Kepler-402 d
Astrophysical Synthesis & Habitability Characterization
Kepler-402 d is a confirmed super-earth exoplanet orbiting the star Kepler-402, located approximately 2039.6 light-years (625.34 parsecs) from the Solar System. First announced in 2014 by Kepler using the Transit detection technique (producing an estimated primary transit depth of 0.01% across the stellar disk), this world measures 1.38 Earth radii and has a measured mass of 2.48 Earth masses. Combining its mass and radius yields a mean bulk density of 5.2 g/cm³ (a terrestrial silicate-iron composition comparable to Earth (5.51 g/cm³)), a surface gravity of 1.3 g⊕ (12.75 m/s²), and an escape velocity of 15 km/s.
In its orbital architecture around Kepler-402, Kepler-402 d completes one full revolution every 8.921 Earth days at a semi-major axis of 0.087 AU (orbiting interior to Mercury's 0.387 AU benchmark in the Solar System). Its mean orbital velocity is approximately 106.1 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 1006 K (+733°C / +1351°F) and receiving 214.28 S⊕ (~291,631 W/m²), Kepler-402 d orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star Kepler-402 is classified as a stellar host with an effective photospheric temperature of 6,090 K, a radius of 1.264 R☉, a mass of 1.072 M☉, an estimated bolometric luminosity of 1.972 L☉. Stellar evolution modeling indicates an estimated stellar age of 1.4 Gyr and a metallicity of [Fe/H] = -0.08 dex (near-solar heavy-element abundance). From Earth, Kepler-402 shines at apparent V-band magnitude 13.27 (faint and requiring research-grade or CCD telescopic photometry) in the Northern celestial hemisphere. The Kepler-402 system is a multi-planet architecture hosting 4 confirmed worlds, with Kepler-402 d sharing its stellar neighborhood alongside Kepler-402 b, Kepler-402 c, Kepler-402 e.
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-402 |
| Spectral Type | Unclassified |
| Effective Temp (Teff) | 6,090 K |
| Stellar Radius | 1.2640 R☉ |
| Stellar Mass | 1.0720 M☉ |
| Bolometric Luminosity | 1.972 L☉ |
| Metallicity [Fe/H] | -0.080 dex |
| Stellar Age | 1.400 Gyr |
| Apparent Magnitude | V: 13.270 · G: 13.192 |
| System Architecture | 1 Star, 4 Planets |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.087000 AU |
| Orbital Period | 8.921 days |
| Mean Orbital Velocity | 106.1 km/s |
| Orbital Eccentricity (e) | 0.00000 |
| Orbital Inclination (i) | 89.6000° |
| Mean Bulk Density | 5.2 g/cm³ (15 km/s vesc) |
| Insolation Flux | 214.2770 S⊕ (~291,631 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 2039.600 LY (625.339 pc) |