The TRAPPIST-1 System
TRAPPIST-1 is a planetary system in the constellation Aquarius hosting 7 confirmed exoplanets. 4 of its planets orbit within the habitable zone, where liquid water could exist on a planetary surface.
Size Comparison: The Planets of TRAPPIST-1
TRAPPIST-1: Star and Habitable Zone
TRAPPIST-1
- Surface temperature
- 2,566 K (Sun: 5,772 K)
- Mass
- 0.09 M☉
- Radius
- 0.12 R☉
- Luminosity
- 0.0006 L☉
Habitable zone of TRAPPIST-1: 0.019–0.053 AU (conservative: 0.025–0.050 AU), per Kopparapu et al. (2014). Earth orbits the Sun at 1 AU.
See the full interactive habitable-zone view in the Exoplanet Explorer app ›
All 7 Planets in the TRAPPIST-1 System
| Planet | Type | Orbit | Radius | ESI | Discovered |
|---|---|---|---|---|---|
| TRAPPIST-1 b | Terrestrial | 1.5 d | 1.12 R⊕ | 0.57 | 2016 |
| TRAPPIST-1 c | Terrestrial | 2.4 d | 1.10 R⊕ | 0.73 | 2016 |
| TRAPPIST-1 d HZ | Terrestrial | 4.0 d | 0.79 R⊕ | 0.91 | 2016 |
| TRAPPIST-1 e HZ | Terrestrial | 6.1 d | 0.92 R⊕ | 0.85 | 2017 |
| TRAPPIST-1 f HZ | Terrestrial | 9.2 d | 1.05 R⊕ | 0.68 | 2017 |
| TRAPPIST-1 g HZ | Terrestrial | 12 d | 1.13 R⊕ | 0.58 | 2017 |
| TRAPPIST-1 h | Terrestrial | 19 d | 0.76 R⊕ | 0.46 | 2017 |
Discovery History
The first planet found here, TRAPPIST-1 b, was discovered in 2016 using the transit method. The most recent addition, TRAPPIST-1 h, followed in 2017.
- 2016 — TRAPPIST-1 b (Transit)
- 2016 — TRAPPIST-1 c (Transit)
- 2016 — TRAPPIST-1 d (Transit)
- 2017 — TRAPPIST-1 e (Transit)
- 2017 — TRAPPIST-1 f (Transit)
- 2017 — TRAPPIST-1 g (Transit)
- 2017 — TRAPPIST-1 h (Transit)
Frequently Asked Questions About TRAPPIST-1
How many planets does TRAPPIST-1 have?
TRAPPIST-1 has 7 confirmed exoplanets. More may await discovery.
Are any planets in the TRAPPIST-1 system habitable?
4 planets in the system orbit within the habitable zone, where liquid water could exist. Actual habitability depends on atmospheres and composition, which are not yet known.
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