Kepler-61 b
Astrophysical Synthesis & Habitability Characterization
Kepler-61 b is a confirmed sub-neptune exoplanet orbiting the star Kepler-61, located approximately 1092.9 light-years (335.08 parsecs) from the Solar System. First announced in 2013 by Kepler using the Transit detection technique (producing an estimated primary transit depth of 0.1011% across the stellar disk), this world measures 2.15 Earth radii and has a measured mass of 5.27 Earth masses. Combining its mass and radius yields a mean bulk density of 2.92 g/cm³ (an intermediate density indicative of a deep water-ice mantle or dense volatile envelope), a surface gravity of 1.14 g⊕ (11.18 m/s²), and an escape velocity of 17.5 km/s.
In its orbital architecture around Kepler-61, Kepler-61 b completes one full revolution every 59.878 Earth days at a semi-major axis of 0.24861 AU (orbiting interior to Mercury's 0.387 AU benchmark in the Solar System). Its mean orbital velocity is approximately 45.2 km/s (compared to Earth's 29.8 km/s). The planet follows a highly eccentric trajectory (e = 0.25, swinging from 0.1865 AU at periapsis out to 0.3108 AU at apoapsis), pointing to past dynamical scattering or secular gravitational perturbations.
✓ Classified as a Temperate Habitable Zone Candidate.
With an estimated equilibrium temperature of 273 K (0°C / +32°F) and an incident stellar irradiance of 1.69 S⊕ (~2,300 W/m²), Kepler-61 b orbits within the empirical circumstellar habitable zone where a rocky surface under sufficient atmospheric pressure can maintain liquid surface water.
The host star Kepler-61 is classified as an orange K-type star of spectral type K7 V with an effective photospheric temperature of 4,017 K, a radius of 0.62 R☉, a mass of 0.635 M☉, an estimated bolometric luminosity of 0.09 L☉. Stellar evolution modeling indicates an estimated stellar age of 1 Gyr and a metallicity of [Fe/H] = 0.03 dex (near-solar heavy-element abundance). From Earth, Kepler-61 shines at apparent V-band magnitude 15.277 (faint and requiring research-grade or CCD telescopic photometry) in the Northern celestial hemisphere.
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-61 |
| Spectral Type | K7 V |
| Effective Temp (Teff) | 4,017 K |
| Stellar Radius | 0.6200 R☉ |
| Stellar Mass | 0.6350 M☉ |
| Bolometric Luminosity | 0.09 L☉ |
| Metallicity [Fe/H] | 0.030 dex |
| Stellar Age | 1.000 Gyr |
| Apparent Magnitude | V: 15.277 · G: 15.043 |
| System Architecture | 1 Star, 1 Planet |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.248610 AU |
| Orbital Period | 59.878 days |
| Mean Orbital Velocity | 45.2 km/s |
| Orbital Eccentricity (e) | 0.25000 |
| Orbital Inclination (i) | 89.8000° |
| Mean Bulk Density | 2.92 g/cm³ (17.5 km/s vesc) |
| Insolation Flux | 1.6900 S⊕ (~2,300 W/m²) |
| Habitable Zone Status | ★ Temperate Zone |
| Celestial Distance | 1092.900 LY (335.079 pc) |