Can a planet have 10x Earth mass, 4x Earth gravity and support intelligent life?

If $R$ is the planet's radius and $\rho$ is the planet's average density, then its surface gravity is $\propto \rho R$ and its mass is $\propto \rho R^3$.

Let's measure in units where the Earth's radius and average density are both 1. Then for Dekuuna we have $\rho R=4$ and $\rho R^3=10$. Therefore we get \begin{align} R &= \sqrt{\frac{\rho R^3}{\rho R}} = \sqrt{\frac{10}{4}} \approx 1.6\\ \rho &= \sqrt{\frac{(\rho R)^3}{\rho R^3}} = \sqrt{\frac{64}{10}} \approx 2.5 \end{align} So that planet would have a radius of about 1.6 times the Earth's radius and an average density of about 2.5 times the Earth's average density. The radius is definitely possible, and I think the density should be, too. To begin with, the higher radius and mass would already cause an increased density, although that alone will not get a factor 2.5. But then, the planet could have a relatively bigger core, and it might have more heavy elements in its core.

I also think 4 times earth gravity should not preclude the evolution of intelligent life.

posted almost 8 years ago

celtschk‭

341 reputation 24 102 42 10

I'm going to work off of celtschk's excellent answer, which correctly comes up with a radius of $\sim1.6 R_{\oplus}$ and a density of $\sim2.5\rho_{\oplus}$, where $_{\oplus}$ denotes Earth. If we look at the mass-radius curves of Mocquet et al. (2014), we see that the planet lies very close to the line for pure iron planets:

Some fun facts about iron planets:

• They're essentially just cores of terrestrial planets.
• They likely cannot hold water.
• They have no tectonic activity or magnetic field.
• They may be close to their parent star, meaning surface temperatures will be extremely high.

This doesn't seem like a very pleasant place for life.

posted almost 8 years ago

HDE 226868‭

586 reputation 61 463 77 49