Kepler-1729 b
Astrophysical Synthesis & Habitability Characterization
Kepler-1729 b is a confirmed sub-neptune exoplanet orbiting the star Kepler-1729, located approximately 1879.2 light-years (576.18 parsecs) from the Solar System. First announced in 2021 by Kepler using the Transit detection technique (producing an estimated primary transit depth of 0.4768% across the stellar disk), this world measures 3.894 Earth radii (0.35 Jupiter radii) and has a measured mass of 14.4 Earth masses. Combining its mass and radius yields a mean bulk density of 1.34 g/cm³ (a low bulk density dominated by an extended hydrogen-helium gaseous envelope), a surface gravity of 0.95 g⊕ (9.32 m/s²), and an escape velocity of 21.5 km/s.
In its orbital architecture around Kepler-1729, Kepler-1729 b completes one full revolution every 4.221 Earth days at a semi-major axis of 0.0418 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 107.7 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 595 K (+322°C / +612°F) and receiving 29.68 S⊕ (~40,394 W/m²), Kepler-1729 b orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star Kepler-1729 is classified as a stellar host with an effective photospheric temperature of 3,837 K, a radius of 0.517 R☉, a mass of 0.544 M☉, an estimated bolometric luminosity of 0.052 L☉. Stellar evolution modeling indicates an estimated stellar age of 1.2 Gyr and a metallicity of [Fe/H] = -0.06 dex (near-solar heavy-element abundance). From Earth, Kepler-1729 shines at apparent V-band magnitude 15.676 (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-1729 |
| Spectral Type | Unclassified |
| Effective Temp (Teff) | 3,837 K |
| Stellar Radius | 0.5170 R☉ |
| Stellar Mass | 0.5440 M☉ |
| Bolometric Luminosity | 0.052 L☉ |
| Metallicity [Fe/H] | -0.060 dex |
| Stellar Age | 1.200 Gyr |
| Apparent Magnitude | V: 15.676 · G: 15.646 |
| System Architecture | 1 Star, 1 Planet |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.041800 AU |
| Orbital Period | 4.221 days |
| Mean Orbital Velocity | 107.7 km/s |
| Orbital Eccentricity (e) | 0.00000 |
| Orbital Inclination (i) | 85.0300° |
| Mean Bulk Density | 1.34 g/cm³ (21.5 km/s vesc) |
| Insolation Flux | 29.6800 S⊕ (~40,394 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 1879.200 LY (576.181 pc) |