14 DAY TRIAL // While analyzing several hundred confirmed extrasolar planets, astronomers found that gas giants seem to prefer orbiting their parent stars in specific orbits, while leaving others entirely unoccupied. A new study now provides an answer to this mystery.
Jupiter- or Saturn-like exoplanets occupy these preferred regions of space around their parent stars in mature systems, experts say. They now provide a plausible explanation for the phenomena that may lead to this state of affairs.
The real issue here is that, theoretically, exoplanets should be disposed on all orbits around their respective stars, similar to how things occur in our own solar system. Experts now say that this does not happen in most systems because of the high-energy radiations released by the parent star in its infancy.
“Our results show that the final distribution of planets does not vary smoothly with distance from the star, but instead has clear ‘deserts' – deficits of planets – and ‘pile-ups' of planets at particular locations,” Ilaria Pascucci explains.
The expert holds an appointment as an assistant professor at the University of Arizona (UA) Lunar and Planetary Laboratory (LPL). She conducted the work with colleague Richard Alexander, from the University of Leicester, in the United Kingdom, PhysOrg reports.
“Our models offer a plausible explanation for the pile-ups of giant planets observed recently detected in exoplanet surveys,” Alexander argues. He says that forming stars tend to release high-energy radiations in specific patterns, which literally carve holes in the protoplanetary disks around them.
These disks contain all the matter available for planetary formation within that star system. If bands are cleared within its structure, then the orbits those bands correspond to will be left empty. In special scenarios, however, it is possible for planets to move into those orbits later on, through migration.
“For a long time, it was assumed that the process of accreting material from the disk onto the star was enough to explain the thinning of the protoplanetary disk over time. Our new results suggest that there is another process at work that takes material out of the disk,” Pascucci says of the radiation bombardment.
“The disk material that is very close to the star is very hot, but it is held in place by the star's strong gravity. Further out in the disk where gravity is much weaker, the heated gas evaporates into space,” Alexander concludes.