SPHERE directly images a large orbiting gas giant in a nearby binary system


Named b Centauri (AB) b (or b Centauri b), the new exoplanet is estimated to be only 15 million years old and 10 times the mass of Jupiter, according to an analysis of data collected by the high-contrast spectro-polarimetric exoplanet . Finding aid (SPHERE) mounted on ESO’s Very Large Telescope (VLT).

Artist’s impression of b Centauri b and its star guests. Image credit: ESO / L. Calçada.

The Centauri b system is located approximately 318 light years away in the constellation Centaur.

Also known as b Cen (but not β Cen), HR 5471 or HIP 71865, it consists of a pair of nearby stars.

The most massive star is named b Cen A and has a type B2.5, corresponding to an effective temperature of around 18,000 K. The properties of the second star, b Cen B, are uncertain.

The system is around 15 million years old and probably belongs to the Upper Centaurus Lupus star association.

“Most massive stars are also very hot, and this system is no exception: its main star is a type B star that is more than three times hotter than the Sun,” said the university astronomer. from Stockholm, Dr Markus Janson and his team. colleagues.

“Due to its intense temperature, it emits large amounts of ultraviolet radiation and X-rays.”

“The large mass and heat of this type of star has a strong impact on the surrounding gas, which should oppose the formation of the planets. In particular, the hotter a star, the more high-energy radiation it produces, which accelerates the evaporation of surrounding matter. “

This SPHERE image shows the most massive star pair hosting planets to date, b Centauri, and its giant planet b Centauri b.  Image credit: ESO / Janson et al.

This SPHERE image shows the most massive star pair hosting planets to date, b Centauri, and its giant planet b Centauri b. Image credit: ESO / Janson et al.

Astronomers observed the system with the VLT’s SPHERE instrument in 2019 and 2021 as part of the B-star Exoplanet Abundance Study (BEAST).

They also examined archival data and found that planet b Centauri b had been photographed over 20 years ago by ESO’s 3.6m telescope, although it was not recognized. like a planet at the time.

“The planet of b Centauri is an alien world in a completely different environment from what we experience here on Earth and in our solar system,” said Gayathri Viswanath, a PhD. 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 greater.

b Centauri b is 10 times more massive than Jupiter, making it one of the most massive planets ever discovered.

In addition, it orbits the mother stars at a distance of 560 AU (100 times the distance from Jupiter to the Sun) – one of the widest orbits ever discovered.

“This great distance from the center pair of stars could be the key to the planet’s survival,” the researchers said.

The team’s article was published this week in the journal Nature.

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Mr. Janson et al. 2021. A giant large orbiting planet in the high mass binary system b Centauri. Nature 600, 231-234; doi: 10.1038 / s41586-021-04124-8


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