Kepler-487 d
Astrophysical Synthesis & Habitability Characterization
Kepler-487 d is a confirmed sub-neptune exoplanet orbiting the star Kepler-487, located approximately 2845.2 light-years (872.34 parsecs) from the Solar System. First announced in 2021 by Kepler using the Transit detection technique (producing an estimated primary transit depth of 0.0823% across the stellar disk), this world measures 2.775 Earth radii and has a measured mass of 8.12 Earth masses. Combining its mass and radius yields a mean bulk density of 2.1 g/cm³ (an intermediate density indicative of a deep water-ice mantle or dense volatile envelope), a surface gravity of 1.05 g⊕ (10.3 m/s²), and an escape velocity of 19.1 km/s.
In its orbital architecture around Kepler-487, Kepler-487 d completes one full revolution every 2.418 Earth days at a semi-major axis of 0.03445 AU (an ultra-close orbit less than one-seventh of Mercury's 0.387 AU distance from the Sun, where strong stellar tidal forces typically induce synchronous rotation). Its mean orbital velocity is approximately 155 km/s (compared to Earth's 29.8 km/s). The orbit is modeled as circular (e = 0.00), maintaining a constant stellar distance throughout its year.
⚠️ Thermal Regime (Irradiated / Hot Zone): At an equilibrium temperature of 1226 K (+953°C / +1747°F) and receiving 550.80 S⊕ (~749,639 W/m²), Kepler-487 d orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star Kepler-487 is classified as a stellar host with an effective photospheric temperature of 5,422 K, a radius of 0.887 R☉, a mass of 0.874 M☉, an estimated bolometric luminosity of 0.61 L☉. Stellar evolution modeling indicates an estimated stellar age of 4.68 Gyr and a metallicity of [Fe/H] = 0.02 dex (near-solar heavy-element abundance). From Earth, Kepler-487 shines at apparent V-band magnitude 14.882 (faint and requiring research-grade or CCD telescopic photometry) in the Northern celestial hemisphere. The Kepler-487 system is a multi-planet architecture hosting 3 confirmed worlds, with Kepler-487 d sharing its stellar neighborhood alongside Kepler-487 b, Kepler-487 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 | Kepler-487 |
| Spectral Type | Unclassified |
| Effective Temp (Teff) | 5,422 K |
| Stellar Radius | 0.8870 R☉ |
| Stellar Mass | 0.8740 M☉ |
| Bolometric Luminosity | 0.61 L☉ |
| Metallicity [Fe/H] | 0.020 dex |
| Stellar Age | 4.680 Gyr |
| Apparent Magnitude | V: 14.882 · G: 15.065 |
| System Architecture | 1 Star, 3 Planets |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.034450 AU |
| Orbital Period | 2.418 days |
| Mean Orbital Velocity | 155 km/s |
| Orbital Eccentricity (e) | 0.00000 |
| Orbital Inclination (i) | 89.8900° |
| Mean Bulk Density | 2.1 g/cm³ (19.1 km/s vesc) |
| Insolation Flux | 550.8000 S⊕ (~749,639 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 2845.200 LY (872.343 pc) |