SEATTLE — Star Wars' home planet is fiction. However, Tatooine-like planets in orbit around two stars may be our best bet in the search for habitable planets beyond our solar system.
Many stars in the universe are made up of pairs. Many of them should have planets orbiting them (SN: 10/25/21). But until now, no one had any clue whether or not life could exist within them. New computer simulations suggest that life may in many cases imitate art.
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Researchers said that earthlike planets orbiting some binary stars might last for at least a billion years. This sort of stability, they believe, would be sufficient to allow life to flourish, provided the planets aren't too hot or cold.
About 15% of the planets that stayed around stayed in their habitable zone, or temperate area around their stars, most or even all of the time.
The researchers used simulations of 4,000 binary stars, each with an Earthlike planet in orbit around them. The results varied from what they found, to the sizes and shapes of the stars' orbits around each other.
After a billion years of simulated time, scientists examined the planets' movements to see if life would be allowed to develop.
Because of complicated interactions between the planet and the stars, a planet orbiting binary stars may be kicked out of the star system. Only about one out of every eight planets was kicked out of the system, while the other was stable enough to continue to orbit for a billion years.
Around 500 of the 4,000 planets that were simulated by the team maintained stable orbits that kept them in their habitable zones for at least 80 percent of the time.
"The habitable zone," according to Michael Pedowitz, an undergraduate student at the College of New Jersey in Ewing who presented the study, ranges from freezing to boiling. That's because they chose to model Earthlike planets with no atmospheres or oceans. That's also easier to simulate, as the planet orbits.
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According to study coauthor Mariah MacDonald, an astrobiologist at the College of New Jersey, an abundance of air and water might allow a planet to maintain habitable conditions, even if it spent more time outside the nominal habitable zone.
MacDonald predicts that the number of potentially habitable planets will increase when we add atmospheres, but I can't yet say by how much.
In the next months, Pedowitz and she intend to expand their simulations beyond a billion years and include observations that may alter conditions in a solar system as it age.
According to Penn State astrophysicist Jason Wright, the possibility of stable and habitable planets in binary star systems is a timely concern.
"We didn't know there were any planets outside the solar system at the time Star Wars was published," says the author, "now we know that there are many more than these binary stars."
Wright believes that future simulations of planets orbiting binaries will be useful. "There is no reason we should not pursue this species of planets," says the author.