HD 211970 b
Astrophysical Synthesis & Habitability Characterization
HD 211970 b is a confirmed sub-neptune exoplanet orbiting the star HD 211970, located approximately 42.8 light-years (13.13 parsecs) from the Solar System. First announced in 2019 by Las Campanas Observatory using the Radial Velocity detection technique (measuring periodic Doppler reflex motion in the host star's spectrum), this world measures 3.66 Earth radii (0.33 Jupiter radii) and has a measured mass of 13 Earth masses. Combining its mass and radius yields a mean bulk density of 1.46 g/cm³ (a low bulk density dominated by an extended hydrogen-helium gaseous envelope), a surface gravity of 0.97 g⊕ (9.51 m/s²), and an escape velocity of 21.1 km/s.
In its orbital architecture around HD 211970, HD 211970 b completes one full revolution every 25.201 Earth days at a semi-major axis of 0.143 AU (orbiting interior to Mercury's 0.387 AU benchmark in the Solar System). Its mean orbital velocity is approximately 61.7 km/s (compared to Earth's 29.8 km/s). Its moderate orbital eccentricity of e = 0.15 carries the world between 0.1215 AU at periapsis and 0.1644 AU at apoapsis, driving measurable seasonal insolation cycles.
⚠️ Thermal Regime (Irradiated / Hot Zone): At an equilibrium temperature of 399 K (+126°C / +259°F) and receiving 4.21 S⊕ (~5,733 W/m²), HD 211970 b orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star HD 211970 is classified as an orange K-type star of spectral type K7 V with an effective photospheric temperature of 4,127 K, a radius of 0.5742 R☉, a mass of 0.61 M☉, an estimated bolometric luminosity of 0.086 L☉. From Earth, HD 211970 shines at apparent V-band magnitude 10.24 (faint and requiring research-grade or CCD telescopic photometry) in the Southern celestial hemisphere.
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: Las Campanas Observatory · Catalogue Source: NASA Exoplanet Archive (IPAC / Caltech).
☀️ Host Star Telemetry
| Host Star Name | HD 211970 |
| Spectral Type | K7 V |
| Effective Temp (Teff) | 4,127 K |
| Stellar Radius | 0.5742 R☉ |
| Stellar Mass | 0.6100 M☉ |
| Bolometric Luminosity | 0.086 L☉ |
| Metallicity [Fe/H] | — |
| Stellar Age | — |
| Apparent Magnitude | V: 10.240 · G: 8.404 |
| System Architecture | 1 Star, 1 Planet |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.143000 AU |
| Orbital Period | 25.201 days |
| Mean Orbital Velocity | 61.7 km/s |
| Orbital Eccentricity (e) | 0.15000 |
| Orbital Inclination (i) | — |
| Mean Bulk Density | 1.46 g/cm³ (21.1 km/s vesc) |
| Insolation Flux | 4.2125 S⊕ (~5,733 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 42.800 LY (13.128 pc) |