HD 115404 A b
Astrophysical Synthesis & Habitability Characterization
HD 115404 A b is a confirmed gas giant exoplanet orbiting the star HD 115404 A, located approximately 35.8 light-years (10.98 parsecs) from the Solar System. First announced in 2022 by Multiple Observatories using the Radial Velocity detection technique (measuring periodic Doppler reflex motion in the host star's spectrum), this world measures 6.09 Earth radii (0.54 Jupiter radii) and has a measured mass of 30.829 Earth masses (0.1 Jupiter masses). Combining its mass and radius yields a mean bulk density of 0.75 g/cm³ (a low bulk density dominated by an extended hydrogen-helium gaseous envelope), a surface gravity of 0.83 g⊕ (8.14 m/s²), and an escape velocity of 25.2 km/s.
In its orbital architecture around HD 115404 A, HD 115404 A b completes one full revolution every 10.495 Earth days at a semi-major axis of 0.088 AU (orbiting interior to Mercury's 0.387 AU benchmark in the Solar System). Its mean orbital velocity is approximately 91.2 km/s (compared to Earth's 29.8 km/s). Its moderate orbital eccentricity of e = 0.232 carries the world between 0.0676 AU at periapsis and 0.1084 AU at apoapsis, driving measurable seasonal insolation cycles.
⚠️ Thermal Regime (Irradiated / Hot Zone): At an equilibrium temperature of 696 K (+423°C / +793°F) and receiving 39.02 S⊕ (~53,112 W/m²), HD 115404 A b orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star HD 115404 A is classified as an orange K-type star of spectral type K2V with an effective photospheric temperature of 5,019 K, a radius of 0.727 R☉, a mass of 0.83 M☉, an estimated bolometric luminosity of 0.301 L☉. Stellar evolution modeling indicates a metallicity of [Fe/H] = -0.157 dex (metal-poor relative to the Sun). From Earth, HD 115404 A shines at apparent V-band magnitude 6.501 (accessible to binoculars and small amateur telescopes) in the Northern celestial hemisphere. The HD 115404 A system is a multi-planet architecture hosting 2 confirmed worlds, with HD 115404 A b sharing its stellar neighborhood alongside HD 115404 A c.
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 115404 A |
| Spectral Type | K2V |
| Effective Temp (Teff) | 5,019 K |
| Stellar Radius | 0.7270 R☉ |
| Stellar Mass | 0.8300 M☉ |
| Bolometric Luminosity | 0.301 L☉ |
| Metallicity [Fe/H] | -0.157 dex |
| Stellar Age | — |
| Apparent Magnitude | V: 6.501 · G: 6.286 |
| System Architecture | 1 Star, 2 Planets |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.088000 AU |
| Orbital Period | 10.495 days |
| Mean Orbital Velocity | 91.2 km/s |
| Orbital Eccentricity (e) | 0.23200 |
| Orbital Inclination (i) | — |
| Mean Bulk Density | 0.75 g/cm³ (25.2 km/s vesc) |
| Insolation Flux | 39.0242 S⊕ (~53,112 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 35.800 LY (10.982 pc) |