BD+20 2457 c
Astrophysical Synthesis & Habitability Characterization
BD+20 2457 c is a confirmed gas giant exoplanet orbiting the star BD+20 2457, located approximately 5021.9 light-years (1539.71 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 12.4 Earth radii (1.11 Jupiter radii) and has a measured mass of 3963.17 Earth masses (12.47 Jupiter masses). Combining its mass and radius yields a mean bulk density of 11.46 g/cm³ (an iron-enriched, high-compression rocky core), a surface gravity of 25.78 g⊕ (252.82 m/s²), and an escape velocity of 200 km/s.
In its orbital architecture around BD+20 2457, BD+20 2457 c completes one full revolution every 621.99 Earth days (1.7Julian years) at a semi-major axis of 2.01 AU (corresponding to the middle-system regime between Mars at 1.52 AU and Jupiter at 5.20 AU). Its mean orbital velocity is approximately 35.2 km/s (compared to Earth's 29.8 km/s). Its moderate orbital eccentricity of e = 0.18 carries the world between 1.6482 AU at periapsis and 2.3718 AU at apoapsis, driving measurable seasonal insolation cycles.
⚠️ Thermal Regime (Irradiated / Hot Zone): At an equilibrium temperature of 985 K (+712°C / +1314°F) and receiving 366.11 S⊕ (~498,271 W/m²), BD+20 2457 c orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star BD+20 2457 is classified as an orange K-type star of spectral type K2 II with an effective photospheric temperature of 4,137 K, a radius of 49 R☉, a mass of 2.8 M☉, an estimated bolometric luminosity of 630.992 L☉. Stellar evolution modeling indicates a metallicity of [Fe/H] = -1 dex (metal-poor relative to the Sun). From Earth, BD+20 2457 shines at apparent V-band magnitude 9.743 (accessible to binoculars and small amateur telescopes) in the Northern celestial hemisphere. The BD+20 2457 system is a multi-planet architecture hosting 2 confirmed worlds, with BD+20 2457 c sharing its stellar neighborhood alongside BD+20 2457 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: McDonald Observatory · Catalogue Source: NASA Exoplanet Archive (IPAC / Caltech).
☀️ Host Star Telemetry
| Host Star Name | BD+20 2457 |
| Spectral Type | K2 II |
| Effective Temp (Teff) | 4,137 K |
| Stellar Radius | 49.0000 R☉ |
| Stellar Mass | 2.8000 M☉ |
| Bolometric Luminosity | 630.992 L☉ |
| Metallicity [Fe/H] | -1.000 dex |
| Stellar Age | — |
| Apparent Magnitude | V: 9.743 · G: 9.227 |
| System Architecture | 1 Star, 2 Planets |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 2.010000 AU |
| Orbital Period | 621.99 days |
| Mean Orbital Velocity | 35.2 km/s |
| Orbital Eccentricity (e) | 0.18000 |
| Orbital Inclination (i) | — |
| Mean Bulk Density | 11.46 g/cm³ (200 km/s vesc) |
| Insolation Flux | 366.1069 S⊕ (~498,271 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 5021.900 LY (1539.710 pc) |