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Astronomers discover enormous planet in extreme, massive star system

Astronomers have discovered a planet some previously thought to be impossible, orbiting an enormous and extremely hot star system. The planet, which orbits the two-star system b Centauri, is challenging assumptions about where planets can form.

Artist’s impression showing a close up of the planet b Centauri b.
This artist’s impression shows a close-up of the planet b Centauri b, which orbits a binary system with mass at least six times that of the Sun. This is the most massive and hottest planet-hosting star system found to date. The planet is ten times as massive as Jupiter and orbits the two-star system at 100 times the distance Jupiter orbits the Sun. ESO/L. Calçada

Located in the constellation of Centaurus, 325 light-years away, the b Centauri system consists of two stars with a combined mass at least six times that of our sun. Massive stars tend to also be very hot, as this system is, with its main star being three times hotter than the sun.

This combination of massive and very hot stars does not lend itself to planet formation, and until now no planets had been discovered orbiting a star more than three times the mass of the sun. But in the case of b Centauri, there is a planet orbiting at around 100 times the distance of Jupiter from the sun which was detected using the European Southern Observatory’s Very Large Telescope.

“Finding a planet around b Centauri was very exciting since it completely changes the picture about massive stars as planet hosts,” said Markus Janson, an astronomer at Stockholm University, Sweden, in a statement. “B-type stars are generally considered as quite destructive and dangerous environments, so it was believed that it should be exceedingly difficult to form large planets around them.”

As befits a body orbiting a massive star, the planet itself is massive too. It is estimated to be 10 times the mass of Jupiter, which makes it one of the most massive exoplanets detected to date. Astronomers speculate that the planet was able to survive the high temperatures and harsh radiation given off by the stars because it orbits so far away from them.

The whole system is an intriguing contrast to our solar system and most known exoplanets. “The planet in b Centauri is an alien world in an environment that is completely different from what we experience here on Earth and in our Solar System,” said co-author Gayathri Viswanath, a Ph.D. student at Stockholm University.

“It’s a harsh environment, dominated by extreme radiation, where everything is on a gigantic scale: The stars are bigger, the planet is bigger, the distances are bigger.”

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