TRAPPIST-1 g
TRAPPIST-1 g is a terrestrial planet orbiting TRAPPIST-1 in the constellation Aquarius. It lies about 41 light-years from Earth and was discovered in 2017 using the transit method. It orbits within the habitable zone of its star — the region where liquid water could exist on a planet's surface.
How Big Is TRAPPIST-1 g?
TRAPPIST-1 g has a radius of 1.13 times that of Earth. Its mass is 1.3 times that of Earth, giving it a density of 5.06 g/cm³ — comparable to rocky planets like Earth (5.51 g/cm³).
Is TRAPPIST-1 g in the Habitable Zone?
TRAPPIST-1 g orbits inside the conservative habitable zone of TRAPPIST-1 — the region where a rocky planet could sustain liquid water on its surface. This makes it one of the most interesting known exoplanets in the search for life.
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 ›
Temperature on TRAPPIST-1 g
TRAPPIST-1 g receives 0.25 times the stellar energy that Earth gets from the Sun.
Orbit and Year Length
A year on TRAPPIST-1 g — one full orbit around TRAPPIST-1 — lasts 12.4 Earth days, shorter than Mercury's 88-day year. It orbits at an average distance of 0.047 AU — closer to its star than Mercury is to the Sun.
How Was TRAPPIST-1 g Discovered?
TRAPPIST-1 g was discovered in 2017 using the transit method, with observations from Multiple Observatories.
The transit method watches a star for the tiny, regular dip in brightness that occurs when a planet crosses in front of it. The depth and timing of these dips reveal the planet's size and orbital period.
How Far Away Is TRAPPIST-1 g?
TRAPPIST-1 g is 40.5 light-years (12.4 parsecs) from Earth. Light arriving here tonight left the planet around the year 1986. A probe traveling at the speed of Voyager 1 — about 17 km/s, the fastest outbound spacecraft ever launched — would need roughly 712,800 years to make the journey.
Earth Similarity Index
The Earth Similarity Index (ESI) scores how physically similar a planet is to Earth, from 0 to 1, based on radius, density, escape velocity and surface temperature. TRAPPIST-1 g scores 0.58, ranking #160 of 5,565 planets with a known ESI. For reference, Mars scores about 0.70.
The Host Star: TRAPPIST-1
TRAPPIST-1
- Surface temperature
- 2,566 K (Sun: 5,772 K)
- Mass
- 0.09 M☉
- Radius
- 0.12 R☉
- Luminosity
- 0.0006 L☉
The TRAPPIST-1 Planetary System
TRAPPIST-1 g is one of 7 known planets in the TRAPPIST-1 system. Its siblings:
- TRAPPIST-1 b (Terrestrial)
- TRAPPIST-1 c (Terrestrial)
- TRAPPIST-1 d (Terrestrial)
- TRAPPIST-1 e (Terrestrial)
- TRAPPIST-1 f (Terrestrial)
- TRAPPIST-1 h (Terrestrial)
TRAPPIST-1 g — Complete Data
| Radius | 1.129 Earth radii (0.101 Jupiter radii) |
|---|---|
| Mass | 1.32 Earth masses (0.004 Jupiter masses) |
| Density | 5.06 g/cm³ (Earth: 5.51) |
| Orbital period | 12.35 days |
| Orbital distance | 0.047 AU |
| Stellar irradiation | 0.25× Earth |
| Earth Similarity Index | 0.58 |
| Distance from Earth | 40.5 light-years (12.4 parsecs) |
| Constellation | Aquarius |
| Discovery method | Transit |
| Discovery facility | Multiple Observatories |
| Discovery year | 2017 |
Data: NASA Exoplanet Archive, last updated 2022-11-14. Earth Similarity Index: PHL @ UPR Arecibo.
Frequently Asked Questions About TRAPPIST-1 g
Is TRAPPIST-1 g habitable?
TRAPPIST-1 g orbits within the habitable zone of TRAPPIST-1, the region where liquid water could exist on a planet's surface. It sits in the conservative habitable zone — the most promising region for habitability. Whether it is actually habitable depends on its atmosphere and composition, which remain unknown.
How far away is TRAPPIST-1 g?
TRAPPIST-1 g is about 41 light-years from Earth in the constellation Aquarius. A spacecraft traveling as fast as Voyager 1 (about 17 km/s) would need roughly 712,800 years to get there.
How big is TRAPPIST-1 g compared to Earth?
TRAPPIST-1 g has 1.13 times the radius of Earth and about 1.3 times its mass.
How long is a year on TRAPPIST-1 g?
One orbit around TRAPPIST-1 takes 12.4 Earth days — short enough that 30 of its years would fit into one Earth year.
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