Kepler-87 c
Astrophysical Synthesis & Habitability Characterization
Kepler-87 c is a confirmed gas giant exoplanet orbiting the star Kepler-87, located approximately 4021.2 light-years (1232.9 parsecs) from the Solar System. First announced in 2013 by Kepler using the Transit detection technique (producing an estimated primary transit depth of 0.0957% across the stellar disk), this world measures 6.14 Earth radii (0.55 Jupiter radii) and has a measured mass of 6.4 Earth masses. Combining its mass and radius yields a mean bulk density of 0.15 g/cm³ (a low bulk density dominated by an extended hydrogen-helium gaseous envelope), a surface gravity of 0.17 g⊕ (1.67 m/s²), and an escape velocity of 11.4 km/s.
In its orbital architecture around Kepler-87, Kepler-87 c completes one full revolution every 191.232 Earth days at a semi-major axis of 0.676 AU (situated at an orbital separation between Mercury's 0.39 AU and Venus's 0.72 AU). Its mean orbital velocity is approximately 38.5 km/s (compared to Earth's 29.8 km/s). With a near-circular eccentricity of e = 0.039 (ranging from 0.6496 AU at periapsis to 0.7024 AU at apoapsis), the planet experiences minimal orbital distance variation.
⚠️ Thermal Regime (Irradiated / Hot Zone): At an equilibrium temperature of 403 K (+130°C / +266°F) and receiving 4.66 S⊕ (~6,337 W/m²), Kepler-87 c orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star Kepler-87 is classified as a stellar host with an effective photospheric temperature of 5,600 K, a radius of 1.82 R☉, a mass of 1.1 M☉, an estimated bolometric luminosity of 2.923 L☉. Stellar evolution modeling indicates an estimated stellar age of 7.5 Gyr and a metallicity of [Fe/H] = -0.17 dex (metal-poor relative to the Sun). From Earth, Kepler-87 shines at apparent V-band magnitude 14.681 (faint and requiring research-grade or CCD telescopic photometry) in the Northern celestial hemisphere. The Kepler-87 system is a multi-planet architecture hosting 2 confirmed worlds, with Kepler-87 c sharing its stellar neighborhood alongside Kepler-87 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: Kepler · Catalogue Source: NASA Exoplanet Archive (IPAC / Caltech).
☀️ Host Star Telemetry
| Host Star Name | Kepler-87 |
| Spectral Type | Unclassified |
| Effective Temp (Teff) | 5,600 K |
| Stellar Radius | 1.8200 R☉ |
| Stellar Mass | 1.1000 M☉ |
| Bolometric Luminosity | 2.923 L☉ |
| Metallicity [Fe/H] | -0.170 dex |
| Stellar Age | 7.500 Gyr |
| Apparent Magnitude | V: 14.681 · G: 14.587 |
| System Architecture | 1 Star, 2 Planets |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.676000 AU |
| Orbital Period | 191.232 days |
| Mean Orbital Velocity | 38.5 km/s |
| Orbital Eccentricity (e) | 0.03900 |
| Orbital Inclination (i) | 89.5880° |
| Mean Bulk Density | 0.15 g/cm³ (11.4 km/s vesc) |
| Insolation Flux | 4.6560 S⊕ (~6,337 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 4021.200 LY (1232.900 pc) |