Kepler-1987 d
Astrophysical Synthesis & Habitability Characterization
Kepler-1987 d is a confirmed sub-neptune exoplanet orbiting the star Kepler-1987, located approximately 1942.9 light-years (595.68 parsecs) from the Solar System. First announced in 2023 by Kepler using the Transit detection technique (producing an estimated primary transit depth of 0.1167% across the stellar disk), this world measures 2.66 Earth radii and has a measured mass of 7.56 Earth masses. Combining its mass and radius yields a mean bulk density of 2.21 g/cm³ (an intermediate density indicative of a deep water-ice mantle or dense volatile envelope), a surface gravity of 1.07 g⊕ (10.49 m/s²), and an escape velocity of 18.9 km/s.
In its orbital architecture around Kepler-1987, Kepler-1987 d completes one full revolution every 5.645 Earth days at a semi-major axis of 0.0571 AU (orbiting interior to Mercury's 0.387 AU benchmark in the Solar System). Its mean orbital velocity is approximately 110 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 744 K (+471°C / +880°F) and receiving 72.38 S⊕ (~98,509 W/m²), Kepler-1987 d orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star Kepler-1987 is classified as a stellar host with an effective photospheric temperature of 4,769 K, a radius of 0.714 R☉, a mass of 0.799 M☉, an estimated bolometric luminosity of 0.237 L☉. Stellar evolution modeling indicates a metallicity of [Fe/H] = 0.12 dex (metal-rich relative to the Sun). From Earth, Kepler-1987 shines at apparent V-band magnitude 15.477 (faint and requiring research-grade or CCD telescopic photometry) in the Northern celestial hemisphere. The Kepler-1987 system is a multi-planet architecture hosting 4 confirmed worlds, with Kepler-1987 d sharing its stellar neighborhood alongside Kepler-1987 b, Kepler-1987 c, Kepler-1987 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-1987 |
| Spectral Type | Unclassified |
| Effective Temp (Teff) | 4,769 K |
| Stellar Radius | 0.7140 R☉ |
| Stellar Mass | 0.7990 M☉ |
| Bolometric Luminosity | 0.237 L☉ |
| Metallicity [Fe/H] | 0.120 dex |
| Stellar Age | — |
| Apparent Magnitude | V: 15.477 · G: 15.505 |
| System Architecture | 1 Star, 4 Planets |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.057100 AU |
| Orbital Period | 5.645 days |
| Mean Orbital Velocity | 110 km/s |
| Orbital Eccentricity (e) | 0.00000 |
| Orbital Inclination (i) | 88.5700° |
| Mean Bulk Density | 2.21 g/cm³ (18.9 km/s vesc) |
| Insolation Flux | 72.3800 S⊕ (~98,509 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 1942.900 LY (595.683 pc) |