HD 1605 c
Astrophysical Synthesis & Habitability Characterization
HD 1605 c is a confirmed gas giant exoplanet orbiting the star HD 1605, located approximately 289.6 light-years (88.81 parsecs) from the Solar System. First announced in 2015 by Multiple Observatories using the Radial Velocity detection technique (measuring periodic Doppler reflex motion in the host star's spectrum), this world measures 13 Earth radii (1.16 Jupiter radii) and has a measured mass of 1150.545 Earth masses (3.62 Jupiter masses). Combining its mass and radius yields a mean bulk density of 2.89 g/cm³ (an intermediate density indicative of a deep water-ice mantle or dense volatile envelope), a surface gravity of 6.81 g⊕ (66.78 m/s²), and an escape velocity of 105.2 km/s.
In its orbital architecture around HD 1605, HD 1605 c completes one full revolution every 2149 Earth days (5.88Julian years) at a semi-major axis of 3.584 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 18.1 km/s (compared to Earth's 29.8 km/s). Its moderate orbital eccentricity of e = 0.099 carries the world between 3.2292 AU at periapsis and 3.9388 AU at apoapsis, driving measurable seasonal insolation cycles.
☁️ Atmospheric Regime (Volatile / Gas Envelope): With a radius of 13.000 R⊕, HD 1605 c 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 HD 1605 is classified as an orange K-type star of spectral type K1 IV with an effective photospheric temperature of 4,915 K, a radius of 3.49 R☉, a mass of 1.33 M☉, an estimated bolometric luminosity of 6.377 L☉. Stellar evolution modeling indicates an estimated stellar age of 4.36 Gyr and a metallicity of [Fe/H] = 0.22 dex (metal-rich relative to the Sun). From Earth, HD 1605 shines at apparent V-band magnitude 7.52 (accessible to binoculars and small amateur telescopes) in the Northern celestial hemisphere. The HD 1605 system is a multi-planet architecture hosting 2 confirmed worlds, with HD 1605 c sharing its stellar neighborhood alongside HD 1605 b.
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: Multiple Observatories · Catalogue Source: NASA Exoplanet Archive (IPAC / Caltech).
☀️ Host Star Telemetry
| Host Star Name | HD 1605 |
| Spectral Type | K1 IV |
| Effective Temp (Teff) | 4,915 K |
| Stellar Radius | 3.4900 R☉ |
| Stellar Mass | 1.3300 M☉ |
| Bolometric Luminosity | 6.377 L☉ |
| Metallicity [Fe/H] | 0.220 dex |
| Stellar Age | 4.360 Gyr |
| Apparent Magnitude | V: 7.520 · G: 7.257 |
| System Architecture | 1 Star, 2 Planets |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 3.584000 AU |
| Orbital Period | 2149 days |
| Mean Orbital Velocity | 18.1 km/s |
| Orbital Eccentricity (e) | 0.09900 |
| Orbital Inclination (i) | — |
| Mean Bulk Density | 2.89 g/cm³ (105.2 km/s vesc) |
| Insolation Flux | 0.5026 S⊕ (~684 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 289.600 LY (88.805 pc) |