belbalady.net The number of confirmed exoplanets is 5,197 in 3,888 planetary systems, with another 8,992 candidates awaiting confirmation. The vast majority were particularly massive planets, ranging from gas giants the size of Neptune and Jupiter, which have a radius about 2.5 times the diameter of Earth.
Another statistically significant group is the rocky planets, which measure about 1.4 Earth radii (also known as ‘super-Earths’).
This is a mystery to astronomers, especially when it comes to the exoplanets discovered by the Kepler space telescope.
Of the more than 2,600 planets discovered by Kepler, there is a distinct dearth of exoplanets with a radius of about 1.8 times the diameter of Earth – referred to as the “Valley of the Radius”.
The second puzzle refers to neighboring planets of similar size in hundreds of planetary systems with symmetric orbits.
In a study led by the Fundamental Life Cycles of Volatile Elements in Rocky Planets (Clever) Project at Rice University, an international team of astrophysicists presented a new model that explains the interaction of forces acting on newborn planets that could explain these two puzzles.
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Hubble takes pictures of an 11-billion-year-old supernova a few hours after its initial explosion
Hubble takes pictures of an 11-billion-year-old supernova a few hours after its initial explosion
The research was led by Andre Isidoro, of NASA’s CLEVER Planets project. He was joined by planetary researchers from Clever Rajdeep Dasgupta and Andrea Isella, Helk Schleichting of UCLA, and Christian Zimmermann and Bertram Beech of the Max Planck Institute for Astronomy (MPIA).
As they describe in their paper, which appeared recently in Astrophysical Journal Letters, the team used a supercomputer to run a planetary migration model that simulated the first 50 million years of planetary system development.
In their model, protoplanetary disks of gas and dust also interact with the migrating planets, pulling them close to their parent stars and trapping them in resonant orbital chains.
Within a few million years, the protoplanetary disk disappears, breaking the chains and causing orbital instability that causes two or more planets to collide.
And in a paper appearing November 21, 2021 in Nature Astronomy, they used N-body simulations to show how a system called a “pea in a capsule” could retain its symmetrical orbital structure despite collisions caused by planetary migration. This allowed them to place constraints on the upper limit of collision and the mass of the objects involved.
Their results indicate that the collisions in the TRAPPIST-1 system were comparable to the impact that led to the creation of the Earth-Moon system.
“Migration of small planets toward their host stars creates overcrowding and often leads to catastrophic collisions that strip planets of their hydrogen-rich atmosphere. This means that giant impacts, such as the ones that formed our moon, are probably a general result of planet formation,” Isidoro said.
This latest research indicates that planets come in two different types, consisting of dry, rocky planets 50% larger than Earth (super-Earths) and water-ice-rich planets more than 2.5 times the size of Earth (junior Neptunes).
In addition, they suggest that a small portion of planets twice the size of Earth would retain their primordial hydrogen-rich atmosphere and would be rich in water.
According to Isidoro, these findings are consistent with new observations that the super-Earths and minor Neptunes are not just dry and rocky planets.
These findings present opportunities for exoplanet researchers, who will rely on the James Webb Space Telescope to make detailed observations of exoplanet systems.
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