Kepler-174 d
Astrophysical Synthesis & Habitability Characterization
Kepler-174 d is a confirmed sub-neptune exoplanet orbiting the star Kepler-174, located approximately 1254.9 light-years (384.76 parsecs) from the Solar System. First announced in 2014 by Kepler using the Transit detection technique (producing an estimated primary transit depth of 0.1042% across the stellar disk), this world measures 2.19 Earth radii and has a measured mass of 5.43 Earth masses. Combining its mass and radius yields a mean bulk density of 2.85 g/cm³ (an intermediate density indicative of a deep water-ice mantle or dense volatile envelope), a surface gravity of 1.13 g⊕ (11.08 m/s²), and an escape velocity of 17.6 km/s.
In its orbital architecture around Kepler-174, Kepler-174 d completes one full revolution every 247.354 Earth days at a semi-major axis of 0.677 AU (situated at an orbital separation between Mercury's 0.39 AU and Venus's 0.72 AU). Its mean orbital velocity is approximately 29.8 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.
✓ Classified as a Temperate Habitable Zone Candidate.
With an estimated equilibrium temperature of 212 K (-61°C / -78°F) and an incident stellar irradiance of 0.53 S⊕ (~721 W/m²), Kepler-174 d orbits within the empirical circumstellar habitable zone where a rocky surface under sufficient atmospheric pressure can maintain liquid surface water.
The host star Kepler-174 is classified as a stellar host with an effective photospheric temperature of 4,880 K, a radius of 0.622 R☉, a mass of 0.602 M☉, an estimated bolometric luminosity of 0.197 L☉. Stellar evolution modeling indicates an estimated stellar age of 4.9 Gyr and a metallicity of [Fe/H] = -0.56 dex (metal-poor relative to the Sun). From Earth, Kepler-174 shines at apparent V-band magnitude 14.53 (faint and requiring research-grade or CCD telescopic photometry) in the Northern celestial hemisphere. The Kepler-174 system is a multi-planet architecture hosting 3 confirmed worlds, with Kepler-174 d sharing its stellar neighborhood alongside Kepler-174 b, Kepler-174 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-174 |
| Spectral Type | Unclassified |
| Effective Temp (Teff) | 4,880 K |
| Stellar Radius | 0.6220 R☉ |
| Stellar Mass | 0.6020 M☉ |
| Bolometric Luminosity | 0.197 L☉ |
| Metallicity [Fe/H] | -0.560 dex |
| Stellar Age | 4.900 Gyr |
| Apparent Magnitude | V: 14.530 · G: 14.286 |
| System Architecture | 1 Star, 3 Planets |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.677000 AU |
| Orbital Period | 247.354 days |
| Mean Orbital Velocity | 29.8 km/s |
| Orbital Eccentricity (e) | 0.00000 |
| Orbital Inclination (i) | 89.9900° |
| Mean Bulk Density | 2.85 g/cm³ (17.6 km/s vesc) |
| Insolation Flux | 0.5300 S⊕ (~721 W/m²) |
| Habitable Zone Status | ★ Temperate Zone |
| Celestial Distance | 1254.900 LY (384.757 pc) |