HD 31527 b
Astrophysical Synthesis & Habitability Characterization
HD 31527 b is a confirmed sub-neptune exoplanet orbiting the star HD 31527, located approximately 125.4 light-years (38.45 parsecs) from the Solar System. First announced in 2019 by La Silla Observatory using the Radial Velocity detection technique (measuring periodic Doppler reflex motion in the host star's spectrum), this world measures 3.22 Earth radii (0.29 Jupiter radii) and has a measured mass of 10.47 Earth masses. Combining its mass and radius yields a mean bulk density of 1.73 g/cm³ (a low bulk density dominated by an extended hydrogen-helium gaseous envelope), a surface gravity of 1.01 g⊕ (9.9 m/s²), and an escape velocity of 20.2 km/s.
In its orbital architecture around HD 31527, HD 31527 b completes one full revolution every 16.554 Earth days at a semi-major axis of 0.1254 AU (orbiting interior to Mercury's 0.387 AU benchmark in the Solar System). Its mean orbital velocity is approximately 82.4 km/s (compared to Earth's 29.8 km/s). Its moderate orbital eccentricity of e = 0.1 carries the world between 0.1129 AU at periapsis and 0.1379 AU at apoapsis, driving measurable seasonal insolation cycles.
⚠️ Thermal Regime (Irradiated / Hot Zone): At an equilibrium temperature of 832 K (+559°C / +1038°F) and receiving 76.31 S⊕ (~103,859 W/m²), HD 31527 b orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star HD 31527 is classified as a solar-type yellow star of spectral type G2 V with an effective photospheric temperature of 5,898 K, a radius of 1.0737 R☉, a mass of 0.96 M☉, an estimated bolometric luminosity of 1.252 L☉. Stellar evolution modeling indicates a metallicity of [Fe/H] = -0.17 dex (metal-poor relative to the Sun). From Earth, HD 31527 shines at apparent V-band magnitude 7.49 (accessible to binoculars and small amateur telescopes) in the Southern celestial hemisphere. The HD 31527 system is a multi-planet architecture hosting 3 confirmed worlds, with HD 31527 b sharing its stellar neighborhood alongside HD 31527 c, HD 31527 d.
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: La Silla Observatory · Catalogue Source: NASA Exoplanet Archive (IPAC / Caltech).
☀️ Host Star Telemetry
| Host Star Name | HD 31527 |
| Spectral Type | G2 V |
| Effective Temp (Teff) | 5,898 K |
| Stellar Radius | 1.0737 R☉ |
| Stellar Mass | 0.9600 M☉ |
| Bolometric Luminosity | 1.252 L☉ |
| Metallicity [Fe/H] | -0.170 dex |
| Stellar Age | — |
| Apparent Magnitude | V: 7.490 · G: 7.332 |
| System Architecture | 1 Star, 3 Planets |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.125400 AU |
| Orbital Period | 16.554 days |
| Mean Orbital Velocity | 82.4 km/s |
| Orbital Eccentricity (e) | 0.10000 |
| Orbital Inclination (i) | — |
| Mean Bulk Density | 1.73 g/cm³ (20.2 km/s vesc) |
| Insolation Flux | 76.3108 S⊕ (~103,859 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 125.400 LY (38.447 pc) |