Kepler-154 d
Astrophysical Synthesis & Habitability Characterization
Kepler-154 d is a confirmed sub-neptune exoplanet orbiting the star Kepler-154, located approximately 2985 light-years (915.21 parsecs) from the Solar System. First announced in 2016 by Kepler using the Transit detection technique (producing an estimated primary transit depth of 0.129% across the stellar disk), this world measures 3.84 Earth radii (0.34 Jupiter radii) and has a measured mass of 14.1 Earth masses. Combining its mass and radius yields a mean bulk density of 1.37 g/cm³ (a low bulk density dominated by an extended hydrogen-helium gaseous envelope), a surface gravity of 0.96 g⊕ (9.41 m/s²), and an escape velocity of 21.4 km/s.
In its orbital architecture around Kepler-154, Kepler-154 d completes one full revolution every 20.55 Earth days at a semi-major axis of 0.14354 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 657 K (+384°C / +723°F) and receiving 53.00 S⊕ (~72,136 W/m²), Kepler-154 d orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star Kepler-154 is classified as a stellar host with an effective photospheric temperature of 5,769 K, a radius of 0.98 R☉, a mass of 0.98 M☉, an estimated bolometric luminosity of 0.954 L☉. Stellar evolution modeling indicates an estimated stellar age of 4.47 Gyr and a metallicity of [Fe/H] = -0.04 dex (near-solar heavy-element abundance). From Earth, Kepler-154 shines at apparent V-band magnitude 14.646 (faint and requiring research-grade or CCD telescopic photometry) in the Northern celestial hemisphere. The Kepler-154 system is a multi-planet architecture hosting 5 confirmed worlds, with Kepler-154 d sharing its stellar neighborhood alongside Kepler-154 e, Kepler-154 f, Kepler-154 b, Kepler-154 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-154 |
| Spectral Type | Unclassified |
| Effective Temp (Teff) | 5,769 K |
| Stellar Radius | 0.9800 R☉ |
| Stellar Mass | 0.9800 M☉ |
| Bolometric Luminosity | 0.954 L☉ |
| Metallicity [Fe/H] | -0.040 dex |
| Stellar Age | 4.470 Gyr |
| Apparent Magnitude | V: 14.646 · G: 14.512 |
| System Architecture | 1 Star, 5 Planets |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.143540 AU |
| Orbital Period | 20.55 days |
| Mean Orbital Velocity | 76 km/s |
| Orbital Eccentricity (e) | 0.00000 |
| Orbital Inclination (i) | 88.3800° |
| Mean Bulk Density | 1.37 g/cm³ (21.4 km/s vesc) |
| Insolation Flux | 53.0020 S⊕ (~72,136 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 2985.000 LY (915.212 pc) |