GJ 887 c
Astrophysical Synthesis & Habitability Characterization
GJ 887 c is a confirmed sub-neptune exoplanet orbiting the star GJ 887, located approximately 10.7 light-years (3.29 parsecs) from the Solar System. First announced in 2020 by La Silla Observatory using the Radial Velocity detection technique (measuring periodic Doppler reflex motion in the host star's spectrum), this world measures 2.43 Earth radii and has a measured mass of 6.5 Earth masses. Combining its mass and radius yields a mean bulk density of 2.5 g/cm³ (an intermediate density indicative of a deep water-ice mantle or dense volatile envelope), a surface gravity of 1.1 g⊕ (10.79 m/s²), and an escape velocity of 18.3 km/s.
In its orbital architecture around GJ 887, GJ 887 c completes one full revolution every 21.784 Earth days at a semi-major axis of 0.121 AU (orbiting interior to Mercury's 0.387 AU benchmark in the Solar System). Its mean orbital velocity is approximately 60.4 km/s (compared to Earth's 29.8 km/s). Its moderate orbital eccentricity of e = 0.17 carries the world between 0.1004 AU at periapsis and 0.1416 AU at apoapsis, driving measurable seasonal insolation cycles.
☁️ Atmospheric Regime (Volatile / Gas Envelope): With a radius of 2.430 R⊕, GJ 887 c exceeds the empirical ~1.8–2.2 R⊕ Fulton radius valley threshold, indicating a substantial hydrogen-helium or supercritical volatile envelope without a conventional solid terrestrial surface.
The host star GJ 887 is classified as a low-mass red dwarf of spectral type M1 V with an effective photospheric temperature of 3,688 K, a radius of 0.468 R☉, a mass of 0.495 M☉, an estimated bolometric luminosity of 0.036 L☉. Stellar evolution modeling indicates an estimated stellar age of 2.9 Gyr and a metallicity of [Fe/H] = -0.06 dex (near-solar heavy-element abundance). From Earth, GJ 887 shines at apparent V-band magnitude 7.56 (accessible to binoculars and small amateur telescopes) in the Southern celestial hemisphere. The GJ 887 system is a multi-planet architecture hosting 4 confirmed worlds, with GJ 887 c sharing its stellar neighborhood alongside GJ 887 e, GJ 887 b, GJ 887 d.
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 | GJ 887 |
| Spectral Type | M1 V |
| Effective Temp (Teff) | 3,688 K |
| Stellar Radius | 0.4680 R☉ |
| Stellar Mass | 0.4950 M☉ |
| Bolometric Luminosity | 0.036 L☉ |
| Metallicity [Fe/H] | -0.060 dex |
| Stellar Age | 2.900 Gyr |
| Apparent Magnitude | V: 7.560 · G: 6.522 |
| System Architecture | 1 Star, 4 Planets |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.121000 AU |
| Orbital Period | 21.784 days |
| Mean Orbital Velocity | 60.4 km/s |
| Orbital Eccentricity (e) | 0.17000 |
| Orbital Inclination (i) | — |
| Mean Bulk Density | 2.5 g/cm³ (18.3 km/s vesc) |
| Insolation Flux | 2.5000 S⊕ (~3,403 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 10.700 LY (3.287 pc) |