Impossible Planet Discovered; Is that you, Gallifrey?
International astronomers based at the University of Arizona have recently discovered a planet that just simply shouldn’t be where it is. The planet, currently named HD 106906 b, is a large exoplanet, estimated to be approximately eleven times the size of Jupiter. It is a gas giant, located within the constellation Crux. HD 106906 b is estimated to be about 13 million years old, which makes the Earth about 350 times older at its believed age of 4.5 billion years. Doesn’t sound too strange at first glance, does it? Here’s where the numbers start looking odd.
HD 106906 b is about 650 Astonomical Units away from its host star, a distance 20 times greater than the distance between Neptune and our Sun. One Astronomical Unit, or AU, is roughly the distance between the Earth and the Sun. This is a total distance of 60,421,274,745 miles. Accepted theories for planet formation don’t fully explain how a gas giant as large as HD 106906 b can form that far away from its host star.
Under current theories, planetary systems start as a disk of gas and dust rotating in one direction around a star. As gravity causes the cloud to contract, irregular portions of the gas and dust cloud clump together. A star will begin to form at the center of the disk, and it’s gravity will cause the clumps and larger particles to drift toward the center. The clumps will add more mass and shift around in the disk until they balance themselves gravitationally around the center in stable orbits. As each orbit begins to define itself, the ‘planetesimals’ collide with more matter and add to their mass, which adjusts their orbit even more. The type of planets that form ultimately depend on the matter available within the orbit and temperature conditions.
Now, this process obviously takes a long time to occur, which means that planets should be pulled relatively close to the start they’re orbiting by the time the process is complete, assuming I’m understanding the theory correctly. So astronomers are collectively baffled about how a planet the size of HD 106906 b can possibly form at 650 AUs from its host star.
Another theory suggests that giant plants can form when the protoplanetary disk suddenly collapses. The problem with this theory is that primordial disks rarely have enough mass far from the center to allow a planet like HD 106906 b to form.
Vanessa Bailey, the University of Ariziona fifth-year graduate student who led the research, has suggested another hypotheses, which says that the planet may have formed in a manner similar to a binary star system.
A binary star system can be formed when two adjacent clumps of gas collapse more or less independently to form stars, and these stars are close enough to each other to exert a mutual gravitation attraction and bind them together in an orbit,” Bailey explained. “It is possible that in the case of the HD 106906 system the star and planet collapsed independently from clumps of gas, but for some reason the planet’s progenitor clump was starved for material and never grew large enough to ignite and become a star.
She goes on to say that one problem with this scenario is that the two stars in a binary system usually don’t have a mass ratio of any more than 10-to-1.
In our case, the mass ratio is more than 100-to-1,” she continued. “This extreme mass ratio is not predicted from binary star formation theories – just like planet formation theory predicts that we cannot form planets so far from the host star. Systems like this one, where we have additional information about the environment in which the planet resides, have the potential to help us disentangle the various formation models,” Bailey added. “Future observations of the planet’s orbital motion and the primary star’s debris disk may help answer that question.
Looks like just when we think we have a theory hammered out, the universe has to throw us a curveball to prove that we really don’t know enough. The hope of the team of astronomers is that further investigation into this planet and the surrounding area will yield even more information on how planets, solar systems, and galaxies form.
In light of the events of the recently-aired 50th anniversary episode of the popular TV show Doctor Who, a petition exists to rename HD 106906 b “Gallifrey.”
Looks like Peter Capaldi’s search for the missing planet Gallifrey is over before his season even begun.
You can sign the petition to officially change the impossible planet’s name to Gallifrey by clicking HERE.