The TRAPPIST-1 System
TRAPPIST-1 is a planetary system in the constellation Aquarius hosting 7 confirmed exoplanets, about 41 light-years from Earth. 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.
How far away is TRAPPIST-1?
TRAPPIST-1 is about 41 light-years from Earth in the constellation Aquarius.
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