(ORDO NEWS) — A new model that takes into account the interplay of forces affecting newborn planets could explain two puzzling phenomena that have been repeatedly observed among the 3,800 planetary systems cataloged to date.
One mystery has to do with the rarity of exoplanets with a radius roughly 1.8 times Earth’s. NASA’s Kepler spacecraft observed planets of this size about 2-3 times less often than super-Earths with radii about 1.4 times the radius of the Earth, and mini-Neptunes with radii about 2.5 times the Earth’s.
The second mystery lies in the presence of planetary systems in which there are planets of the same size that are in orbital resonance. These include TRAPPIST-1 and Kepler-223, which have planetary orbits close to musical harmony.
Scientists have explained these phenomena by creating models for the formation and evolution of planetary systems.
They recreated the first 50 million years of planetary systems using the planetary migration model. In the model, the protoplanetary disks of gas and dust that give rise to young planets also interact with them, pulling them closer to their parent stars and “trapping” them in resonant orbital chains.
These chains are broken within a few million years when the disappearance of a protoplanetary disk causes an orbital instability resulting in two or more planets colliding with each other.
Planetary migration models have been used to study planetary systems that have retained their resonant orbital chains.
“The migration of young planets towards their stars creates overpopulation and often leads to catastrophic collisions that deprive the planets of their hydrogen-rich atmosphere,” the researchers said.
“This means that giant impacts like the one that formed our Moon are probably a common result of planetary formation.”
Based on their findings, the researchers made predictions that could be tested by the James Webb Space Telescope. Scientists suggest that some of the planets, about twice the size of the Earth, will retain their original atmosphere, rich in hydrogen, and will have water.
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