Entering orbit…
| Yours | GJ 3138 d | |
|---|---|---|
| Mass | 9.30 × Earth | 10.5 × Earth |
| Radius | 3.18 × Earth | 3.23 × Earth |
| Density (composition) | 1.60 g/cm³ | 1.72 g/cm³ |
| Temperature | 155.8 K | 152.0 K |
| Starlight received | 0.08 × Earth | 0.10 × Earth |
| Star temperature | 4,450 K | 3,717 K |
Outside the synchronous orbit: slowly receding, like Luna (~cm per year).
Tidal braking locked the planet to its moon: one face forever moonward.
Tidal heat sustains a subsurface ocean over a rock seafloor: a strong candidate for life (Europa-like, 72/100).
Inside the synchronous orbit: it spiraled inward and was torn apart at the Roche limit (Phobos's fate).
Small and distant: a quiet, stable companion.