GJ 724 b
Astrophysical Synthesis & Habitability Characterization
GJ 724 b is a confirmed sub-neptune exoplanet orbiting the star GJ 724, located approximately 55.3 light-years (16.97 parsecs) from the Solar System. First announced in 2023 by Calar Alto Observatory using the Radial Velocity detection technique (measuring periodic Doppler reflex motion in the host star's spectrum), this world measures 3.27 Earth radii (0.29 Jupiter radii) and has a measured mass of 10.75 Earth masses. Combining its mass and radius yields a mean bulk density of 1.7 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 20.3 km/s.
In its orbital architecture around GJ 724, GJ 724 b completes one full revolution every 5.101 Earth days at a semi-major axis of 0.04685 AU (an ultra-close orbit less than one-seventh of Mercury's 0.387 AU distance from the Sun, where strong stellar tidal forces typically induce synchronous rotation). Its mean orbital velocity is approximately 99.9 km/s (compared to Earth's 29.8 km/s). The planet follows a highly eccentric trajectory (e = 0.577, swinging from 0.0198 AU at periapsis out to 0.0739 AU at apoapsis), pointing to past dynamical scattering or secular gravitational perturbations.
⚠️ Thermal Regime (Irradiated / Hot Zone): At an equilibrium temperature of 611 K (+338°C / +640°F) and receiving 23.32 S⊕ (~31,739 W/m²), GJ 724 b orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star GJ 724 is classified as a low-mass red dwarf of spectral type M1.0 V with an effective photospheric temperature of 3,799 K, a radius of 0.5223 R☉, a mass of 0.5271 M☉, an estimated bolometric luminosity of 0.051 L☉. Stellar evolution modeling indicates a metallicity of [Fe/H] = -0.02 dex (near-solar heavy-element abundance). From Earth, GJ 724 shines at apparent V-band magnitude 10.638 (faint and requiring research-grade or CCD telescopic photometry) in the Southern celestial hemisphere.
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: Calar Alto Observatory · Catalogue Source: NASA Exoplanet Archive (IPAC / Caltech).
☀️ Host Star Telemetry
| Host Star Name | GJ 724 |
| Spectral Type | M1.0 V |
| Effective Temp (Teff) | 3,799 K |
| Stellar Radius | 0.5223 R☉ |
| Stellar Mass | 0.5271 M☉ |
| Bolometric Luminosity | 0.051 L☉ |
| Metallicity [Fe/H] | -0.020 dex |
| Stellar Age | — |
| Apparent Magnitude | V: 10.638 · G: 9.769 |
| System Architecture | 1 Star, 1 Planet |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.046850 AU |
| Orbital Period | 5.101 days |
| Mean Orbital Velocity | 99.9 km/s |
| Orbital Eccentricity (e) | 0.57700 |
| Orbital Inclination (i) | — |
| Mean Bulk Density | 1.7 g/cm³ (20.3 km/s vesc) |
| Insolation Flux | 23.3200 S⊕ (~31,739 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 55.300 LY (16.966 pc) |