Key parameters at a glance

A radius of 0.76 Earth radii
A mass of 0.33 Earth masses
Surface gravity around 0.57 g
An orbital period of 18.773 days
Semi-major axis 0.0619 AU
Equilibrium temperature 172 K (-101 °C)
Distance from Earth 40.54 light-years
Earth Similarity Index 0.601
Travel time at Voyager 1 speed 714,938 years
Almost certainly tidally locked to its host star given the close orbit

Context from the literature

TRAPPIST-1h is an exoplanet orbiting around the ultra-cool dwarf star TRAPPIST-1, located 40.7 light-years away from Earth in the constellation Aquarius. It was one of four new exoplanets to be discovered orbiting the star in 2017 using observations from the Spitzer Space Telescope. In the following years, more studies were able to refine its physical parameters.

Excerpted from Wikipedia · full article

6 siblings around TRAPPIST-1

TRAPPIST-1 h shares its host star with 6 other confirmed planets. Side-by-side measurements below.

Planet	Type	Radius (R⊕)	Mass (M⊕)	Period (d)	Eq. T (K)	Year
TRAPPIST-1 b	Rocky Terrestrial	1.12	1.37	1.511	398	2016
TRAPPIST-1 c	Rocky Terrestrial	1.10	1.31	2.422	340	2016
TRAPPIST-1 d	Rocky Terrestrial	0.79	0.39	4.049	286	2016
TRAPPIST-1 e	Rocky Terrestrial	0.92	0.69	6.101	250	2017
TRAPPIST-1 f	Rocky Terrestrial	1.05	1.04	9.208	218	2017
TRAPPIST-1 g	Rocky Terrestrial	1.13	1.32	12.352	197	2017
TRAPPIST-1 h this	Rocky Terrestrial	0.76	0.33	18.773	172	2017

TRAPPIST-1 h Planet Profile

Physical Specs

Radius

0.76 R⊕

Radius (Jupiter)

0.067 R♃

Mass

0.33 M⊕

Mass (Jupiter)

0.001 M♃

Density

4.16 g/cm³

Surface Gravity

0.57 g (Earth)

Classification

Planet Type

Rocky Terrestrial

ESI Score 0.601

HZ Position Outer

Controversial No

Discovery

Year 2017

Method Transit

Facility Multiple Observatories

Telescope Multiple Telescopes

Size rank in cohort

Rank by radius

#505of 570

top 88.4%

This planet

0.76R⊕

Rocky Terrestrial median

1.01R⊕

Nearest-size peers

Kepler-37 c 0.76 R⊕ Kepler-1864 b 0.75 R⊕ K2-413 b 0.76 R⊕

Metric	Earth	TRAPPIST-1 h	Jupiter
Radius (R⊕)	1.00	0.76	11.21
Mass (M⊕)	1.00	0.33	317.83
Density (g/cm³)	5.51	4.16	1.33
Surface Gravity (g)	1.00	0.57	2.53
Insolation (S⊕)	1.00	0.14	0.037

Alternative Mass Estimates

Method	Value	Interpretation
Best measured mass	0.326 M⊕	Direct mass measurement (not derived).

Star Catalogue Identifiers

TIC

TIC 278892590

Gaia DR2

Gaia DR2 2635476908753563008

Gaia DR3

Gaia DR3 2635476908753563008

System

TRAPPIST-1

Percentile among Rocky Terrestrial cohort

Radius 0.755 R⊕ · percentile 11 / cohort 570

Mass 0.326 M⊕ · percentile 8 / cohort 570

Orbital period 18.77 d · percentile 91 / cohort 567

Distance 12.43 pc · percentile 6 / cohort 566

ESI 0.601 · percentile 78 / cohort 570

Orbit & Habitability

Orbital Dynamics

Period

18.773 days

Semi-major axis

0.0619 AU

Eccentricity

0.006

Inclination

89.81 °

Year Length

A year here lasts approximately 18.77 Earth days (5.1% of a terrestrial year) on a nearly circular orbit at a mean orbital distance of 0.0619 AU.

Transit Fingerprint

Depth

0.338 %

Duration

1.269 h

Impact parameter b

0.378

Rp / R★

0.058090

Transit midpoint (BJD)

2,457,662.5741

Photometric dip

Transit produces a flux drop of 3,375 ppm lasting ≈ 1.27 h.

Extended Orbital Architecture

Planet / star radius ratio

0.058090

Semi-major axis / stellar radius

111.817

Impact parameter (b)

0.378

Transit mid-time (BJD)

2,457,662.5741

Long. of periastron (ω)

338.92°

Angular separation (arcsec)

4.98000

Eq. Temperature

172K

(-101 °C)

Insolation (S⊕)

0.14

Earth = 1.00

Earth Similarity (ESI)

0.601

0 = alien, 1 = Earth-identical

Beyond the outer HZ boundary (too cold) — surface water would be frozen. Close-orbiting tidally-locked around a cool host.

Detection Signatures

Transit photometry

A transit dip has been observed from at least one telescope.

Transit timing variations

Gravitational interactions from neighbours have been detected.

Discovery Paper

Primary reference

Gillon et al. 2016

Instrument

Multiple Instruments

Publication

2016-05

Observation locale

Multiple Locales

Discovery cohort

Planets confirmed in 2017 at Multiple Observatories (12 shown).

GJ 625 b · Super-Earth TRAPPIST-1 e · Rocky Terrestrial TRAPPIST-1 f · Rocky Terrestrial TRAPPIST-1 g · Rocky Terrestrial HD 34445 e · Neptune-like BD+03 2562 b · Gas Giant HD 111591 b · Gas Giant HD 34445 d · Neptune-like MOA-2012-BLG-006L b · Gas Giant HD 76920 b · Gas Giant HD 34445 f · Neptune-like HD 40956 b · Gas Giant

Host System: TRAPPIST-1

Spectral Class

M-type red dwarf

Effective Temperature

2,566 K — cooler than the Sun (5,778 K)

Estimated Age

7.60 Gyr — older than the Sun (4.6 Gyr)

Stellar Radius

0.119 R☉

Stellar Mass

0.090 M☉

Metallicity [Fe/H]

0.05

Extended Stellar Properties

Surface gravity (log g)

5.240 dex

Stellar density

75.050 g/cm³

Rotational v·sin i

2.04 km/s

Rotation period

1.40 days

Metallicity ratio

[Fe/H]

Distance

12.43 parsec

Light-years 40.54 ly

V-band magnitude

17.02 mag

Voyager-speed travel 714,938 yr

Multi-band Host Photometry — 13 bands

Astrometric Data

Parallax

80.451 mas

Total Proper Motion

1,026.579 mas/yr

PM Right Ascension

901.00 mas/yr

PM Declination

-492.00 mas/yr

Galactic Cartesian (pc)

x = 0.969 · y = -0.230 · z = -0.088

Equatorial (J2000)

RA 346.62639° · Dec -5.04346°

Galactic ℓ, b

69.715° · -56.649°

Ecliptic λ, β

345.733° · 0.630°

HTM-20 index

915425164

Wikipedia → Image: Wikimedia Commons · NASA/JPL-Caltech · Public domain