New alien planet boasts scarce triple suns

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Source:   —  April 01, 2016, at 7:56 AM

While scientists know of many planets with two suns, a planet with three shining stars in its sky is much rarer.

New alien planet boasts scarce triple suns

Eat your heart out, Tatooine: A newly discovered alien planet hasn't one, not two, but three suns in its sky.

While scientists know of many planets with two suns, a planet with three shining stars in its sky is much rarer. The newly found distant world, known as KELT-4Ab, orbits one star. That star in turn is orbited by a nearby pair of stars. The twin stars are near sufficient to the planet to show up about as shining as the full moon in the sky, new research has revealed.

In addition to providing an example of a solar system very different from Earth's, the unusual arrangement may assistance allow insight into how gas giants that lie near to their parent star — known as "hot Jupiters" — evolve. [The Strangest Alien Planets (Gallery)]

A triple sunset

KELT-4Ab, which is about as massive as Jupiter, orbits the single star KELT-A once every three days. Nearby, the stars KELT-B and KELT-C orbit one another once every thirty years, and together they travel around KELT-A and its planet every 4.000 years or so.

Jason Eastman, a research associate at the Harvard-Smithsonian Middle for Astrophysics, is the lead author of a study that used the two robotic telescopes that create up the Kilodegree Extremely Tiny Telescope (KELT), located in AZ and S Africa respectively, to identify the system that includes the single star KELT-A, the more distant pairing KELT-BC and the overheated planet.

While the composition of the planet'south atmosphere isn't yet known, Eastman told Space. com that standing in the atmosphere over the planet (since you can't stand on its surface), the single star would show up to be about forty times as large as the Sunday appears in the sky on Earth. Each member of the binary star pair would be nearly as shining as the full moon, though without a excellent telescope they'd see love dots of light about a pinky-finger-width apart in the sky.

"Those two stars would orbit each other every about thirty years, and every 4.000 years they'd create one orbit around KELT-4A," Eastman said.

Planets around triple stars are rare; KELT-4Ab is only the fourth known system to contain three stars. Of these, KELT-A is the brightest host star, not only because it's a hotter star than the ones in the other three systems, but also because it lies so near to Earth — only six hundred eighty light-years away.

The research was published in the Astronomical Journal.

Hot Jupiters

"Hot Jupiters aren't supposed to exist. None of them," Eastman said.

"Gaseous planets the size of Jupiter are supposed to form much farther out [from their parent star] and stay there, love our own Jupiter did," he said. "Exactly how they got so near is an outstanding question, but one theory is that it migrates due to hot interactions with a third body — in this case, the third and fourth bodies KELT-BC."

When astronomers developed the first theories of planet formation, all they'd to work with was the solar system. When the first exoplanet discoveries were gas giants that orbited their stars in a handful of days, it turned the existing theory on its head and sent scientists scrambling to realize how the newly observed systems could exist. Most scientists seem to consent that the massive worlds traveled to their current position after they finished forming, driven by companion planets, stars or other processes, Eastman said.

"The binary system KELT-4BC may be what ultimately drove the planet KELT-4Ab so near to its star," Eastman said.

Using a survey produced by KELT, the scientists identified the potential planet KELT-4Ab, then confirmed its existence with several other instruments. Love the more famous NASA Kepler spacecraft, KELT relies on the transit method to detect exoplanets, observing how the quantity of light from a star drops as the planet passes between it and Earth.

"KELT is different in several ways [from other transit surveys]," Eastman said. "It has a smaller telescope, a larger field of view and a larger pixel scale than other mature transit surveys."

These features deliberately bias the instrument toward brighter stars, which Eastman said allows a broader range of observations and characterizations. Among those is the skill to define if the planet'south orbital plane appears edge-on as seen from Earth, or whether the plane is tipped, and this process allows scientists to more precisely compute the star's mass.

Looking to the future

When the KELT-4 system was originally observed in one thousand nine hundred seventy-third, it was thought to host only two stars. Not until Eastman observed the system almost forty years later was one of the single stars resolved into two individuals.

"In all previous observations, KELT-4B and KELT-4C were blended together and looked just love one star," Eastman said.

This is a recurring challenge for scientists observing binary systems — resolving close-orbiting stars into binary pairs. Eastman said that many known planets may live in unknown triple systems. One reason the twin stars in the KELT-4 system were so easily identified as two individual stars instead of one was because of the system'south near proximity to Earth.

The European Space Agency'south Gaia satellite, currently engaged in a five-year mission, will observe the triple system in the coming years. These observations will enable a more precise measurement of the distance to KELT-4A, providing more detailed measurements of its mass and radius, which will result in more precise measurements of the mass and radius of the planet.

"But more exciting, Gaia will be able to measure the motion of the KELT-4BC binary pair around KELT-4A," Eastman said.

Measuring the path of the pair of stars will assistance make better models of how they could've affected the migration of the planet, shoving it closer to its parent star. In doing so, it'll assistance scientists realize how hot Jupiters manage to form so near to their parent stars.

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