Kepler-27 d
Astrophysical Synthesis & Habitability Characterization
Kepler-27 d is a confirmed sub-neptune exoplanet orbiting the star Kepler-27, located approximately 3406.2 light-years (1044.36 parsecs) from the Solar System. First announced in 2021 by Kepler using the Transit detection technique (producing an estimated primary transit depth of 0.0922% across the stellar disk), this world measures 2.706 Earth radii and has a measured mass of 7.78 Earth masses. Combining its mass and radius yields a mean bulk density of 2.17 g/cm³ (an intermediate density indicative of a deep water-ice mantle or dense volatile envelope), a surface gravity of 1.06 g⊕ (10.4 m/s²), and an escape velocity of 19 km/s.
In its orbital architecture around Kepler-27, Kepler-27 d completes one full revolution every 6.546 Earth days at a semi-major axis of 0.06578 AU (orbiting interior to Mercury's 0.387 AU benchmark in the Solar System). Its mean orbital velocity is approximately 109.3 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 810 K (+537°C / +999°F) and receiving 88.20 S⊕ (~120,040 W/m²), Kepler-27 d orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star Kepler-27 is classified as a stellar host with an effective photospheric temperature of 5,251 K, a radius of 0.817 R☉, a mass of 0.926 M☉, an estimated bolometric luminosity of 0.455 L☉. Stellar evolution modeling indicates an estimated stellar age of 1.62 Gyr and a metallicity of [Fe/H] = 0.21 dex (metal-rich relative to the Sun). From Earth, Kepler-27 shines at apparent V-band magnitude 15.822 (faint and requiring research-grade or CCD telescopic photometry) in the Northern celestial hemisphere. The Kepler-27 system is a multi-planet architecture hosting 3 confirmed worlds, with Kepler-27 d sharing its stellar neighborhood alongside Kepler-27 b, Kepler-27 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: Kepler · Catalogue Source: NASA Exoplanet Archive (IPAC / Caltech).
☀️ Host Star Telemetry
| Host Star Name | Kepler-27 |
| Spectral Type | Unclassified |
| Effective Temp (Teff) | 5,251 K |
| Stellar Radius | 0.8170 R☉ |
| Stellar Mass | 0.9260 M☉ |
| Bolometric Luminosity | 0.455 L☉ |
| Metallicity [Fe/H] | 0.210 dex |
| Stellar Age | 1.620 Gyr |
| Apparent Magnitude | V: 15.822 · G: 15.816 |
| System Architecture | 1 Star, 3 Planets |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.065780 AU |
| Orbital Period | 6.546 days |
| Mean Orbital Velocity | 109.3 km/s |
| Orbital Eccentricity (e) | 0.00000 |
| Orbital Inclination (i) | 87.4600° |
| Mean Bulk Density | 2.17 g/cm³ (19 km/s vesc) |
| Insolation Flux | 88.2000 S⊕ (~120,040 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 3406.200 LY (1044.360 pc) |