READING THE DIAGRAM
The world of substellar objects
A number of distinct regimes can be seen in the substellar population: terrestrial worlds, ice giants and gas giants, and brown dwarfs. Brown dwarfs, which lack sustained core fusion, show a near-constant radius trend caused by increasing gravitational compression; stellar objects demonstrate increasing radii due to hydrostatic equilibrium with core radiation pressure
Dashed lines show equal mean bulk density, using R/R⊕ = [(ρ⊕/ρ)(M/M⊕)]⅓. Guides show 0.1, 1, 5.51, 10 and 100 g/cm³. They are geometric guides, not interior models or fitted population trends.
Example datasets for plotting object types; this selection does not representa complete census. Missing error bars mean uncertainty was not transcribed, not zero uncertainty. Densities are derived from central values; uncertainties and correlations not shown.