Out in Space Lies a Mysterious, Massive Planet That Shouldn't Exist

[Judi Lynn]

Defying our theories of planetary formation, this "forbidden" world orbits a quiet little star.

Monisha Ravisetti
Feb. 24, 2023 2:29 p.m. PT

About 285 light-years from our solar system lies a lovely, minimalist cosmic neighborhood. Its "sun," you might say, is a particularly small, glowing crimson body named TOI-5205 -- a red dwarf. And submerged within the void of space, we've now located exactly one planetary friend of TOI-5205, according to a paper published this week in The Astronomical Journal. Scientists call it TOI-5205b. Yes, that moniker is based on formality, but you must admit it's also kinda cute.

. . .

It's pretty typical for red dwarfs to anchor planets (often several), because these stellar bodies are only about half as hot as the sun and have very low luminosities, yet are known to average extremely long lifespans. Even TOI-5205 is measured to be about 3,500 Kelvin (3,227 degrees Celsius), in contrast to our 5,800 Kelvin (5,526 degrees Celsius) sun. However, there are two peculiar aspects of TOI-5205 and TOI-5205b's companionship.

First off, red dwarfs aren't expected to host gas giant planets -- but that's exactly what TOI-5205b is. Second, and most importantly, sunlike stars in general are usually thought to host planets significantly tinier than themselves.

"The host star, TOI-5205, is just about four times the size of Jupiter, yet it has somehow managed to form a Jupiter-sized planet, which is quite surprising!" Shubham Kanodia, an astronomer at the Carnegie Institute of Science and co-author of the study, said in a statement. "Based on our nominal current understanding of planet formation, TOI-5205b should not exist."

More:
https://www.cnet.com/science/space/out-in-space-lies-a-mysterious-massive-planet-that-shouldnt-exist/