K2-289 b
Astrophysical Synthesis & Habitability Characterization
K2-289 b is a confirmed gas giant exoplanet orbiting the star K2-289, located approximately 894.6 light-years (274.3 parsecs) from the Solar System. First announced in 2019 by K2 using the Transit detection technique (producing an estimated primary transit depth of 0.6625% across the stellar disk), this world measures 9.1 Earth radii (0.81 Jupiter radii) and has a measured mass of 61 Earth masses (0.19 Jupiter masses). Combining its mass and radius yields a mean bulk density of 0.45 g/cm³ (a low bulk density dominated by an extended hydrogen-helium gaseous envelope), a surface gravity of 0.74 g⊕ (7.26 m/s²), and an escape velocity of 29 km/s.
In its orbital architecture around K2-289, K2-289 b completes one full revolution every 13.157 Earth days at a semi-major axis of 0.107 AU (orbiting interior to Mercury's 0.387 AU benchmark in the Solar System). Its mean orbital velocity is approximately 88.5 km/s (compared to Earth's 29.8 km/s).
⚠️ Thermal Regime (Irradiated / Hot Zone): At an equilibrium temperature of 753 K (+480°C / +896°F) and receiving 27.32 S⊕ (~37,180 W/m²), K2-289 b orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star K2-289 is classified as a stellar host with an effective photospheric temperature of 5,529 K, a radius of 1.025 R☉, a mass of 0.953 M☉, an estimated bolometric luminosity of 0.881 L☉. Stellar evolution modeling indicates a metallicity of [Fe/H] = 0.162 dex (metal-rich relative to the Sun). From Earth, K2-289 shines at apparent V-band magnitude 14.81 (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: K2 · Catalogue Source: NASA Exoplanet Archive (IPAC / Caltech).
☀️ Host Star Telemetry
| Host Star Name | K2-289 |
| Spectral Type | Unclassified |
| Effective Temp (Teff) | 5,529 K |
| Stellar Radius | 1.0250 R☉ |
| Stellar Mass | 0.9530 M☉ |
| Bolometric Luminosity | 0.881 L☉ |
| Metallicity [Fe/H] | 0.162 dex |
| Stellar Age | — |
| Apparent Magnitude | V: 14.810 · G: 13.794 |
| System Architecture | 1 Star, 1 Planet |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.107000 AU |
| Orbital Period | 13.157 days |
| Mean Orbital Velocity | 88.5 km/s |
| Orbital Eccentricity (e) | Circular (0.00) |
| Orbital Inclination (i) | 88.4800° |
| Mean Bulk Density | 0.45 g/cm³ (29 km/s vesc) |
| Insolation Flux | 27.3178 S⊕ (~37,180 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 894.600 LY (274.300 pc) |