Early planetary migration can explain missing planets: Study

tech.hindustantimes.com:

Computer simulations by Rice University scientists and their collaborators are the first to integrate a model of planet formation and evolution that explains two puzzling observations of exoplanets orbiting distant stars: the rarity of worlds about 1.8 times larger than Earth and the near-identical size of adjacent planets in hundreds of planetary systems.

One puzzle known as the "radius valley" refers to the rarity of exoplanets with a radius about 1.8 times that of Earth. NASA's Kepler spacecraft observed planets of this size about 2-3 times less frequently than it observed super-Earths with radii about 1.4 times that of Earth and mini-Neptunes with radii about 2.5 times Earth's. The second mystery, known as "peas in a pod," refers to neighboring planets of similar size that have been found in hundreds of planetary systems. Those include TRAPPIST-1 and Kepler-223, which also feature planetary orbits of near-musical harmony.

"I believe we are the first to explain the radius valley using a model of planet formation and dynamical evolution that self-consistently accounts for multiple constraints of observations," said Rice University's Andre Izidoro, corresponding author of a study published this week in Astrophysical Journal Letters. "We're also able to show that a planet-formation model incorporating giant impacts is consistent with the peas-in-a-pod feature of exoplanets."

Izidoro, a Welch Postdoctoral Fellow at Rice's NASA-fundedCLEVER Planets project, and co-authors used a supercomputer to simulate the first 50 million years of the development of planetary systems using a planetary migration model. In the model, protoplanetary disks of gas and dust that give rise to young planets also interact with them, pulling