One of the most beautiful things in science is that no matter how much we know about the universe we still get surprises which send us back to the drawing board. Exoplanet HD 106906b is one of those surprises. It’s a huge planet that shouldn’t exist, but not only does it, astronomers think it may also have a ring around itself like a super-Saturn.
HD 106906b, 300 light-years from Earth, is 97 billion kilometers (60 billion miles) from its host star, almost 22 times further than Neptune is from the Sun, and its orbital plane is tilted at an angle of 21 degrees from the inner planetary system. According to our planetary models, the exoplanet cannot have formed there, so when it was discovered scientists assumed it had been kicked out by the inner part of its star system.
Using the Gemini Planet Imager and the Hubble Space Telescope, researchers were able to see a highly disrupted system. The system has a debris disk extending between 7 billion to over 70 billion kilometers from the star (5 billion to over 46 billion miles). The ring is highly asymmetric with the side on the side of HD 106906b being thin and extending almost to the planet, while the disk on the other side of the star appears to be thick and significantly shorter.
Astronomers think that this is an indication that the entire system is highly perturbed, and it is possible that when the planet was pushed out from the inner star system it stole comets and materials from the debris disk, which now orbit around HD 106906b.
“We think that the planet itself could have captured material from the comet belt, and that the planet is surrounded by a large dust ring or dust shroud,” said Paul Kalas, lead author of the study, in a statement. “We conducted three tests and found tentative evidence for a dust cloud, but the jury is still out.”
Two direct images of the cometary dust and exoplanet surrounding the young star HD 106906. The wider field in blue shows Hubble Space Telescope data where the star’s blinding light is artificially eclipsed (gray circular mask), by Paul Kalas, UC Berkeley
As far as astronomers can tell at the moment, the area closest to the star has been cleared of debris, which is a possible indication that a massive planet is yet to be observed in the system and may have been responsible for disrupting the system. The planet will have to be significantly more massive than HD 106906b to have done so, which is already quite heavy at 11 times the mass of Jupiter.
The system is very young, with the star HD 106906 being only 13 million years old, and some scientists think that our primordial Solar System was very similar, with Jupiter kicking another planet out. A deeper understanding of this system and similar ones could give us interesting insights into the formation of our own system.
The research, which is published in the Astrophysical Journal, is not definite proof of HD 106906b being an exiled super-Saturn though. The team stresses in the paper that significant follow-up work is necessary to validate and thoroughly model the system.