HD 213885 b
Astrophysical Synthesis & Habitability Characterization
HD 213885 b is a confirmed super-earth exoplanet orbiting the star HD 213885, located approximately 156.8 light-years (48.09 parsecs) from the Solar System. First announced in 2019 by Transiting Exoplanet Survey Satellite (TESS) using the Transit detection technique (producing an estimated primary transit depth of 0.0211% across the stellar disk), this world measures 1.745 Earth radii and has a measured mass of 8.83 Earth masses. Combining its mass and radius yields a mean bulk density of 9.16 g/cm³ (an iron-enriched, high-compression rocky core), a surface gravity of 2.9 g⊕ (28.44 m/s²), and an escape velocity of 25.2 km/s.
In its orbital architecture around HD 213885, HD 213885 b completes one full revolution every 1.008 Earth days at a semi-major axis of 0.02012 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 217.1 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.
⚠️ Thermal Regime (Irradiated / Hot Zone): At an equilibrium temperature of 2128 K (+1855°C / +3371°F) and receiving 1,882.94 S⊕ (~2,562,681 W/m²), HD 213885 b orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star HD 213885 is classified as a solar-type yellow star of spectral type G with an effective photospheric temperature of 5,978 K, a radius of 1.1011 R☉, a mass of 1.068 M☉, an estimated bolometric luminosity of 1.389 L☉. Stellar evolution modeling indicates an estimated stellar age of 3.8 Gyr and a metallicity of [Fe/H] = -0.04 dex (near-solar heavy-element abundance). From Earth, HD 213885 shines at apparent V-band magnitude 7.95 (accessible to binoculars and small amateur telescopes) in the Southern celestial hemisphere. The HD 213885 system is a multi-planet architecture hosting 2 confirmed worlds, with HD 213885 b sharing its stellar neighborhood alongside HD 213885 c.
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: Transiting Exoplanet Survey Satellite (TESS) · Catalogue Source: NASA Exoplanet Archive (IPAC / Caltech).
☀️ Host Star Telemetry
| Host Star Name | HD 213885 |
| Spectral Type | G |
| Effective Temp (Teff) | 5,978 K |
| Stellar Radius | 1.1011 R☉ |
| Stellar Mass | 1.0680 M☉ |
| Bolometric Luminosity | 1.389 L☉ |
| Metallicity [Fe/H] | -0.040 dex |
| Stellar Age | 3.800 Gyr |
| Apparent Magnitude | V: 7.950 · G: 7.802 |
| System Architecture | 1 Star, 2 Planets |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.020120 AU |
| Orbital Period | 1.008 days |
| Mean Orbital Velocity | 217.1 km/s |
| Orbital Eccentricity (e) | 0.00000 |
| Orbital Inclination (i) | 80.0900° |
| Mean Bulk Density | 9.16 g/cm³ (25.2 km/s vesc) |
| Insolation Flux | 1882.9400 S⊕ (~2,562,681 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 156.800 LY (48.088 pc) |