Don’t forget the sunscreen on planet HD 131399Ab: It has three suns.
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This composite image shows the newly discovered exoplanet HD 131399Ab in the triple-star system HD 131399.
Astronomers on the hunt for planets with real star quality have found themselves a triple threat: On Thursday, a paper in Science announced the discovery of planet with three suns. The planet appears vastly brighter in this image than it would in reality, compared to the stars.
It sounds like science fiction, but it’s all gravity. What’s more, a year there lasts half a millennium from Earth’s perspective. Scientists suspect it may have started off in a much closer orbit around two parent stars before it was gravitationally bounced to its extreme distance. Wagner and his team have several theories about how HD 131399Ab could have formed around one of the stars, where it was then ejected into its current orbit.
The astronomy team spotted the planet using the SPHERE instrument on the European Southern Observatory’s (ESO) Very Large Telescope in Chile. The SPHERE imager on the ESO Very Large Telescope in Chile took the images.
This artist’s impression shows a view of the triple star system HD 131399 from close to the giant planet orbiting in the system.
In this case, direct imaging doesn’t mean scientists snapped a high-res photo but, rather, that they were able to collect data straight from the world itself instead of relying on the analysis of changes in starlight, as is the case for most exoplanet detections. We can tell us quite a bit about what a planet is like by studying its infrared signal.
Its mass is believed to be four times that of the gas giant Jupiter, which is our solar system’s largest planet. “Piecing together how planets form in general can help us to understand how our own solar system formed and became habitable, and can inform us about where else habitable planets could exist in our own galaxy”, says Dr Wagner.
“It is not clear how this planet ended up on its wide orbit in this extreme system. but it shows there is more variety out there than many would have deemed possible”, Wagner said.
The most massive star of this triplet, HD131399A, which is about 80 per cent more massive than the sun, is orbited by the other two, less massive, stars B and C at a distance of 300 astronomical units (1 au is equal to the average distance of the earth from the sun.) While orbiting star A, stars B and C also move around each other, like a twirling dumb bell, at a distance of approximately 10 au. This makes the discovery extra surprising.
Astronomers have detected the first ever exoplanet to traverse a wide orbit in a chaotic triple star system.
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However it came to be, that far-flung orbit makes the world a flawless candidate for direct imaging methods such as SPHERE: More traditional exoplanet-hunting tools such as Kepler get information about a planet only when it passes in front of its host star from Earth’s perspective (which we call a transit). “Certainly having this rich example could teach us a lot”. And you have! This isn’t the first triple-star system found to contain exoplanets. The planet is now known as 131399Ab and appears in the lower-left corner of the picture.
