Kepler-1708 b
Astrophysical Synthesis & Habitability Characterization
Kepler-1708 b is a confirmed gas giant exoplanet orbiting the star Kepler-1708, located approximately 5436 light-years (1666.69 parsecs) from the Solar System. First announced in 2021 by Kepler using the Transit detection technique (producing an estimated primary transit depth of 0.6683% across the stellar disk), this world measures 9.96 Earth radii (0.89 Jupiter radii) and has a measured mass of 1462.011 Earth masses (4.6 Jupiter masses). Combining its mass and radius yields a mean bulk density of 8.16 g/cm³ (an iron-enriched, high-compression rocky core), a surface gravity of 14.74 g⊕ (144.55 m/s²), and an escape velocity of 135.5 km/s.
In its orbital architecture around Kepler-1708, Kepler-1708 b completes one full revolution every 737.113 Earth days (2.02Julian years) at a semi-major axis of 1.64 AU (corresponding to the middle-system regime between Mars at 1.52 AU and Jupiter at 5.20 AU). Its mean orbital velocity is approximately 24.2 km/s (compared to Earth's 29.8 km/s). The planet follows a highly eccentric trajectory (e = 0.4, swinging from 0.984 AU at periapsis out to 2.296 AU at apoapsis), pointing to past dynamical scattering or secular gravitational perturbations.
☁️ Atmospheric Regime (Volatile / Gas Envelope): With a radius of 9.960 R⊕, Kepler-1708 b exceeds the empirical ~1.8–2.2 R⊕ Fulton radius valley threshold, indicating a substantial hydrogen-helium or supercritical volatile envelope without a conventional solid terrestrial surface.
The host star Kepler-1708 is classified as a stellar host with an effective photospheric temperature of 6,157 K, a radius of 1.117 R☉, a mass of 1.088 M☉, an estimated bolometric luminosity of 1.609 L☉. Stellar evolution modeling indicates an estimated stellar age of 3.16 Gyr and a metallicity of [Fe/H] = 0 dex (near-solar heavy-element abundance). From Earth, Kepler-1708 shines at apparent V-band magnitude 15.823 (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-1708 |
| Spectral Type | Unclassified |
| Effective Temp (Teff) | 6,157 K |
| Stellar Radius | 1.1170 R☉ |
| Stellar Mass | 1.0880 M☉ |
| Bolometric Luminosity | 1.609 L☉ |
| Metallicity [Fe/H] | 0.000 dex |
| Stellar Age | 3.160 Gyr |
| Apparent Magnitude | V: 15.823 · G: 15.684 |
| System Architecture | 1 Star, 1 Planet |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 1.640000 AU |
| Orbital Period | 737.113 days |
| Mean Orbital Velocity | 24.2 km/s |
| Orbital Eccentricity (e) | 0.40000 |
| Orbital Inclination (i) | — |
| Mean Bulk Density | 8.16 g/cm³ (135.5 km/s vesc) |
| Insolation Flux | 0.5610 S⊕ (~764 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 5436.000 LY (1666.690 pc) |