Finding life isn’t as simple as finding a planetary system like our own. Dwarf stars got some love recently with the discovery of the TRAPPIST system. Today, it’s binary stars’ turn in the spotlight. A planet with two stars is forever etched into our minds after watching Star Wars. Luke ponders his place in the galaxy as he stares at two setting suns.
Could science fiction turn into reality? Could life exist on a planet orbiting two suns? Scientists are out with new research, and the results are intriguing.
The Kepler-35 system was chosen for the hypothetical planet. It has two stars, Kepler-35A and B, and is already home to one planet. Kepler-35b is a gas giant about eight times larger than Earth. For this study, scientists nixed the gravitational influence of Kepler-35b and tossed in a water-covered, Earth-size planet.
Alright, let’s talk habitable zones. It works a little differently with two stars. Locating this sweet spot depends on the distance the planet is from the center of mass both stars are orbiting. There’s another wrinkle too. A planet around two stars wouldn’t orbit in a circle. It would wobble as it gets tugged on by both stars.
The hypothetical planet was placed in an orbital period between 341 and 380 days. Scientists then used models to see what kind of climate they were dealing with. At the outer edge of the habitable zone, the planet would see huge global average surface temperature swings of up to 3.6 degrees F over a year.
Siegfried Eggl, a Caltech postdoctoral scholar at NASA’s JPL, likens it to a desert on Earth where “we experience huge temperature variations from day to night.” Eggl says it’s all about the amount of water in the air. A colder atmosphere holds less moisture and less heat and leads to the drastic temperature swings.
But what about closer to the two stars? That’s where the climate gets a little more bearable. Global average surface temperatures would stay about the same all the time. More water vapor helps retain heat and keep temperatures much more comfortable.
If a planet drifts outside this sweet spot, life (as we know it) is a no-go. Too far out and get you a planet covered in ice. Think Hoth, but without these guys.
Too close and you get a planet choking on its own atmosphere. Venus is a perfect example.
As for the sunsets? The model shows mostly clear skies for double sunset viewing.
So, what does this study mean? I’ll let Max Popp, associate research scholar at Princeton and the Max Planck Institute of Meteorology, explain.
“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.”
The search for life continues. Studies like this only expand the potential list of places to look. Plus, it’s not just the habitable zone we need to look in. The habitable zone is defined as where a planet’s surface can support liquid water. But what about below the surface? NASA is revealing new discoveries of oceans beyond Earth later today on one of Saturn’s moons, possibly Europa or Enceladus.