# Are there any planets or moons denser than Earth?

Earth has the highest density out of all planets, planetoids and moons of our planetary system, and also has a higher density than the Sun. Do we know any exoplanets or moons denser than Earth?

I feel it's a cheap answer but heavy Jupiters can get much denser than Earth because planets with Jupiter's mass stop adding size as they add more mass. A planet with Jupiter's size and 10-12 times Jupiter's mass would be over twice Earth's density.

As far as Earth-like planets, there's a cool property of terrestrial planets, more mass means more tightly packed in their cores. Basically a similar effect to the heavy Jupiters but not as pronounced. If you double the mass and keep the element ratio the same, the density should increase. For example, a planet like Mercury with a very high iron content, but much greater mass should easily surpass Earth's density.

Kepler 10b, appears to be a super-earth and its estimated density is greater than Earth's at 5.8 ± 0.8 g/cm3. It has a mass of about 3.7 Earths. The ± 0.8 g/cm3 offers some room for uncertainty, but some of the more massive terrestrial planets should be more dense than Earth.

I'd take this list with a grain of salt, but you can sort by density.

Kepler 131c which you mention appears to be a super Earth but its mass has a high margin for error. I would add that a mass 8 times that of Earth and a radius smaller than Earth is probably impossible, so I'm highly skeptical of some of those numbers.

• What density are you seeing there? I see 0.026 $M_J$ and 0.075 $R_J$ and I assume $J$ stands for Jupiter. What density does that work out to?
• NASA page on Kepler-131c: exoplanets.nasa.gov/exoplanet-catalog/5941/kepler-131-c . Those numbers correspond to a density of $76.4\text{g}/\text{cm}^3$, or 13.9 times the average density of the Earth. That makes no sense, as noted in Mass-radius relations and core-envelope decompositions of super-Earths and sub-Neptunes. There's something wrong with the reported mass, the reported size, or both. The linked article gives the uncertainty in the mass of Kepler-131c. It's very large. Feb 6 '20 at 16:05