CONFIRMED EXOPLANET · Terrestrial

TRAPPIST-1 b

Orbits Host Star: TRAPPIST-1 (Type M8.0 V) · Distance: 40.500 Light-Years (12.430 pc)

Planetary Radius

1.116 R⊕

Planetary Mass

1.374 M⊕

Surface Gravity

1.1 g / g⊕

Equilibrium Temp

398K (+125°C / +257°F)

Orbital Period

1.511 days

Discovery Year

2016 (Transit)

Earth Similarity (ESI)

                            0.77                            / 1.00
                                                            Moderate
                                                    

Insolation Flux

4.15 S⊕

Astrophysical Synthesis & Habitability Characterization

TRAPPIST-1 b is a confirmed terrestrial exoplanet orbiting the star TRAPPIST-1, located approximately 40.5 light-years (12.43 parsecs) from the Solar System. First announced in 2016 by La Silla Observatory using the Transit detection technique (producing an estimated primary transit depth of 0.7367% across the stellar disk), this world measures 1.116 Earth radii and has a measured mass of 1.374 Earth masses. Combining its mass and radius yields a mean bulk density of 5.45 g/cm³ (a terrestrial silicate-iron composition comparable to Earth (5.51 g/cm³)), a surface gravity of 1.1 g⊕ (10.79 m/s²), and an escape velocity of 12.4 km/s.

In its orbital architecture around TRAPPIST-1, TRAPPIST-1 b completes one full revolution every 1.511 Earth days at a semi-major axis of 0.01154 AU (an ultra-close orbit less than one-seventh of Mercury's 0.387 AU distance from the Sun, where strong stellar tidal forces typically induce synchronous rotation). Its mean orbital velocity is approximately 83.1 km/s (compared to Earth's 29.8 km/s). With a near-circular eccentricity of e = 0.00622 (ranging from 0.0115 AU at periapsis to 0.0116 AU at apoapsis), the planet experiences minimal orbital distance variation.

⚠️ Thermal Regime (Irradiated / Hot Zone): At an equilibrium temperature of 398 K (+125°C / +257°F) and receiving 4.15 S⊕ (~5,652 W/m²), TRAPPIST-1 b orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.

The host star TRAPPIST-1 is classified as a low-mass red dwarf of spectral type M8.0 V with an effective photospheric temperature of 2,566 K, a radius of 0.1192 R☉, a mass of 0.0898 M☉, an estimated bolometric luminosity of 0.00055 L☉. Stellar evolution modeling indicates an estimated stellar age of 7.6 Gyr and a metallicity of [Fe/H] = 0.052 dex (metal-rich relative to the Sun). From Earth, TRAPPIST-1 shines at apparent V-band magnitude 17.02 (faint and requiring research-grade or CCD telescopic photometry) in the Southern celestial hemisphere. The TRAPPIST-1 system is a multi-planet architecture hosting 7 confirmed worlds, with TRAPPIST-1 b sharing its stellar neighborhood alongside TRAPPIST-1 c, TRAPPIST-1 d, TRAPPIST-1 e, TRAPPIST-1 f, TRAPPIST-1 g, TRAPPIST-1 h.

Earth Similarity Index (ESI): 0.77 Earth Baseline = 1.00

0.00 Dissimilar 0.50 Mars Scale 0.70 Analog Regime 1.00 Earth

Methodology: Computed using the Schulze-Makuch et al. (2011) weighted metric comparing physical interior (radius, estimated density) and surface thermal regime (escape velocity, equilibrium temperature).

Discovery Facility: La Silla Observatory · Catalogue Source: NASA Exoplanet Archive (IPAC / Caltech).

☀️ Host Star Telemetry

Host Star Name	TRAPPIST-1
Spectral Type	M8.0 V
Effective Temp (Teff)	2,566 K
Stellar Radius	0.1192 R☉
Stellar Mass	0.0898 M☉
Bolometric Luminosity	0.00055 L☉
Metallicity [Fe/H]	0.052 dex
Stellar Age	7.600 Gyr
Apparent Magnitude	V: 17.020 · G: 15.645
System Architecture	1 Star, 7 Planets

🪐 Orbital & Physical Dynamics

Semi-Major Axis (a)	0.011540 AU
Orbital Period	1.511 days
Mean Orbital Velocity	83.1 km/s
Orbital Eccentricity (e)	0.00622
Orbital Inclination (i)	89.7280°
Mean Bulk Density	5.45 g/cm³ (12.4 km/s v_esc)
Insolation Flux	4.1530 S⊕ (~5,652 W/m²)
Habitable Zone Status	Exterior / Non-HZ
Celestial Distance	40.500 LY (12.430 pc)