Missing planets twice Earth's may point to migrating worlds

[Admin]

New supercomputer simulations help explain why exoplanets about twice the of Earth are rare.

Missing planets twice Earth's may point to migrating worlds : Read more

 

[rod]

I note from the article. "However, astronomers know that the protoplanetary disk that permits this migration does not last forever. As the young star begins to generate more energy, its radiation wind blows the disk away; as the disk dissipates the planets become destabilized, prompting collisions between worlds and smaller protoplanets. "The migration of young planets towards their host stars creates overcrowding and frequently results in cataclysmic collisions that strip planets of their hydrogen-rich atmospheres," Izidoro said in a statement. "That means giant impacts, like the one that formed our moon, are probably a generic outcome of planet formation." The simulations found that the migration of planets, the subsequent orbital destabilization and the loss of thick planetary atmospheres all conspires to preferentially create two populations of planets: the super-Earths that are rocky and dry, and the mini-Neptunes that did not migrate as far inward and are able to retain their thick atmospheres of hydrogen and water."

Exoplanet sites like this confirm 5271 now, The Extrasolar Planets Encyclopaedia (exoplanet.eu)

The vast majority show no disc present in these planetary systems so assumptions must be made about explaining their origins. I did a MS SQL query and found 587 exoplanets listed with earth radii 0.8 to 1.4 earth radii size. The article stated, "Exoplanets can come in a variety of sizes and masses. If you were to plot on a graph how many planets of each size astronomers have discovered, you'd find two peaks: one at 1.4 times Earth's radius, and another at 2.4 times Earth's radius. Between them is a dip or valley, at around 1.8 times the radius of Earth, signifying the relative scarcity of planets of that size."

When it comes to 1.4 to 2.4 earth radii size, I found 1200, so the slicing and dicing for the model reported is fine-tuned

Concerning planet migration inwards into the parent star, other reports now confirm exoplanets like WASP-12 b fall into their host star in about 3 million years from present, so are not stable over millions or billions of years (into the future). What we do see in these planetary systems is unstable orbits in the present.

Aging Ungracefully, Sky & Telescope 145(1):14-19, 2023. January 2023 issue.

"IMMINENT DEMISE If planets stayed put until their stars swelled to engulf them, then the hot Jupiter WASP-12b would have about 2 billion years in its future. But observations reveal that the planet’s orbit is decaying rapidly — in only 3 million years, it will plunge into the star."

My observation. This arxiv.org report confirms WASP-12 b shows orbital decay. Examining the orbital decay targets KELT-9 b, KELT-16 b and WASP-4 b, and the transit-timing variations of HD 97658 b, https://arxiv.org/abs/2211.05646, 10-Nov-2022. "Tidal orbital decay is suspected to occur especially for hot Jupiters, with the only observationally confirmed case of this being WASP-12 b..."

Apparently inward migration in exoplanet systems can also result in planets falling into the parent stars on short time scales.