HD 240210 b
Astrophysical Synthesis & Habitability Characterization
HD 240210 b is a confirmed gas giant exoplanet orbiting the star HD 240210, located approximately 1214.6 light-years (372.41 parsecs) from the Solar System. First announced in 2009 by McDonald Observatory using the Radial Velocity detection technique (measuring periodic Doppler reflex motion in the host star's spectrum), this world measures 12.8 Earth radii (1.14 Jupiter radii) and has a measured mass of 1655.82 Earth masses (5.21 Jupiter masses). Combining its mass and radius yields a mean bulk density of 4.35 g/cm³ (a terrestrial silicate-iron composition comparable to Earth (5.51 g/cm³)), a surface gravity of 10.11 g⊕ (99.15 m/s²), and an escape velocity of 127.2 km/s.
In its orbital architecture around HD 240210, HD 240210 b completes one full revolution every 501.75 Earth days (1.37Julian years) at a semi-major axis of 1.16 AU (comparable to the inner terrestrial zone between Venus, Earth at 1.00 AU, and Mars at 1.52 AU). Its mean orbital velocity is approximately 25.2 km/s (compared to Earth's 29.8 km/s). Its moderate orbital eccentricity of e = 0.15 carries the world between 0.986 AU at periapsis and 1.334 AU at apoapsis, driving measurable seasonal insolation cycles.
⚠️ Thermal Regime (Irradiated / Hot Zone): At an equilibrium temperature of 971 K (+698°C / +1288°F) and receiving 26.37 S⊕ (~35,887 W/m²), HD 240210 b orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star HD 240210 is classified as an orange K-type star of spectral type K3 III with an effective photospheric temperature of 4,297 K, a radius of 25.4568 R☉, a mass of 0.82 M☉, an estimated bolometric luminosity of 198.225 L☉. Stellar evolution modeling indicates an estimated stellar age of 5.085 Gyr and a metallicity of [Fe/H] = -0.18 dex (metal-poor relative to the Sun). From Earth, HD 240210 shines at apparent V-band magnitude 8.27 (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: McDonald Observatory · Catalogue Source: NASA Exoplanet Archive (IPAC / Caltech).
☀️ Host Star Telemetry
| Host Star Name | HD 240210 |
| Spectral Type | K3 III |
| Effective Temp (Teff) | 4,297 K |
| Stellar Radius | 25.4568 R☉ |
| Stellar Mass | 0.8200 M☉ |
| Bolometric Luminosity | 198.225 L☉ |
| Metallicity [Fe/H] | -0.180 dex |
| Stellar Age | 5.085 Gyr |
| Apparent Magnitude | V: 8.270 · G: 7.645 |
| System Architecture | 1 Star, 1 Planet |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 1.160000 AU |
| Orbital Period | 501.75 days |
| Mean Orbital Velocity | 25.2 km/s |
| Orbital Eccentricity (e) | 0.15000 |
| Orbital Inclination (i) | — |
| Mean Bulk Density | 4.35 g/cm³ (127.2 km/s vesc) |
| Insolation Flux | 26.3684 S⊕ (~35,887 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 1214.600 LY (372.405 pc) |