LTT 9779 b
Astrophysical Synthesis & Habitability Characterization
LTT 9779 b is a confirmed sub-neptune exoplanet orbiting the star LTT 9779, located approximately 262.4 light-years (80.44 parsecs) from the Solar System. First announced in 2020 by Transiting Exoplanet Survey Satellite (TESS) using the Transit detection technique (producing an estimated primary transit depth of 0.2079% across the stellar disk), this world measures 4.72 Earth radii (0.42 Jupiter radii) and has a measured mass of 29.32 Earth masses. Combining its mass and radius yields a mean bulk density of 1.54 g/cm³ (a low bulk density dominated by an extended hydrogen-helium gaseous envelope), a surface gravity of 1.32 g⊕ (12.94 m/s²), and an escape velocity of 27.9 km/s.
In its orbital architecture around LTT 9779, LTT 9779 b completes one full revolution every 0.792 Earth days at a semi-major axis of 0.01679 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 230.6 km/s (compared to Earth's 29.8 km/s). The orbit is modeled as circular (e = 0.00), maintaining a constant stellar distance throughout its year.
⚠️ Thermal Regime (Irradiated / Hot Zone): At an equilibrium temperature of 1978 K (+1705°C / +3101°F) and receiving 1,781.16 S⊕ (~2,424,153 W/m²), LTT 9779 b orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star LTT 9779 is classified as a solar-type yellow star of spectral type G7 V with an effective photospheric temperature of 5,443 K, a radius of 0.949 R☉, a mass of 1.02 M☉, an estimated bolometric luminosity of 0.709 L☉. Stellar evolution modeling indicates an estimated stellar age of 2 Gyr and a metallicity of [Fe/H] = 0.27 dex (metal-rich relative to the Sun). From Earth, LTT 9779 shines at apparent V-band magnitude 9.79 (accessible to binoculars and small amateur telescopes) 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: Transiting Exoplanet Survey Satellite (TESS) · Catalogue Source: NASA Exoplanet Archive (IPAC / Caltech).
☀️ Host Star Telemetry
| Host Star Name | LTT 9779 |
| Spectral Type | G7 V |
| Effective Temp (Teff) | 5,443 K |
| Stellar Radius | 0.9490 R☉ |
| Stellar Mass | 1.0200 M☉ |
| Bolometric Luminosity | 0.709 L☉ |
| Metallicity [Fe/H] | 0.270 dex |
| Stellar Age | 2.000 Gyr |
| Apparent Magnitude | V: 9.790 · G: 9.600 |
| System Architecture | 1 Star, 1 Planet |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.016790 AU |
| Orbital Period | 0.792 days |
| Mean Orbital Velocity | 230.6 km/s |
| Orbital Eccentricity (e) | 0.00000 |
| Orbital Inclination (i) | 76.3900° |
| Mean Bulk Density | 1.54 g/cm³ (27.9 km/s vesc) |
| Insolation Flux | 1781.1556 S⊕ (~2,424,153 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 262.400 LY (80.437 pc) |