Search This Blog

Saturday, July 9, 2016

A newfound alien planet is bullied by three suns

A newly discovered alien world has three masters.

The planet — which is about four times more massive than Jupiter and located about 340 light-years from Earth — orbits the brightest star in a three-star system.
The two other stars in the system also orbit the brightest star, circling one another like a dumbbell and exerting their gravitational influence over the planet, named HD 131399Ab.
"For about half of the planet's orbit, which lasts 550 Earth-years, three stars are visible in the sky," Kevin Wagner, the lead author of a study in the journal Science detailing the new finding, said in a statement. He added:
For much of the planet’s year the stars appear close together, giving it a familiar night-side and day-side with a unique triple-sunset and sunrise each day. As the planet orbits and the stars grow farther apart each day, they reach a point where the setting of one coincides with the rising of the other — at which point the planet is in near-constant daytime for about one-quarter of its orbit, or roughly 140 Earth-years.
Is it stable?
According to the study, HD 131399Ab's orbit brings it billions of miles away from its host star. The equivalent in our solar system would be a planet twice as far as Pluto from our sun.
HD 131399Ab also seems to have a tenuous hold on its orbit.
"If the planet was further away from the most massive star in the system, it would be kicked out of the system," Daniel Apai, a co-author of the study said in a statement.
Apai added that computer simulations show that this world could have been kicked out of its orbit if the star system changed just slightly.
Even still, it isn't a sure thing that the world will be in a stable orbit forever.
"It is not clear that the planet's orbit is stable over long periods of time, so it might be that we are catching this system in a special state in which the planet hasn't yet been ejected from the system,"
The planet and its stars are also unique in its own right,
"This system is surprising in that it is a planet found in a stellar system containing three stars, and in which all three stars exert a strong gravitational influence on the planet."
How to photograph a planet
HD 131399Ab was discovered with the Very Large Telescope in Chile by taking photos of the star system in infrared light.
Most methods for finding exoplanets — planets outside of our solar system — are more indirect, either hinging upon detecting minute dips in a star's light as a planet moves across its face, or watching for a "wobble" in a star produced by the gravitational tug of a large planet.
But this world was found using a "direct imaging" technique, which lets scientists literally "take a picture of a planetary system and study the light emerging from an exoplanet independent of its host star," Johnson said.
"High-contrast imaging surveys like this one are the only means of discovering planets in wide orbits around their stars, where wide is further away from the central star than Saturn is from the sun," Johnson added.
This world isn't the only planet found in multi-star systems.
Scientists have also found exoplanets in star systems boast two stars — colloquially known as "Tatooine" planets after Luke Skywalker's home world in Star Wars — and other planets have been found in three-star systems.
Researchers are particularly interested in learning more about these kinds of planetary systems to figure out exactly how uncommon they are.
"I think the next step is a dedicated imaging survey around multi-star systems to see if this type of system is a class of astronomical objects, or an aberration," Johnson said.…/…/2016/07/06/science.aaf9671…/20…/newly-discovered-planet-has-3-suns…/alien-planet-found-in-three-star-sy…/……/2016-07/uoa-ndp070116.php…

Cecile G. Tamura