GJ 3473 c
Astrophysical Synthesis & Habitability Characterization
GJ 3473 c is a confirmed sub-neptune exoplanet orbiting the star GJ 3473, located approximately 89.3 light-years (27.36 parsecs) from the Solar System. First announced in 2020 by Multiple Observatories using the Radial Velocity detection technique (measuring periodic Doppler reflex motion in the host star's spectrum), this world measures 2.63 Earth radii and has a measured mass of 7.41 Earth masses. Combining its mass and radius yields a mean bulk density of 2.25 g/cm³ (an intermediate density indicative of a deep water-ice mantle or dense volatile envelope), a surface gravity of 1.07 g⊕ (10.49 m/s²), and an escape velocity of 18.8 km/s.
In its orbital architecture around GJ 3473, GJ 3473 c completes one full revolution every 15.509 Earth days at a semi-major axis of 0.0876 AU (orbiting interior to Mercury's 0.387 AU benchmark in the Solar System). Its mean orbital velocity is approximately 61.4 km/s (compared to Earth's 29.8 km/s). The orbit is modeled as circular (e = 0.00), maintaining a constant stellar distance throughout its year.
☁️ Atmospheric Regime (Volatile / Gas Envelope): With a radius of 2.630 R⊕, GJ 3473 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 3473 is classified as a low-mass red dwarf of spectral type M4 with an effective photospheric temperature of 3,347 K, a radius of 0.364 R☉, a mass of 0.36 M☉, an estimated bolometric luminosity of 0.015 L☉. Stellar evolution modeling indicates a metallicity of [Fe/H] = 0.11 dex (metal-rich relative to the Sun). From Earth, GJ 3473 shines at apparent V-band magnitude 13.74 (faint and requiring research-grade or CCD telescopic photometry) in the Northern celestial hemisphere. The GJ 3473 system is a multi-planet architecture hosting 2 confirmed worlds, with GJ 3473 c sharing its stellar neighborhood alongside GJ 3473 b.
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: Multiple Observatories · Catalogue Source: NASA Exoplanet Archive (IPAC / Caltech).
☀️ Host Star Telemetry
| Host Star Name | GJ 3473 |
| Spectral Type | M4 |
| Effective Temp (Teff) | 3,347 K |
| Stellar Radius | 0.3640 R☉ |
| Stellar Mass | 0.3600 M☉ |
| Bolometric Luminosity | 0.015 L☉ |
| Metallicity [Fe/H] | 0.110 dex |
| Stellar Age | — |
| Apparent Magnitude | V: 13.740 · G: 12.465 |
| System Architecture | 2 Stars, 2 Planets |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.087600 AU |
| Orbital Period | 15.509 days |
| Mean Orbital Velocity | 61.4 km/s |
| Orbital Eccentricity (e) | 0.00000 |
| Orbital Inclination (i) | — |
| Mean Bulk Density | 2.25 g/cm³ (18.8 km/s vesc) |
| Insolation Flux | 1.9500 S⊕ (~2,654 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 89.300 LY (27.364 pc) |