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Janson is the first author of the new study, published Dec. “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 in Sweden, in a statement. And the problem with forming planets around such hot stars is that they emit lots of powerful ultraviolet and X-ray radiation, which ought to disrupt the planet-forming process. The system’s larger star is of spectral type B, the second-hottest category. That might not seem like much, but it’s at least twice the mass of any other known star (or stars) confirmed to host a planet. Objects with masses of 13 Jupiters or more are classified as brown dwarfs, or failed stars.īut it’s the two host stars that make this system truly unlike any other astronomers have yet seen: The stars have an estimated combined mass of six to 10 times that of the Sun. The planet’s mass is roughly 11 times that of Jupiter, which places it in the upper range of objects that can still called planets. (The apparent rings around the star and planet are image artifacts, and the object in the upper right is an unrelated background star.) This makes it one of the most distant exoplanet orbits yet found. It’s a gas giant orbiting its host stars at a distance roughly 560 times that of Earth from the Sun. By convention, the first discovered planet in a system is given the suffix “b”, which results in the unusual name: b Centauri b. The arrow in the image above points to the planet. At magnitude 4, b Centauri, located some 325 light-years away, is visible to the naked eye - though it is not to be confused with Beta (β) Centauri, which is one of the brightest stars in the sky.
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The image, taken by the Very Large Telescope at the European Southern Observatory in Chile, shows the binary star system b Centauri at left, its two stars not quite resolved. The planet b Centauri b arguably shouldn’t even exist - but the picture above is confirmation that it does.
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