KMT-2021-BLG-1689L b
Astrophysical Synthesis & Habitability Characterization
KMT-2021-BLG-1689L b is a confirmed gas giant exoplanet orbiting the star KMT-2021-BLG-1689L, located approximately 23483.2 light-years (7200 parsecs) from the Solar System. First announced in 2022 by KMTNet using the Microlensing detection technique (detected via relativistic gravitational lensing of a background source star), this world measures 7.71 Earth radii (0.69 Jupiter radii) and has a measured mass of 46 Earth masses (0.14 Jupiter masses). Combining its mass and radius yields a mean bulk density of 0.55 g/cm³ (a low bulk density dominated by an extended hydrogen-helium gaseous envelope), a surface gravity of 0.77 g⊕ (7.55 m/s²), and an escape velocity of 27.3 km/s.
☁️ Atmospheric Regime (Volatile / Gas Envelope): With a radius of 7.710 R⊕, KMT-2021-BLG-1689L b exceeds the empirical ~1.8–2.2 R⊕ Fulton radius valley threshold, indicating a substantial hydrogen-helium or supercritical volatile envelope without a conventional solid terrestrial surface.
The host star KMT-2021-BLG-1689L is classified as a stellar host with an effective photospheric temperature of 4,570 K, a mass of 0.58 M☉.
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: KMTNet · Catalogue Source: NASA Exoplanet Archive (IPAC / Caltech).
☀️ Host Star Telemetry
| Host Star Name | KMT-2021-BLG-1689L |
| Spectral Type | Unclassified |
| Effective Temp (Teff) | 4,570 K |
| Stellar Radius | — |
| Stellar Mass | 0.5800 M☉ |
| Metallicity [Fe/H] | — |
| Stellar Age | — |
| Apparent Magnitude | — |
| System Architecture | 1 Star, 1 Planet |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 2.500000 AU |
| Orbital Period | — |
| Orbital Eccentricity (e) | Circular (0.00) |
| Orbital Inclination (i) | — |
| Mean Bulk Density | 0.55 g/cm³ (27.3 km/s vesc) |
| Insolation Flux | — |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 23483.200 LY (7200.000 pc) |