Kepler-291 b
Astrophysical Synthesis & Habitability Characterization
Kepler-291 b is a confirmed sub-neptune exoplanet orbiting the star Kepler-291, located approximately 5826.7 light-years (1786.48 parsecs) from the Solar System. First announced in 2014 by Kepler using the Transit detection technique (producing an estimated primary transit depth of 0.038% across the stellar disk), this world measures 2.16 Earth radii and has a measured mass of 5.31 Earth masses. Combining its mass and radius yields a mean bulk density of 2.91 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-291, Kepler-291 b completes one full revolution every 3.547 Earth days at a semi-major axis of 0.047 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 144.2 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 1212 K (+939°C / +1722°F) and receiving 627.37 S⊕ (~853,856 W/m²), Kepler-291 b orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star Kepler-291 is classified as a stellar host with an effective photospheric temperature of 6,002 K, a radius of 1.016 R☉, a mass of 1.023 M☉, an estimated bolometric luminosity of 1.202 L☉. Stellar evolution modeling indicates an estimated stellar age of 7.76 Gyr and a metallicity of [Fe/H] = 0.23 dex (metal-rich relative to the Sun). From Earth, Kepler-291 shines at apparent V-band magnitude 16.218 (faint and requiring research-grade or CCD telescopic photometry) in the Northern celestial hemisphere. The Kepler-291 system is a multi-planet architecture hosting 2 confirmed worlds, with Kepler-291 b sharing its stellar neighborhood alongside Kepler-291 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-291 |
| Spectral Type | Unclassified |
| Effective Temp (Teff) | 6,002 K |
| Stellar Radius | 1.0160 R☉ |
| Stellar Mass | 1.0230 M☉ |
| Bolometric Luminosity | 1.202 L☉ |
| Metallicity [Fe/H] | 0.230 dex |
| Stellar Age | 7.760 Gyr |
| Apparent Magnitude | V: 16.218 · G: 15.899 |
| System Architecture | 1 Star, 2 Planets |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.047000 AU |
| Orbital Period | 3.547 days |
| Mean Orbital Velocity | 144.2 km/s |
| Orbital Eccentricity (e) | 0.00000 |
| Orbital Inclination (i) | 86.2000° |
| Mean Bulk Density | 2.91 g/cm³ (17.5 km/s vesc) |
| Insolation Flux | 627.3740 S⊕ (~853,856 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 5826.700 LY (1786.480 pc) |