KOI-984 b
Astrophysical Synthesis & Habitability Characterization
KOI-984 b is a confirmed sub-neptune exoplanet orbiting the star KOI-984, located approximately 824.1 light-years (252.67 parsecs) from the Solar System. First announced in 2022 by Kepler using the Transit detection technique (producing an estimated primary transit depth of 0.2323% across the stellar disk), this world measures 4.3 Earth radii (0.38 Jupiter radii) and has a measured mass of 17.1 Earth masses. Combining its mass and radius yields a mean bulk density of 1.19 g/cm³ (a low bulk density dominated by an extended hydrogen-helium gaseous envelope), a surface gravity of 0.92 g⊕ (9.02 m/s²), and an escape velocity of 22.3 km/s.
In its orbital architecture around KOI-984, KOI-984 b completes one full revolution every 4.288 Earth days at a semi-major axis of 0.0504 AU (orbiting interior to Mercury's 0.387 AU benchmark in the Solar System). Its mean orbital velocity is approximately 127.9 km/s (compared to Earth's 29.8 km/s). Its moderate orbital eccentricity of e = 0.12 carries the world between 0.0444 AU at periapsis and 0.0564 AU at apoapsis, driving measurable seasonal insolation cycles.
⚠️ Thermal Regime (Irradiated / Hot Zone): At an equilibrium temperature of 1022 K (+749°C / +1380°F) and receiving 186.31 S⊕ (~253,568 W/m²), KOI-984 b orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star KOI-984 is classified as a stellar host with an effective photospheric temperature of 5,295 K, a radius of 0.818 R☉, a mass of 0.928 M☉, an estimated bolometric luminosity of 0.472 L☉. Stellar evolution modeling indicates an estimated stellar age of 1.3 Gyr and a metallicity of [Fe/H] = 0.12 dex (metal-rich relative to the Sun). From Earth, KOI-984 shines at apparent V-band magnitude 12.795 (faint and requiring research-grade or CCD telescopic photometry) in the Northern celestial hemisphere. The KOI-984 system is a multi-planet architecture hosting 2 confirmed worlds, with KOI-984 b sharing its stellar neighborhood alongside KOI-984 c.
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: Kepler · Catalogue Source: NASA Exoplanet Archive (IPAC / Caltech).
☀️ Host Star Telemetry
| Host Star Name | KOI-984 |
| Spectral Type | Unclassified |
| Effective Temp (Teff) | 5,295 K |
| Stellar Radius | 0.8180 R☉ |
| Stellar Mass | 0.9280 M☉ |
| Bolometric Luminosity | 0.472 L☉ |
| Metallicity [Fe/H] | 0.120 dex |
| Stellar Age | 1.300 Gyr |
| Apparent Magnitude | V: 12.795 |
| System Architecture | 1 Star, 2 Planets |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.050400 AU |
| Orbital Period | 4.288 days |
| Mean Orbital Velocity | 127.9 km/s |
| Orbital Eccentricity (e) | 0.12000 |
| Orbital Inclination (i) | 88.9300° |
| Mean Bulk Density | 1.19 g/cm³ (22.3 km/s vesc) |
| Insolation Flux | 186.3100 S⊕ (~253,568 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 824.100 LY (252.667 pc) |