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Saturday, June 15, 2024 | Back issues
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New planet discovered in the massive b Centauri two-star system

Scientists discovered a planet in a two-star system so extreme that it was previously thought unlikely that a planet could form there.

(CN) — Scientists with the European Southern Observatory discovered a planet in the hottest and most massive planet-hosting star system ever recorded.

The two-star system where the planet is located, known as HIP 71865, or b Centauri, sits within the constellation Centaurus about 325-light years from Earth.

At six times the mass of our own sun, the system is so massive, and so hot, that until being photographed by the ESO’s Very Large Telescope, many experts didn’t believe a planet could exist there. The new discovery shows that it is possible; the planet was found orbiting one of the system’s two stars at around 100 times the distance between Jupiter and the sun.

A team of astronomers from across Europe described the newly identified planet in a study published Wednesday in the journal Nature.

“Finding a planet around b Centauri was very exciting since it completely changes the picture about massive stars as planet hosts,” Markus Janson, an astronomer at Stockholm University and first author of the study, said in a related statement.

The planet, dubbed b Centauri b, hosts an extremely hostile environment by any earthly measure. At 10 times the mass of Jupiter, b Centauri b is among the most massive planets ever discovered. It also moves in one of the widest orbits ever recorded — the vast distance between the planet and the system’s two stars may play an important role in the planet’s survival. The discovery proves that planets can indeed form and survive in environments that were previously thought to be too extreme.

“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,” explained co-author 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 bigger.”

Massive stars are typically very hot, and that holds true for the b Centauri system. Its main star is classified as B-type, meaning it has a mass between 2 to 16 times that of Earth’s sun, with surface temperatures ranging from around 17,500 to 53,500 degrees Fahrenheit. Temperatures that extreme result in large doses of ultraviolet and X-ray radiation as well, making it all the more inhospitable by human standards.

According to the authors, the star’s extreme mass and heat should have a significant impact on surrounding gases in the system, which would make planet formation difficult. Hotter stars produce more high energy radiation, causing nearby matter to evaporate quicker, thus leaving less raw material dispersed around the system for planet formation.

“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,” Janson concluded.

The authors hypothesize that such a planet is unlikely to have formed in its current location, and may have actually formed elsewhere and been transported through dynamic interactions with other stellar objects, or through gravitational instability. By studying these types of extreme systems where planet formation was thought to be rare, if not impossible, scientists believe they can gain a deeper understanding of the process by which planets are born.

“Planet formation occurs around a wide range of stellar masses and stellar system architectures,” explained the authors in the study. “An improved understanding of the formation process can be achieved by studying it across the full parameter space, particularly towards the extremes.”

For their measurements, the team relied on ESO’s Very Large Telescope, located in Chile, and an advanced imaging tool attached to it known at the Spectro-Polarimetric High-contrast Exoplanet Research instrument, or SPHERE. Astronomers have previously imaged several planets located outside our solar system, known as exoplanets, using SPHERE. During their research, the authors found that the planet in b Centauri had been imaged more than two decades prior using the ESO 3.6m telescope, though at the time experts couldn’t confirm that it was actually a planet.

In the future, researchers will have even more powerful tools at their disposal, such as the ESO’s upcoming Extremely Large Telescope, or ELT, which is set to begin operation by the end of the decade. Every new tool brings the promise of new, more astounding discoveries, and the authors hope ELT will help shine some light on the features and origin of the newly discovered planet.

“It will be an intriguing task to try to figure out how it might have formed, which is a mystery at the moment,” Janson said.

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