Kepler-616 d
Astrophysical Synthesis & Habitability Characterization
Kepler-616 d is a confirmed sub-neptune exoplanet orbiting the star Kepler-616, located approximately 3084.7 light-years (945.78 parsecs) from the Solar System. First announced in 2021 by Kepler using the Transit detection technique (producing an estimated primary transit depth of 0.062% across the stellar disk), this world measures 2.653 Earth radii and has a measured mass of 7.52 Earth masses. Combining its mass and radius yields a mean bulk density of 2.22 g/cm³ (an intermediate density indicative of a deep water-ice mantle or dense volatile envelope), a surface gravity of 1.07 g⊕ (10.49 m/s²), and an escape velocity of 18.8 km/s.
In its orbital architecture around Kepler-616, Kepler-616 d completes one full revolution every 51.067 Earth days at a semi-major axis of 0.2749 AU (orbiting interior to Mercury's 0.387 AU benchmark in the Solar System). 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.
⚠️ Thermal Regime (Irradiated / Hot Zone): At an equilibrium temperature of 499 K (+226°C / +439°F) and receiving 14.69 S⊕ (~19,993 W/m²), Kepler-616 d orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star Kepler-616 is classified as a stellar host with an effective photospheric temperature of 6,004 K, a radius of 0.977 R☉, a mass of 1.061 M☉, an estimated bolometric luminosity of 1.113 L☉. Stellar evolution modeling indicates an estimated stellar age of 0.4 Gyr and a metallicity of [Fe/H] = -0.02 dex (near-solar heavy-element abundance). From Earth, Kepler-616 shines at apparent V-band magnitude 15.021 (faint and requiring research-grade or CCD telescopic photometry) in the Northern celestial hemisphere. The Kepler-616 system is a multi-planet architecture hosting 3 confirmed worlds, with Kepler-616 d sharing its stellar neighborhood alongside Kepler-616 b, Kepler-616 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-616 |
| Spectral Type | Unclassified |
| Effective Temp (Teff) | 6,004 K |
| Stellar Radius | 0.9770 R☉ |
| Stellar Mass | 1.0610 M☉ |
| Bolometric Luminosity | 1.113 L☉ |
| Metallicity [Fe/H] | -0.020 dex |
| Stellar Age | 0.400 Gyr |
| Apparent Magnitude | V: 15.021 · G: 14.948 |
| System Architecture | 1 Star, 3 Planets |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.274900 AU |
| Orbital Period | 51.067 days |
| Mean Orbital Velocity | 58.6 km/s |
| Orbital Eccentricity (e) | 0.00000 |
| Orbital Inclination (i) | 89.6600° |
| Mean Bulk Density | 2.22 g/cm³ (18.8 km/s vesc) |
| Insolation Flux | 14.6900 S⊕ (~19,993 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 3084.700 LY (945.775 pc) |