HD 74698 b
Astrophysical Synthesis & Habitability Characterization
HD 74698 b is a confirmed sub-neptune exoplanet orbiting the star HD 74698, located approximately 169.8 light-years (52.07 parsecs) from the Solar System. First announced in 2023 by La Silla Observatory using the Radial Velocity detection technique (measuring periodic Doppler reflex motion in the host star's spectrum), this world measures 5.12 Earth radii (0.46 Jupiter radii) and has a measured mass of 23 Earth masses. Combining its mass and radius yields a mean bulk density of 0.94 g/cm³ (a low bulk density dominated by an extended hydrogen-helium gaseous envelope), a surface gravity of 0.88 g⊕ (8.63 m/s²), and an escape velocity of 23.7 km/s.
In its orbital architecture around HD 74698, HD 74698 b completes one full revolution every 15.017 Earth days at a semi-major axis of 0.121 AU (orbiting interior to Mercury's 0.387 AU benchmark in the Solar System). Its mean orbital velocity is approximately 87.7 km/s (compared to Earth's 29.8 km/s). Its moderate orbital eccentricity of e = 0.1 carries the world between 0.1089 AU at periapsis and 0.1331 AU at apoapsis, driving measurable seasonal insolation cycles.
⚠️ Thermal Regime (Irradiated / Hot Zone): At an equilibrium temperature of 926 K (+653°C / +1207°F) and receiving 123.00 S⊕ (~167,403 W/m²), HD 74698 b orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star HD 74698 is classified as a solar-type yellow star of spectral type G5 V with an effective photospheric temperature of 5,783 K, a radius of 1.333 R☉, a mass of 1.039 M☉, an estimated bolometric luminosity of 1.783 L☉. Stellar evolution modeling indicates an estimated stellar age of 7.847 Gyr and a metallicity of [Fe/H] = 0.07 dex (metal-rich relative to the Sun). From Earth, HD 74698 shines at apparent V-band magnitude 7.78 (accessible to binoculars and small amateur telescopes) in the Southern celestial hemisphere. The HD 74698 system is a multi-planet architecture hosting 2 confirmed worlds, with HD 74698 b sharing its stellar neighborhood alongside HD 74698 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: La Silla Observatory · Catalogue Source: NASA Exoplanet Archive (IPAC / Caltech).
☀️ Host Star Telemetry
| Host Star Name | HD 74698 |
| Spectral Type | G5 V |
| Effective Temp (Teff) | 5,783 K |
| Stellar Radius | 1.3330 R☉ |
| Stellar Mass | 1.0390 M☉ |
| Bolometric Luminosity | 1.783 L☉ |
| Metallicity [Fe/H] | 0.070 dex |
| Stellar Age | 7.847 Gyr |
| Apparent Magnitude | V: 7.780 · G: 7.610 |
| System Architecture | 1 Star, 2 Planets |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.121000 AU |
| Orbital Period | 15.017 days |
| Mean Orbital Velocity | 87.7 km/s |
| Orbital Eccentricity (e) | 0.10000 |
| Orbital Inclination (i) | — |
| Mean Bulk Density | 0.94 g/cm³ (23.7 km/s vesc) |
| Insolation Flux | 123.0000 S⊕ (~167,403 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 169.800 LY (52.065 pc) |