HD 202696 c

Astrophysical Synthesis & Habitability Characterization

HD 202696 c is a confirmed gas giant exoplanet orbiting the star HD 202696, located approximately 615 light-years (188.55 parsecs) from the Solar System. First announced in 2019 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 592.435 Earth masses (1.86 M♃), while its physical transit radius has not yet been geometrically observed.

In its orbital architecture around HD 202696, HD 202696 c completes one full revolution every 946.6 Earth days (2.59Julian years) at a semi-major axis of 2.342 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 26.9 km/s (compared to Earth's 29.8 km/s). With a near-circular eccentricity of e = 0.028 (ranging from 2.2764 AU at periapsis to 2.4076 AU at apoapsis), the planet experiences minimal orbital distance variation.

⚠️ Thermal Regime (Irradiated / Hot Zone): At an equilibrium temperature of 403 K (+130°C / +266°F) and receiving 4.27 S⊕ (~5,806 W/m²), HD 202696 c orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.

The host star HD 202696 is classified as an orange K-type star of spectral type K0 III-IV with an effective photospheric temperature of 5,040 K, a radius of 6.43 R☉, a mass of 1.91 M☉, an estimated bolometric luminosity of 23.935 L☉. Stellar evolution modeling indicates an estimated stellar age of 1.32 Gyr and a metallicity of [Fe/H] = 0.02 dex (near-solar heavy-element abundance). From Earth, HD 202696 shines at apparent V-band magnitude 8.23 (accessible to binoculars and small amateur telescopes) in the Northern celestial hemisphere. The HD 202696 system is a multi-planet architecture hosting 2 confirmed worlds, with HD 202696 c sharing its stellar neighborhood alongside HD 202696 b.

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