Page 1 of 1
SWaB: Ask Ethan: Are “super-Earths” really the most common planets in the Universe?
Posted: Sat Jan 22, 2022 11:11 pm
by notFritzArgelander
Re: SWaB: Ask Ethan: Are “super-Earths” really the most common planets in the Universe?
Posted: Sun Jan 23, 2022 4:35 am
by ThinkerX
This makes the risky assumption that terrestrial planets all have similar densities. Titan and Mars, for example, are roughly the same size, but differ substantially in mass (according to my admittedly shaky memory). Therefore, a large 'low density' 'super-Earth' could avoid becoming a 'Mini-Neptune.'
Okay...it's way past time for a new planetary classification scheme, one that can be introduced into what's left of the public school system without undo havoc...
Re: SWaB: Ask Ethan: Are “super-Earths” really the most common planets in the Universe?
Posted: Sun Jan 23, 2022 5:49 am
by notFritzArgelander
I’m not so sure that a low density super earth is terribly possible. At least not within the ice line. Mars is this side of the ice line while Titan is on the other.
Re: SWaB: Ask Ethan: Are “super-Earths” really the most common planets in the Universe?
Posted: Sun Jan 23, 2022 10:21 am
by ThinkerX
Earth to Mars density, then:
https://phys.org/news/2015-12-mars-earth.html
In terms of their size and mass, Earth and Mars are quite different. With a mean radius of 6371 km and a mass of 5.97×1024 kg, Earth is the fifth largest and fifth most-massive planet in the Solar System, and the largest of the terrestrial planets. Mars, meanwhile, has a radius of approximately 3,396 km at its equator (3,376 km at its polar regions), which is the equivalent of roughly 0.53 Earths. However, it's mass is just 6.4185 x 1023 kg, which is around 15% that of Earth's.
Might be an 'ice line' thing, might be something else.
Venus is closer, about 5% less dense than Earth.
Super-Earths in lower metallicity systems, hmm...could be say twice the size of Earth with only half the density. And have some interesting geologies.