16-million-year-old planet with three suns discovered



Don't forget the sunscreen on planet HD 131399Ab: It has three suns.

The far-off planet, located about 320 light years from Earth in the constellation Centaurus, is unlike any other known world, scientists say.

Anyone on the planet — if it harbored life, which scientists don't think is possible — would either experience constant daylight or enjoy triple sunrises and sunsets each day, depending on the season, which last longer than human lifetimes.

The orbit of the 16-million-year-old planet is by far the widest known path within a multi-star system. And, surprisingly, it's quite stable, scientists announced in a study published Thursday in the journal Science.

Typically, the complex gravitational attractions from other suns in such a system render the orbit unstable, meaning the planet could be ejected from its path.

"We were surprised to find the planet in an orbit so long that it could be influenced by all three stars," said astronomer Daniel Apai of the University of Arizona and one of the study co-authors.

The planet takes around 600 years to orbit its main sun. Since the planet was discovered about a year ago, astronomers have only seen a tiny fraction of its elliptical orbit. Apai said scientists' best guess is that the planet mainly orbits the most massive and brightest star in the system, labeled star A.

"In the few other systems where planets and multiple stars co-exist, the planets have usually been seen very close to one star and very far from the other, therefore the planet’s orbit was always dominated by one star," Apai said.


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If researchers are wrong and its orbit is longer, "it could swing to the other stars and back, an orbit which in most cases would lead to the planet being slingshotted out of the system," Apai said.

The planet was discovered by astronomers using the European Southern Observatory's "Very Large Telescope" in Chile. It is one of the youngest exoplanets — planets outside our solar system — discovered to date.

Kevin Wagner, the study lead author and discoverer of the planet, said this is the only planet they've discovered so far in this system, but there could also be other planets orbiting the other two stars.

It's unlikely there's life on the planet, which is gaseous, just like Jupiter in our solar system, Apai said.

"It has quite high temperatures, no liquid water, extremely powerful winds, and no surface; just below the uppermost layer of the atmosphere it rains liquid iron droplets," he said. "Earth-like life — life as we know it — would be extremely unlikely, if not impossible, to exist in this atmosphere."

Wagner said it's possible that if the planet has moons, they could harbor some form of life, just as Jupiter's moons might in our solar system.

Source: usatoday

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