Kepler-289 d
Astrophysical Synthesis & Habitability Characterization
Kepler-289 d is a confirmed sub-neptune exoplanet orbiting the star Kepler-289, located approximately 2297.6 light-years (704.44 parsecs) from the Solar System. First announced in 2014 by Kepler using the Transit detection technique (producing an estimated primary transit depth of 0.0772% across the stellar disk), this world measures 3.03 Earth radii (0.27 Jupiter radii) and has a measured mass of 5.33 Earth masses. Combining its mass and radius yields a mean bulk density of 1.06 g/cm³ (a low bulk density dominated by an extended hydrogen-helium gaseous envelope), a surface gravity of 0.58 g⊕ (5.69 m/s²), and an escape velocity of 14.8 km/s.
In its orbital architecture around Kepler-289, Kepler-289 d completes one full revolution every 66.028 Earth days at a semi-major axis of 0.33 AU (orbiting interior to Mercury's 0.387 AU benchmark in the Solar System). Its mean orbital velocity is approximately 54.4 km/s (compared to Earth's 29.8 km/s).
⚠️ Thermal Regime (Irradiated / Hot Zone): At an equilibrium temperature of 503 K (+230°C / +446°F) and receiving 10.57 S⊕ (~14,382 W/m²), Kepler-289 d orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star Kepler-289 is classified as a stellar host with an effective photospheric temperature of 5,990 K, a radius of 1 R☉, a mass of 1.08 M☉, an estimated bolometric luminosity of 1.155 L☉. Stellar evolution modeling indicates an estimated stellar age of 0.65 Gyr and a metallicity of [Fe/H] = 0.05 dex (near-solar heavy-element abundance). From Earth, Kepler-289 shines at apparent V-band magnitude 14.142 (faint and requiring research-grade or CCD telescopic photometry) in the Northern celestial hemisphere. The Kepler-289 system is a multi-planet architecture hosting 4 confirmed worlds, with Kepler-289 d sharing its stellar neighborhood alongside Kepler-289 b, Kepler-289 c, Kepler-289 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: Kepler · Catalogue Source: NASA Exoplanet Archive (IPAC / Caltech).
☀️ Host Star Telemetry
| Host Star Name | Kepler-289 |
| Spectral Type | Unclassified |
| Effective Temp (Teff) | 5,990 K |
| Stellar Radius | 1.0000 R☉ |
| Stellar Mass | 1.0800 M☉ |
| Bolometric Luminosity | 1.155 L☉ |
| Metallicity [Fe/H] | 0.050 dex |
| Stellar Age | 0.650 Gyr |
| Apparent Magnitude | V: 14.142 · G: 13.963 |
| System Architecture | 1 Star, 4 Planets |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.330000 AU |
| Orbital Period | 66.028 days |
| Mean Orbital Velocity | 54.4 km/s |
| Orbital Eccentricity (e) | Circular (0.00) |
| Orbital Inclination (i) | 89.3100° |
| Mean Bulk Density | 1.06 g/cm³ (14.8 km/s vesc) |
| Insolation Flux | 10.5675 S⊕ (~14,382 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 2297.600 LY (704.438 pc) |