Kepler-445 d
Astrophysical Synthesis & Habitability Characterization
Kepler-445 d is a confirmed terrestrial exoplanet orbiting the star Kepler-445, located approximately 414.9 light-years (127.2 parsecs) from the Solar System. First announced in 2015 by Kepler using the Transit detection technique (producing an estimated primary transit depth of 0.2978% across the stellar disk), this world measures 1.25 Earth radii and has a measured mass of 2.1 Earth masses. Combining its mass and radius yields a mean bulk density of 5.93 g/cm³ (a terrestrial silicate-iron composition comparable to Earth (5.51 g/cm³)), a surface gravity of 1.34 g⊕ (13.14 m/s²), and an escape velocity of 14.5 km/s.
In its orbital architecture around Kepler-445, Kepler-445 d completes one full revolution every 8.153 Earth days at a semi-major axis of 0.0439 AU (an ultra-close orbit less than one-seventh of Mercury's 0.387 AU distance from the Sun, where strong stellar tidal forces typically induce synchronous rotation). Its mean orbital velocity is approximately 58.6 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 305 K (+32°C / +90°F) and an incident stellar irradiance of 4.31 S⊕ (~5,871 W/m²), Kepler-445 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-445 is classified as a low-mass red dwarf of spectral type M4 with an effective photospheric temperature of 3,157 K, a radius of 0.21 R☉, a mass of 0.18 M☉, an estimated bolometric luminosity of 0.00393 L☉. Stellar evolution modeling indicates an estimated stellar age of 6.61 Gyr and a metallicity of [Fe/H] = 0.27 dex (metal-rich relative to the Sun). From Earth, Kepler-445 shines at apparent V-band magnitude 18.19 (faint and requiring research-grade or CCD telescopic photometry) in the Northern celestial hemisphere. The Kepler-445 system is a multi-planet architecture hosting 3 confirmed worlds, with Kepler-445 d sharing its stellar neighborhood alongside Kepler-445 b, Kepler-445 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-445 |
| Spectral Type | M4 |
| Effective Temp (Teff) | 3,157 K |
| Stellar Radius | 0.2100 R☉ |
| Stellar Mass | 0.1800 M☉ |
| Bolometric Luminosity | 0.00393 L☉ |
| Metallicity [Fe/H] | 0.270 dex |
| Stellar Age | 6.610 Gyr |
| Apparent Magnitude | V: 18.190 · G: 16.716 |
| System Architecture | 1 Star, 3 Planets |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.043900 AU |
| Orbital Period | 8.153 days |
| Mean Orbital Velocity | 58.6 km/s |
| Orbital Eccentricity (e) | 0.00000 |
| Orbital Inclination (i) | 89.6100° |
| Mean Bulk Density | 5.93 g/cm³ (14.5 km/s vesc) |
| Insolation Flux | 4.3140 S⊕ (~5,871 W/m²) |
| Habitable Zone Status | ★ Temperate Zone |
| Celestial Distance | 414.900 LY (127.201 pc) |