orbiting two stars in 2016 — reminiscent of Tatooine from Star Wars — was whether such a planet could support life and studies have been done to discover this.

Tech Times reported on March 1 that scientists found a rocky planet formation in the binary system SDSS 1557. Now researchers have taken it a step further by determining that a hypothetical Earth-like planet can support life and remain habitable for a long period of time — even when revolving around two suns.

A study to find out how well an Earth-like water planet would fare in a binary star system was published by Max Popp and Siegfried Eggl, postdoctoral fellows at the Jet Propulsion Laboratory of the California Institute of Technology. The two researchers used the binary star system Kepler 35-A and B as its model and studied the changing climate of Kepler 35b — an exoplanet roughly eight times the size of the Earth — if it was a water world.

Kepler 35b Conditions

Exoplanets orbiting binary stars are usually gas giants so what Popp and Eggl did was to work backwards with the hypothetical idea that 35b is a water world like Earth. In its current state, however, the exoplanet Kepler 35b is a giant planet that has 131.5 Earth days orbit around the Kepler AB system.

With the hypothetical assumptions in mind, Popp and Eggl expanded 35b's orbit range from 341 to 380 days, which would then move it around the Kepler 35AB's "habitable zone." From there, the two researchers studied 35b's resulting climate to determine if it will remain "habitable" or end up like the desert planet 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 says.

Uneven Conditions

Unlike our own solar system where planet climates practically remain constant, a planet orbiting a two-star system would experience greater climate variations because its own orbit is dependent on the gravitational interaction of the two stars. That is to say, the planet would not have a circular or elliptical orbit but a wobbly one.

Assuming that water world 35b has an Earth-like climate, Popp and Eggl ran the planet through a series of simulations to see how drastic the climate changes would be. The researchers found that drastic changes in climate were dependent on the presence of water vapor in the air.

Could Be Deadly When Pushed Back

When the simulation required 35b to be pushed back to the farther edge of the habitable zone, Popp and Eggl found that the global climate drastically changed, much like how the temperature on Earth's deserts change depending on the time of day. In fact, their computations show that the planet's climate could fluctuate by 3.6 degrees Fahrenheit (2 degrees Celsius) in a span of one year — a condition that could prove catastrophic for Earth at this time.

"The amount of water in the air makes a big difference," Eggl says.

If the planet is moved even a little farther — beyond the outer edge of the habitable zone — it will be completely covered in ice, much like a snowball.

Very Earth-Like When Moved Closer

In a situation where 35b is pulled closer to the two suns, just at the nearer edge of the habitable zone, Popp and Eggl found that the climates would have fewer variations and could even reflect Earth's own climate. This is because more water vapor would be present at the planet's surface, which would then act as a protection to keep the climate stable.

The main difference this will have with Earth is that 35b would have clearer skies due to less cloud formations, but it would not be a desert planet like Tatooine. The planet would actually be capable of keeping its water for a long period of time, and this environment would allow it to sustain life.

If, however, the planet is moved closer to the double suns, it would most definitely end up getting burnt from all the insulation and less likely to support life — much like our own solar system's planet Venus.

You can read the full research in the Nature Communications journal.

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