Kepler-561 b
Astrophysical Synthesis & Habitability Characterization
Kepler-561 b is a confirmed gas giant exoplanet orbiting the star Kepler-561, located approximately 2026.7 light-years (621.38 parsecs) from the Solar System. First announced in 2016 by Kepler using the Transit detection technique (producing an estimated primary transit depth of 0.4608% across the stellar disk), this world measures 6.96 Earth radii (0.62 Jupiter radii) and has a measured mass of 38.7 Earth masses (0.12 Jupiter masses). Combining its mass and radius yields a mean bulk density of 0.63 g/cm³ (a low bulk density dominated by an extended hydrogen-helium gaseous envelope), a surface gravity of 0.8 g⊕ (7.85 m/s²), and an escape velocity of 26.4 km/s.
In its orbital architecture around Kepler-561, Kepler-561 b completes one full revolution every 58.362 Earth days at a semi-major axis of 0.29256 AU (orbiting interior to Mercury's 0.387 AU benchmark in the Solar System). Its mean orbital velocity is approximately 54.5 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 446 K (+173°C / +343°F) and receiving 7.57 S⊕ (~10,296 W/m²), Kepler-561 b orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star Kepler-561 is classified as a stellar host with an effective photospheric temperature of 5,646 K, a radius of 0.94 R☉, a mass of 0.96 M☉, an estimated bolometric luminosity of 0.806 L☉. Stellar evolution modeling indicates an estimated stellar age of 4.27 Gyr and a metallicity of [Fe/H] = 0.02 dex (near-solar heavy-element abundance). From Earth, Kepler-561 shines at apparent V-band magnitude 14.427 (faint and requiring research-grade or CCD telescopic photometry) in the Northern celestial hemisphere. The Kepler-561 system is a multi-planet architecture hosting 2 confirmed worlds, with Kepler-561 b sharing its stellar neighborhood alongside Kepler-561 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-561 |
| Spectral Type | Unclassified |
| Effective Temp (Teff) | 5,646 K |
| Stellar Radius | 0.9400 R☉ |
| Stellar Mass | 0.9600 M☉ |
| Bolometric Luminosity | 0.806 L☉ |
| Metallicity [Fe/H] | 0.020 dex |
| Stellar Age | 4.270 Gyr |
| Apparent Magnitude | V: 14.427 · G: 14.332 |
| System Architecture | 1 Star, 2 Planets |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.292560 AU |
| Orbital Period | 58.362 days |
| Mean Orbital Velocity | 54.5 km/s |
| Orbital Eccentricity (e) | 0.00000 |
| Orbital Inclination (i) | 89.6700° |
| Mean Bulk Density | 0.63 g/cm³ (26.4 km/s vesc) |
| Insolation Flux | 7.5650 S⊕ (~10,296 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 2026.700 LY (621.378 pc) |