Terrestrial planet · TRAPPIST-1

TRAPPIST-1 f

ExoplanetsHabitable-zone candidateDiscovered 2017

Scientific overview

TRAPPIST-1 f is a terrestrial planet orbiting TRAPPIST-1, completing an orbit every 9 days, about 41 light-years from Earth. It was discovered in 2017 using the transit method.

Host star

TRAPPIST-1

Spectral type

M8.0 V

Temperature

2,566 K

Mass

0.09 M☉

Planetary system — TRAPPIST-1 system

View the TRAPPIST-1 system (7 known planets).

Planet	Class	Radius (R⊕)	Period (d)	Distance (ly)
TRAPPIST-1 bTransit · 2016	Terrestrial planet	1.12	1.5108	41
TRAPPIST-1 cTransit · 2016	Terrestrial planet	1.1	2.4219	41
TRAPPIST-1 dTransit · 2016	Terrestrial planet	0.79	4.0492	41
TRAPPIST-1 eTransit · 2017	Terrestrial planet	0.92	6.101	41
TRAPPIST-1 fTransit · 2017	Terrestrial planet	1.05	9.2075	41
TRAPPIST-1 gTransit · 2017	Terrestrial planet	1.13	12.3524	41
TRAPPIST-1 hTransit · 2017	Terrestrial planet	0.76	18.7729	41

Discovery and detection

Detection method

Transit Method

Discovery year

2017

Habitability notes

TRAPPIST-1 f lies in the habitable zone of its star, the range of orbits where liquid water could in principle exist on a planet's surface. This makes it a candidate of interest for habitability studies — but lying in the habitable zone is not evidence that the planet is habitable or inhabited; its atmosphere and surface conditions remain unknown.

Knowledge connections

Child ofTRAPPIST-1
OrbitsTRAPPIST-1
Member of systemTRAPPIST-1 system
Discovered by methodTransit Method
Catalogued inNASA Exoplanet Archive
Habitable-zone candidateHabitable zone

Quick facts

Class: Terrestrial planet
Host star: TRAPPIST-1
Discovery method: Transit Method
Discovery year: 2017
Orbital period: 9.2075 d
Semi-major axis: 0.0385 AU
Eccentricity: 0.01
Radius: 1.05 R⊕
Mass: 1.04 M⊕
Density: 4.95 g/cm³ · derived
Equilibrium temp.: 218 K
Insolation: 0.37 S⊕
Distance: 41 ly

Density is derived from the archive mass and radius via ρ = M / (4⁄3·π·r³); all other values are catalogued measurements.

Derived values

Computed from source-backed inputs via standard formulae — not observations. Every input and constant is traced below.

Bulk density4.95 g/cm³derived
Formula & inputs
Formula: ρ = M / (4⁄3·π·r³) (v1.0.0, impl v1.0.0)
Inputs:
- massEarth = 1.04 M⊕ · NASA
- radiusEarth = 1.05 R⊕ · NASA
Assumptions: M⊕ = 5.972e+24 kg, R⊕ = 6371000 m (IAU 2015 B3 nominal); Assumes a uniform sphere.
Limitations: Withheld above 30 g/cm³ (inconsistent mass/radius inputs).; Archive mass/radius carry no propagated uncertainty here.
Uncertainty: not propagated (inputs carry no catalogued uncertainty)
Computed as of 2026-06-29.

Scientific citations

Real, source-backed references — primary papers first, then datasets and institutional sources. Formatted through the citation engine; nothing is fabricated.

Peer-reviewed paperSeven temperate terrestrial planets around the nearby ultracool dwarf star TRAPPIST-1

Michaël Gillon & et al. · Nature 542, 456–460 · 2017

Nature · doi:10.1038/nature21360

Cite (APA / BibTeX)

Michaël Gillon & et al. (2017). Seven temperate terrestrial planets around the nearby ultracool dwarf star TRAPPIST-1. Nature 542, 456–460. Nature. https://doi.org/10.1038/nature21360

@misc{cite:gillon-2017-trappist,
  title        = {Seven temperate terrestrial planets around the nearby ultracool dwarf star TRAPPIST-1},
  author       = {Michaël Gillon and et al.},
  organization = {Nature},
  howpublished = {Nature 542, 456–460},
  year         = {2017},
  doi          = {10.1038/nature21360},
  url          = {https://doi.org/10.1038/nature21360},
  note         = {The seven Earth-sized TRAPPIST-1 planets.}
}

Archive pageTRAPPIST-1 f — NASA Exoplanet Archive

NASA Exoplanet Science Institute (Caltech/IPAC)

Cite (APA / BibTeX)

NASA Exoplanet Science Institute (Caltech/IPAC) (n.d.). TRAPPIST-1 f — NASA Exoplanet Archive. NASA Exoplanet Science Institute (Caltech/IPAC). https://exoplanetarchive.ipac.caltech.edu/

@misc{cite:exoarchive-exoplanet-trappist-1-f,
  title        = {TRAPPIST-1 f — NASA Exoplanet Archive},
  organization = {NASA Exoplanet Science Institute (Caltech/IPAC)},
  year         = {n.d.},
  url          = {https://exoplanetarchive.ipac.caltech.edu/},
  note         = {Confirmed parameters and discovery references for TRAPPIST-1 f.}
}

Quality & authority

Substantial

Unreviewed

Description: Complete
Source coverage: Complete
Relationship coverage: Complete
Review coverage: None
Citation coverage: None
Image coverage: Not applicable

Data from the NASA Exoplanet Archive. See source quality.