LHS 3154 and it's Giant Planet
Until recently, the idea that a very low mass star could create a very large planet would have raised more than eye brows amongst those who study exoplanets and how they formed, even maybe a chuckle, but the more we search out from our Solar System and see the diversity just in our own local part of the galaxy, the more it challenges these and other assumptions about how our own Solar System came to be.
LHS 3154b is a Sub Neptune planet around 13.2 times the mass of our Earth (Neptune being just over 17 times the mass), and while Sub Neptune exoplanets are turning up pretty much everywhere, this one orbiting so close around it's barely M type star, is a bit of a confusion, how did a planet that's 35% the mass of it's parent star get to exist.
For comparison, Jupiter is .1% the mass of our Star.
The amount of matter required to make this small star, would seem to negate such a large planet forming, and when we look at many M type red dwarf stars, that's what we see, smaller rocky worlds.
The team spent much time trying to model what could possibly have created it, and in the end came to the conclusion there was either a lot more mass in the disk than was expected, or that the disk was surrounded by a very large pool of material that had been sucked in during the formation.
The team ruled out the idea of capture due to the orbital pattern of the planet, expecting a much more elliptical orbit had it been so (although, there are many processes that could have changed the orbit over billions of years that M type stars exist).
Since the team found the initial wobbling of the planet, TESS has been and confirmed the existence of the planet as have a few other orbital telescopes. It would seem the process of planet creation is very common, but also very unique to the system, and doesn't always follow the same rules as any other star system.
