Summary edit

Adding material of density d to a planet of density D and radius R until it has radius r results in a planet with density:

${\displaystyle {\frac {(D-d)(4\pi /3)(R^{3})+(d)(4\pi /3)(r^{3})}{(4\pi /3)(r^{3})}}=(D-d)(R^{3})\cdot {\frac {1}{(r^{3})}}+d}$

The green lines are:

0.5-0.9: Rock and Iron: (3.6-3.34*1.45)*(0.5^3)*(r^-3) + 3.34*1.45

D=3.6, d=3.34*1.45, R=0.5

0.9-1.5: Rock and degenerate Iron: (4.8-3.34*2)*(0.9^3)*(r^-3) + 3.34*2

D=4.8, d=3.34*2, R=0.9

The blue line is:

1.5-4: Water: (6.1-1.15)*(1.48^3)*(r^-3) + 1.15

D=6.1, d=(1+0.15) R=1.48

The purple line is:

4-6: Water + Methane: (1.4-(0.782))*(4.11^3)*(r^-3) + 0.782

D=1.4, d=(0.682+0.1), R=4.11

The red line is:

6-10.5: Water + Methane: 0.005*r^3-0.0942857*r^2+0.613571*(r) - 0.337714 (Cubic fit)

The orange line is:

10.5-30: Hydrogen: (1.5-0.0708)*(10.5^3)*(r^-3) + 0.0708

D=1.5, d=0.0708, r=10.5

The yellow lines are:

2-6: Giants: (7-0.522)*(2^3)*(r^-3) + 0.522

D=4, d=(0.422+0.1), R=2.7

6-11.5: Giants: 0.00333*r^3-0.0632143*r^2+0.375595*r + 0.0517143 (Cubic fit)

See also:

• File:Exoplanet Density-Radius Scatter.png
• File:Planetary interior structure.png
• File:Water world interior structure.png
• File:Gas Giant interior structure.png
• File:Exoplanet Escape velocity-Radius Scatter.png
• File:Exoplanet Gravity-Radius Scatter.png
• File:Exoplanet Orbits.png
• File:Exoplanet systems.png
• File:Rapidly spinning planet.gif

Created with Matplotlib

Licensing edit

I, the copyright holder of this work, release this work into the public domain. This applies worldwide. In some countries this may not be legally possible; if so: I grant anyone the right to use this work for any purpose, without any conditions, unless such conditions are required by law.