Free Astronomy Magazine March-April 2022

36 MARCH-APRIL 2022 ASTRO PUBLISHING tem (also known as HIP 71865) has at least six times the mass of the Sun, making it by far the most massive system around which a planet has been confirmed. Until now, no plan- ets had been spotted around a star more than three times as massive as the Sun. Most massive stars are also very hot, and this system is no exception: its main star is a so-called B-type star that is over three times as hot as the Sun. Owing to its intense tempera- ture, it emits large amounts of ultra- violet and X-ray radiation. The large mass and the heat from this type of star have a strong im- pact on the surrounding gas, that should work against planet forma- tion. In particular, the hotter a star is, the more high-energy radiation it produces, which causes the sur- rounding material to evaporate faster. “B-type stars are generally considered as quite destructive and dangerous environments, so it was believed that it should be exceed- ingly difficult to form large plan- ets around them,” Janson says. But the new discovery shows planets can in fact form in such severe star systems. “The planet in b Centauri is an alien world in an environ- ment that is completely dif- ferent from what we expe- rience here on Earth and in our Solar System,” explains co- author Gayathri Viswanath, a PhD student at Stockholm Uni- versity. “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.” Indeed, the planet discovered, named b Centauri (AB)b or b Cen- tauri b, is also extreme. It is 10 times as massive as Jupiter, making it one of the most massive planets ever T he European Southern Obser- vatory’s Very Large Telescope (ESO’s VLT) has captured an image of a planet orbiting b Cen- tauri, a two-star system that can be seen with the naked eye. This is the hottest and most massive planet- hosting star system found to date, and the planet was spotted orbiting it at 100 times the distance Jupiter orbits the Sun. Some astronomers believed planets could not exist around stars this massive and this hot — until now. “Finding a planet around b Centauri was very exciting since it completely changes the picture about massive stars as planet hosts,” explains Mar- kus Janson, an astronomer at Stock- holm University, Sweden and first author of the new study published in Nature . Located approximately 325 light- years away in the constellation Cen- taurus, the b Centauri two-star sys- The VLT images planet around most massive star pair to date by ESO - Bárbara Ferreira