V1298 Tau c
Astrophysical Synthesis & Habitability Characterization
V1298 Tau c is a confirmed sub-neptune exoplanet orbiting the star V1298 Tau, located approximately 352.9 light-years (108.2 parsecs) from the Solar System. First announced in 2019 by K2 using the Transit detection technique (producing an estimated primary transit depth of 0.1245% across the stellar disk), this world measures 5.08 Earth radii (0.45 Jupiter radii) and has a measured mass of 4.7 Earth masses. Combining its mass and radius yields a mean bulk density of 0.2 g/cm³ (a low bulk density dominated by an extended hydrogen-helium gaseous envelope), a surface gravity of 0.18 g⊕ (1.77 m/s²), and an escape velocity of 10.8 km/s.
In its orbital architecture around V1298 Tau, V1298 Tau c completes one full revolution every 8.249 Earth days at a semi-major axis of 0.0824 AU (orbiting interior to Mercury's 0.387 AU benchmark in the Solar System). Its mean orbital velocity is approximately 108.7 km/s (compared to Earth's 29.8 km/s). With a near-circular eccentricity of e = 0.0094 (ranging from 0.0816 AU at periapsis to 0.0832 AU at apoapsis), the planet experiences minimal orbital distance variation.
⚠️ Thermal Regime (Irradiated / Hot Zone): At an equilibrium temperature of 953 K (+680°C / +1256°F) and receiving 146.00 S⊕ (~198,706 W/m²), V1298 Tau c orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star V1298 Tau is classified as an orange K-type star of spectral type K1 with an effective photospheric temperature of 4,970 K, a radius of 1.32 R☉, a mass of 1.1 M☉, an estimated bolometric luminosity of 0.954 L☉. Stellar evolution modeling indicates an estimated stellar age of 0.02 Gyr and a metallicity of [Fe/H] = 0.1 dex (metal-rich relative to the Sun). From Earth, V1298 Tau shines at apparent V-band magnitude 10.115 (faint and requiring research-grade or CCD telescopic photometry) in the Northern celestial hemisphere. The V1298 Tau system is a multi-planet architecture hosting 4 confirmed worlds, with V1298 Tau c sharing its stellar neighborhood alongside V1298 Tau d, V1298 Tau b, V1298 Tau e.
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: K2 · Catalogue Source: NASA Exoplanet Archive (IPAC / Caltech).
☀️ Host Star Telemetry
| Host Star Name | V1298 Tau |
| Spectral Type | K1 |
| Effective Temp (Teff) | 4,970 K |
| Stellar Radius | 1.3200 R☉ |
| Stellar Mass | 1.1000 M☉ |
| Bolometric Luminosity | 0.954 L☉ |
| Metallicity [Fe/H] | 0.100 dex |
| Stellar Age | 0.020 Gyr |
| Apparent Magnitude | V: 10.115 · G: 10.070 |
| System Architecture | 3 Stars, 4 Planets |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.082400 AU |
| Orbital Period | 8.249 days |
| Mean Orbital Velocity | 108.7 km/s |
| Orbital Eccentricity (e) | 0.00940 |
| Orbital Inclination (i) | 88.4900° |
| Mean Bulk Density | 0.2 g/cm³ (10.8 km/s vesc) |
| Insolation Flux | 146.0000 S⊕ (~198,706 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 352.900 LY (108.199 pc) |