Courses › The Universe from Scratch › Lesson 5
Seven worlds around one star · premieres Wednesday, October 28
Some forty light-years away there is a tiny star with a record: seven Earth-sized planets. It is called TRAPPIST-1. Today we'll see why this system is one of the most studied in astronomy, and what we really know about its planets.
In the image, the periods, sizes and masses are the measured ones. But each planet's appearance is invented: we don't know what its surface looks like. The orbits are drawn circular and in the same plane, which is a good approximation but not exact, and the star is drawn about nine times larger than it is.
| Figure | Value | Source |
|---|---|---|
| Distance | 12.43 pc ≈ 40.5 light-years | NASA Exoplanet Archive (composite table, 5 Oct 2026) |
| Star | 0.0898 M☉; 0.1192 R☉ (≈1.19 Jupiter radii); 2,566 K | Agol et al. 2021, Table 7 |
| Periods | b 1.51 d … h 18.77 d | Agol et al. 2021, Table 6 |
| Distances | 0.01154 to 0.06189 AU (Mercury: 0.387 AU) | Agol et al. 2021; computed by the template |
| Masses from transit variations | 0.326 to 1.374 M⊕ | Agol et al. 2021 |
| Period ratios | 1.603; 1.672; 1.507; 1.509; 1.342; 1.520 (≈8:5, 5:3, 3:2, 3:2, 4:3, 3:2) | Computed by the template |
| Habitable zone | e, f and g in the conservative; d in the optimistic (extrapolation: the star is below the 2,600 K range) | Kopparapu et al. 2014, computed by the template |
| JWST | b: 490 ± 17 K, no thick atmosphere; c: 380 ± 31 K or 369 ± 23 K, no dense CO₂ atmosphere | Zieba et al. 2023; Gillon et al. 2026 |
They are Solaris Core Blender templates, built from measured data. You can download them, change the camera and make your own images.
See templates