Gas giant 11 times the mass of Jupiter discovered in b Centauri binary system

Orbit roughly 100 times wider than that of similar planets in our solar system

Scientists have discovered a gas giant planet 11 times the mass Jupiter orbiting the binary system of b Centauri A and B.

The b Centauri star system, located roughly 325 light years from our solar system, hosts stars with a combined mass between six and 10 times that of the Sun.

A team led by Markus Janson, an astronomy professor at Stockholm University, has confirmed the existence of the distant gas giant, about 11 times the mass of Jupiter, using data from the European Southern Observatory's Very Large Telescope in Paranal, Chile.

The results – written up in Nature this week – show that planets can reside in much larger stellar systems than previous research has suggested, improving our understanding of the planet formation process. Previous research had suggested it would be rare to find gas giants orbiting stars with more than 3 solar masses.

Janson and colleagues made observations between March 2019 and April 2021 and found the celestial body orbiting its binary stars at 560 times the distance between Earth and the Sun, 100 times wider than Jupiter's current orbit.

The findings led the researchers to conclude the planet they dubbed b Cen (AB)b probably formed rapidly close to its present location from a dense clump of matter that accumulated within a disk that used to orbit b Cen AB.

Kaitlin Kratter, associate professor of astronomy at the University of Arizona, commented that the study of exoplanets had come a long way since tiny rocky worlds were revealed to be in orbit around massive neutron stars in 1992 – the first planet-like objects to be detected outside our solar system.

Unlike the early exoplanets, which were discovered through the wobbling of their host stars, b Cen (AB)b was found through direct observation. Kratter said separating the light of the planet from the background was equivalent to capturing a single Christmas light in a football stadium illuminated by 500 floodlights.

Janson's study provides evidence suggesting how such massive binary star systems might form, which has so far been a subject of debate among astronomers.

The work shows that a binary system can host a long-lived massive disk of gas and dust. "It therefore suggests that this massive binary formed in a similar way to stars with lower mass – by accreting gas from a disk," Kratter said. ®

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