HD 89345 b
Astrophysical Synthesis & Habitability Characterization
HD 89345 b is a confirmed gas giant exoplanet orbiting the star HD 89345, located approximately 431.7 light-years (132.35 parsecs) from the Solar System. First announced in 2018 by K2 using the Transit detection technique (producing an estimated primary transit depth of 0.1507% across the stellar disk), this world measures 7.398 Earth radii (0.66 Jupiter radii) and has a measured mass of 34.961 Earth masses (0.11 Jupiter masses). Combining its mass and radius yields a mean bulk density of 0.48 g/cm³ (a low bulk density dominated by an extended hydrogen-helium gaseous envelope), a surface gravity of 0.64 g⊕ (6.28 m/s²), and an escape velocity of 24.3 km/s.
In its orbital architecture around HD 89345, HD 89345 b completes one full revolution every 11.814 Earth days at a semi-major axis of 0.1066 AU (orbiting interior to Mercury's 0.387 AU benchmark in the Solar System). Its mean orbital velocity is approximately 98.2 km/s (compared to Earth's 29.8 km/s). Its moderate orbital eccentricity of e = 0.22 carries the world between 0.0831 AU at periapsis and 0.1301 AU at apoapsis, driving measurable seasonal insolation cycles.
⚠️ Thermal Regime (Irradiated / Hot Zone): At an equilibrium temperature of 1089 K (+816°C / +1501°F) and receiving 275.64 S⊕ (~375,150 W/m²), HD 89345 b orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star HD 89345 is classified as a solar-type yellow star of spectral type G5 with an effective photospheric temperature of 5,576 K, a radius of 1.747 R☉, a mass of 1.157 M☉, an estimated bolometric luminosity of 2.647 L☉. Stellar evolution modeling indicates an estimated stellar age of 7.53 Gyr and a metallicity of [Fe/H] = 0.421 dex (metal-rich relative to the Sun). From Earth, HD 89345 shines at apparent V-band magnitude 9.38 (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: K2 · Catalogue Source: NASA Exoplanet Archive (IPAC / Caltech).
☀️ Host Star Telemetry
| Host Star Name | HD 89345 |
| Spectral Type | G5 |
| Effective Temp (Teff) | 5,576 K |
| Stellar Radius | 1.7470 R☉ |
| Stellar Mass | 1.1570 M☉ |
| Bolometric Luminosity | 2.647 L☉ |
| Metallicity [Fe/H] | 0.421 dex |
| Stellar Age | 7.530 Gyr |
| Apparent Magnitude | V: 9.380 · G: 9.217 |
| System Architecture | 1 Star, 1 Planet |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.106600 AU |
| Orbital Period | 11.814 days |
| Mean Orbital Velocity | 98.2 km/s |
| Orbital Eccentricity (e) | 0.22000 |
| Orbital Inclination (i) | 87.2100° |
| Mean Bulk Density | 0.48 g/cm³ (24.3 km/s vesc) |
| Insolation Flux | 275.6427 S⊕ (~375,150 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 431.700 LY (132.345 pc) |