Astronomers have discovered a huge exoplanet orbiting the binary star system HD 129116, also known as b Centauri. The two stars are so hot and big that researchers previously thought that a planet cannot exist around them.
The binary star system is located in the constellation Centauri, about 325 light-years from our own solar system. Its main star is three times hotter than our sun, and along with its partner star, they have a combined weight of about 6 to 10 suns. Up until now, no planet has been found orbiting a star with a mass more than three times the mass of the sun. The new exoplanet b Centauri b seems to be a gas giant with a similar composition to Jupiter, but its mass is at least 10 times that of this planet. It is one of the largest exoplanets discovered so far. The distance between Centauri b and its star is 52 billion miles (~80 billion km), one of the widest orbits ever detected.
“Finding a planet around b Centauri was very exciting since it completely changes the picture about massive stars as planet hosts… 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” explains lead study author Markus Janson, an astronomer at Stockholm University, Sweden.
The stars of b Centauri are just 15 million years old, compared to our sun’s 4.6 billion years. “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,” co-author Gayathri Viswanath, said in a statement. “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.”
Astronomers have yet to figure out how b Centauri b originated, and they will now work to unravel the origin story of this unlikely system. Scientists called this a “mystery for the moment” that will be “an intriguing task to try to figure out”. They admitted that the finding poses a challenge to the existing models and they will have to rethink the parameters around planet formation.
In the last few decades, scientists have confirmed the existence of thousands of exoplanets, revealing an astonishing variety of conditions under which planets can form. No matter where astronomers look, they always seem to find planets – even in places they didn’t think possible.
