According to a new study, the massive lonely extrasolar planet known as HD 106906b may have been flung-out of its solar system by another neighboring planet.
HD 106906b orbits its star at an extreme distance – about 16 times as far as Pluto is from the Sun. It’s approximately 11 times more massive than Jupiter. When the planet was discovered in 2015, astronomers suggested it may have formed on its own like a star, with its own disk of material. However, a new study published in the Astrophysical Journal has brought to light new evidence substantiating the kicked-out planet theory. [NASA’s Kepler Uncovers a Trove of New Planets]
Using the Gemini Planet Imager (GPI) and NASA’s Hubble Space Telescope, astronomers identified a lop-sided comet belt surrounding the star, suggesting that the belt had been stirred up by a planet. According to scientists, characteristics of the debris-belt suggest that planets formed within it. The team searched for another planet orbiting beyond the belt but found nothing.
It’s likely that HD 106906b was booted out of the inner solar system passing through the belt of debris. Scientists think more detailed observations should show a system of debris from the belt associated with HD 106906b. But you might ask, how could such a large planet be booted deep into interstellar space?
The planets host star is a binary star system, consisting of two stars dancing in orbit around one another at less than half the distance Earth is from the Sun. Models have shown that planets are more likely to be kicked-out in a binary star system because of the unique gravitational jostling between the tightly orbiting hosts.
Although there is no direct evidence, scientists think that HD 106906b formed near or beyond the belt system, eventually migrating inward toward the chaotic binary environment until it was flung out by gravitational jostling on its way into deep space.
However, everything at this point is basically speculation, as many questions still remain. It’s not clear if HD 106906b is actually orbiting the assumed host star. Since the object was discovered only last year, scientists do not have enough observations to calculate its orbital parameters. Scientists also argue that the flung-out planet theory would require another large planet to substantiate the claims, which has not been found to date.
There is hope that other large planets may exist around the host star. HD 106906b is a young object and therefore still warm. Using near infrared imaging, astronomers are able to see the planet because of the heat it gives off. Larger, older and colder planets would likely remained undetected using this method.
“If we find another planet, HD 106906c, then we could be more specific about the history of the system,” said lead-author Paul Kalas from the University of California, Berkeley.