HD 135694 b
Astrophysical Synthesis & Habitability Characterization
HD 135694 b is a confirmed sub-neptune exoplanet orbiting the star HD 135694, located approximately 240.9 light-years (73.87 parsecs) from the Solar System. First announced in 2023 by Transiting Exoplanet Survey Satellite (TESS) using the Transit detection technique (producing an estimated primary transit depth of 0.0588% across the stellar disk), this world measures 2.857 Earth radii and has a measured mass of 6.1 Earth masses. Combining its mass and radius yields a mean bulk density of 1.44 g/cm³ (a low bulk density dominated by an extended hydrogen-helium gaseous envelope), a surface gravity of 0.75 g⊕ (7.35 m/s²), and an escape velocity of 16.3 km/s.
In its orbital architecture around HD 135694, HD 135694 b completes one full revolution every 15.923 Earth days at a semi-major axis of 0.124695 AU (orbiting interior to Mercury's 0.387 AU benchmark in the Solar System). Its mean orbital velocity is approximately 85.2 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 751 K (+478°C / +892°F) and receiving 71.80 S⊕ (~97,720 W/m²), HD 135694 b orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star HD 135694 is classified as a stellar host with an effective photospheric temperature of 5,712 K, a radius of 1.08 R☉, a mass of 1.02 M☉, an estimated bolometric luminosity of 1.114 L☉. Stellar evolution modeling indicates an estimated stellar age of 9.8 Gyr and a metallicity of [Fe/H] = -0.121 dex (metal-poor relative to the Sun). From Earth, HD 135694 shines at apparent V-band magnitude 9.08 (accessible to binoculars and small amateur telescopes) 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: Transiting Exoplanet Survey Satellite (TESS) · Catalogue Source: NASA Exoplanet Archive (IPAC / Caltech).
☀️ Host Star Telemetry
| Host Star Name | HD 135694 |
| Spectral Type | Unclassified |
| Effective Temp (Teff) | 5,712 K |
| Stellar Radius | 1.0800 R☉ |
| Stellar Mass | 1.0200 M☉ |
| Bolometric Luminosity | 1.114 L☉ |
| Metallicity [Fe/H] | -0.121 dex |
| Stellar Age | 9.800 Gyr |
| Apparent Magnitude | V: 9.080 · G: 8.913 |
| System Architecture | 1 Star, 1 Planet |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.124695 AU |
| Orbital Period | 15.923 days |
| Mean Orbital Velocity | 85.2 km/s |
| Orbital Eccentricity (e) | 0.00000 |
| Orbital Inclination (i) | — |
| Mean Bulk Density | 1.44 g/cm³ (16.3 km/s vesc) |
| Insolation Flux | 71.8000 S⊕ (~97,720 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 240.900 LY (73.871 pc) |