HD 7924 d

Astrophysical Synthesis & Habitability Characterization

HD 7924 d is a confirmed gas giant exoplanet orbiting the star HD 7924, located approximately 55.4 light-years (16.99 parsecs) from the Solar System. First announced in 2015 by W. M. Keck Observatory using the Radial Velocity detection technique (measuring periodic Doppler reflex motion in the host star's spectrum), this world has a minimum or true mass of 1568.165 Earth masses (4.93 M♃), while its physical transit radius has not yet been geometrically observed.

In its orbital architecture around HD 7924, HD 7924 d completes one full revolution every 24.451 Earth days at a semi-major axis of 0.1551 AU (orbiting interior to Mercury's 0.387 AU benchmark in the Solar System). Its mean orbital velocity is approximately 69 km/s (compared to Earth's 29.8 km/s). Its moderate orbital eccentricity of e = 0.21 carries the world between 0.1225 AU at periapsis and 0.1877 AU at apoapsis, driving measurable seasonal insolation cycles.

⚠️ Thermal Regime (Irradiated / Hot Zone): At an equilibrium temperature of 499 K (+226°C / +439°F) and receiving 15.17 S⊕ (~20,646 W/m²), HD 7924 d orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.

The host star HD 7924 is classified as an orange K-type star of spectral type K0.5 V with an effective photospheric temperature of 5,075 K, a radius of 0.7821 R☉, a mass of 0.832 M☉, an estimated bolometric luminosity of 0.364 L☉. Stellar evolution modeling indicates an estimated stellar age of 0.88 Gyr and a metallicity of [Fe/H] = -0.15 dex (metal-poor relative to the Sun). From Earth, HD 7924 shines at apparent V-band magnitude 7.179 (accessible to binoculars and small amateur telescopes) in the Northern celestial hemisphere. The HD 7924 system is a multi-planet architecture hosting 3 confirmed worlds, with HD 7924 d sharing its stellar neighborhood alongside HD 7924 b, HD 7924 c.

Discovery Facility: W. M. Keck Observatory · Catalogue Source: NASA Exoplanet Archive (IPAC / Caltech).