HD 207897 b
Astrophysical Synthesis & Habitability Characterization
HD 207897 b is a confirmed sub-neptune exoplanet orbiting the star HD 207897, located approximately 92.3 light-years (28.29 parsecs) from the Solar System. First announced in 2021 by Transiting Exoplanet Survey Satellite (TESS) using the Transit detection technique (producing an estimated primary transit depth of 0.0753% across the stellar disk), this world measures 2.343 Earth radii and has a measured mass of 14.8 Earth masses. Combining its mass and radius yields a mean bulk density of 6.34 g/cm³ (a terrestrial silicate-iron composition comparable to Earth (5.51 g/cm³)), a surface gravity of 2.7 g⊕ (26.48 m/s²), and an escape velocity of 28.1 km/s.
In its orbital architecture around HD 207897, HD 207897 b completes one full revolution every 16.202 Earth days at a semi-major axis of 0.117 AU (orbiting interior to Mercury's 0.387 AU benchmark in the Solar System). Its mean orbital velocity is approximately 78.6 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 582 K (+309°C / +588°F) and receiving 26.50 S⊕ (~36,067 W/m²), HD 207897 b orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star HD 207897 is classified as an orange K-type star of spectral type K0 V with an effective photospheric temperature of 5,106 K, a radius of 0.7827 R☉, a mass of 0.8208 M☉, an estimated bolometric luminosity of 0.374 L☉. Stellar evolution modeling indicates an estimated stellar age of 4.7 Gyr and a metallicity of [Fe/H] = -0.03 dex (near-solar heavy-element abundance). From Earth, HD 207897 shines at apparent V-band magnitude 8.37 (accessible to binoculars and small amateur telescopes) in the Northern 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: Transiting Exoplanet Survey Satellite (TESS) · Catalogue Source: NASA Exoplanet Archive (IPAC / Caltech).
☀️ Host Star Telemetry
| Host Star Name | HD 207897 |
| Spectral Type | K0 V |
| Effective Temp (Teff) | 5,106 K |
| Stellar Radius | 0.7827 R☉ |
| Stellar Mass | 0.8208 M☉ |
| Bolometric Luminosity | 0.374 L☉ |
| Metallicity [Fe/H] | -0.030 dex |
| Stellar Age | 4.700 Gyr |
| Apparent Magnitude | V: 8.370 · G: 8.130 |
| System Architecture | 1 Star, 1 Planet |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.117000 AU |
| Orbital Period | 16.202 days |
| Mean Orbital Velocity | 78.6 km/s |
| Orbital Eccentricity (e) | 0.00000 |
| Orbital Inclination (i) | 88.7570° |
| Mean Bulk Density | 6.34 g/cm³ (28.1 km/s vesc) |
| Insolation Flux | 26.5000 S⊕ (~36,067 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 92.300 LY (28.294 pc) |