Many Tatooine-like planets around binary stars may be habitable

Seattle – Luke Skywalker’s home planet star Wars It is the stuff of science fiction. But Tatooine-like planets orbiting pairs of stars may be our best bet in the search for habitable planets outside our solar system.

Many stars in the universe come in pairs. And many of these must haves planets that revolve around them (SN: 10/25/21). This means that there could be many more planets orbiting binaries than orbiting single stars like ours. But until now, no one had a clear idea of ​​whether those planets’ environments could be conducive to life. New computer simulations indicate that, in many cases, life can imitate art.

Earth-like planets orbiting some binary star formations can remain in stable orbits for at least a billion years, the researchers reported on January 11 at a meeting of the American Astronomical Society. The researchers suggest that this kind of stability would be enough to allow life to develop, provided the planets are not too hot or too cold.

Of the planets that stayed around, about 15 percent stayed in their habitable zone — the temperate zone around their stars where water can remain liquid — most or even all of the time.

The researchers ran simulations of 4,000 binary star configurations, each with an Earth-like planet in orbit around it. The team changed things like the relative masses of the stars, the sizes and shapes of the stars’ orbits around each other, and the size of the planet’s orbit around the binary pair.

The scientists then tracked the planets’ motion for up to a billion years from the simulation time to see if the planets would stay in orbit over the various time scales that would allow the emergence of life.

A planet orbiting binary stars can be expelled from the star system due to the complex interactions between the planet and the stars. In the new study, the researchers found that for planets with large orbits around pairs of stars, only about 1 out of 8 were ejected from the system. The rest were stable enough to continue in orbit for a full billion years. About 1 in 10 has settled in their habitable zone and has stayed there.

Of the 4,000 planets the team simulated, roughly 500 maintained stable orbits that kept them in their habitable zones at least 80% of the time.

“habitable zone.” . . “As I’ve described it so far, it goes from freeze to boil,” said Michael Pedowitz, the undergraduate student at the College of New Jersey at Ewing who presented the research. He said their definition is too strict because they chose to design Earth-like planets without atmospheres or oceans. This is simpler to simulate, but it also allows temperatures to fluctuate greatly on a planet as it rotates.

“The atmosphere and oceans will smooth out temperature changes fairly well,” says study co-author Maria McDonald, an astrobiologist also at the College of New Jersey. The abundance of air and water would likely allow the planet to maintain habitable conditions, even if it spent most of its time outside the nominal habitable zone around a binary star system.

The number of potentially habitable planets “will increase once we add atmospheres, but I can’t yet say how much,” McDonald says.

She and Pedowitz hope to build more complex models in the coming months, as well as extend their simulations beyond a billion years and include changes in stars that can affect conditions in the solar system as they age.

The possibility of stable, habitable planets in binary star systems is a matter of time, says Penn State astrophysicist Jason Wright, who was not involved in the study.

“in time star Wars He said, “We didn’t know of any planets outside the solar system, and we wouldn’t have done so for 15 years. Now we know that there are many more and that they orbit these binary stars.”

Wright says that these simulations of planets orbiting binaries could serve as guides for future experiments. “This is a group of planets that hasn’t been well explored. There’s no reason we can’t go after them, and studies like this should show us that it’s worth trying.”