Kepler-244 d
Astrophysical Synthesis & Habitability Characterization
Kepler-244 d is a confirmed sub-neptune exoplanet orbiting the star Kepler-244, located approximately 3380.6 light-years (1036.49 parsecs) from the Solar System. First announced in 2014 by Kepler using the Transit detection technique (producing an estimated primary transit depth of 0.0696% across the stellar disk), this world measures 2.31 Earth radii and has a measured mass of 15.2 Earth masses. Combining its mass and radius yields a mean bulk density of 6.8 g/cm³ (an iron-enriched, high-compression rocky core), a surface gravity of 2.85 g⊕ (27.95 m/s²), and an escape velocity of 28.7 km/s.
In its orbital architecture around Kepler-244, Kepler-244 d completes one full revolution every 20.05 Earth days at a semi-major axis of 0.14 AU (orbiting interior to Mercury's 0.387 AU benchmark in the Solar System). Its mean orbital velocity is approximately 76 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 622 K (+349°C / +660°F) and receiving 31.27 S⊕ (~42,554 W/m²), Kepler-244 d orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star Kepler-244 is classified as a stellar host with an effective photospheric temperature of 5,554 K, a radius of 0.803 R☉, a mass of 0.933 M☉, an estimated bolometric luminosity of 0.55 L☉. Stellar evolution modeling indicates an estimated stellar age of 2.4 Gyr and a metallicity of [Fe/H] = 0.07 dex (metal-rich relative to the Sun). From Earth, Kepler-244 shines at apparent V-band magnitude 15.747 (faint and requiring research-grade or CCD telescopic photometry) in the Northern celestial hemisphere. The Kepler-244 system is a multi-planet architecture hosting 3 confirmed worlds, with Kepler-244 d sharing its stellar neighborhood alongside Kepler-244 b, Kepler-244 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-244 |
| Spectral Type | Unclassified |
| Effective Temp (Teff) | 5,554 K |
| Stellar Radius | 0.8030 R☉ |
| Stellar Mass | 0.9330 M☉ |
| Bolometric Luminosity | 0.55 L☉ |
| Metallicity [Fe/H] | 0.070 dex |
| Stellar Age | 2.400 Gyr |
| Apparent Magnitude | V: 15.747 · G: 15.546 |
| System Architecture | 1 Star, 3 Planets |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.140000 AU |
| Orbital Period | 20.05 days |
| Mean Orbital Velocity | 76 km/s |
| Orbital Eccentricity (e) | 0.00000 |
| Orbital Inclination (i) | 89.3100° |
| Mean Bulk Density | 6.8 g/cm³ (28.7 km/s vesc) |
| Insolation Flux | 31.2670 S⊕ (~42,554 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 3380.600 LY (1036.490 pc) |