A planet eleven times as big as Jupiter has been discovered orbiting a star at a distance of 650 astronomical units. That’s 650 times as far from its star as Earth is from our own star. Never have we discovered a planet to be orbiting a star at so nearly great a distance.
The planet is called HD 106906 b, and it’s making astronomers scratch their heads. It doesn’t conform to planetary formation theory, the usual run of which is that planets are mainly just asteroids that got caught in a nascent star’s disc of gas and dust. In order for that to happen, they have to be close. 650 AU is not close enough. Planet HD 106906 b is exemplary of planets that defy this model.
Yet it doesn’t conform to binary star formation theory, either. In binary star formation, two masses of gas and dust collapse independently, develop gravity, and eventually form a mutual orbit around each other. It has been suggested that planet HD 106906 b could actually have started out that way. The problem with the hypothesis is that it lacks the necessary mass to borrow the rules, as it were, from binary star formation theory. Typically binary stars are no more variant in size than a ratio of 10 to 1. Planet HD 106906 b is about 100 times smaller than its star — a very respectable proportion, but not star-like.
It’s a strapping young planet, about 13 million years old. Compare that to Earth’s 4.5 billion years. The debris disc can even still be detected (as seen in the artist rendering above.) Astronomers will use this discovery to aid in reformulating theories about how stars and planets form in relationship to one another.
The images were captured by the Earth-bound Magellan telescope — in the Atacama Desert in Chile — and its position was confirmed by the Hubble telescope.