KOI-4978 b
Astrophysical Synthesis & Habitability Characterization
KOI-4978 b is a confirmed sub-earth exoplanet orbiting the star KOI-4978, located approximately 3053.9 light-years (936.34 parsecs) from the Solar System. First announced in 2024 by Kepler using the Transit detection technique (producing an estimated primary transit depth of 0.0044% across the stellar disk), this world measures 0.7 Earth radii and has a measured mass of 0.271 Earth masses. Combining its mass and radius yields a mean bulk density of 4.36 g/cm³ (a terrestrial silicate-iron composition comparable to Earth (5.51 g/cm³)), a surface gravity of 0.55 g⊕ (5.39 m/s²), and an escape velocity of 7 km/s.
In its orbital architecture around KOI-4978, KOI-4978 b completes one full revolution every 0.942 Earth days.
ℹ️ Thermal & Atmospheric Regime: Current photometric and spectroscopic constraints for KOI-4978 b place it outside the conservative habitable zone definition pending further atmospheric characterization.
The host star KOI-4978 is classified as a solar-type yellow star of spectral type G with an effective photospheric temperature of 5,050 K, a radius of 0.966 R☉, a mass of 0.859 M☉, an estimated bolometric luminosity of 0.545 L☉. Stellar evolution modeling indicates an estimated stellar age of 1.48 Gyr and a metallicity of [Fe/H] = 0.18 dex (metal-rich relative to the Sun). From Earth, KOI-4978 shines at apparent V-band magnitude 15.633 (faint and requiring research-grade or CCD telescopic photometry) in the Northern celestial hemisphere.
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-4978 |
| Spectral Type | G |
| Effective Temp (Teff) | 5,050 K |
| Stellar Radius | 0.9660 R☉ |
| Stellar Mass | 0.8590 M☉ |
| Bolometric Luminosity | 0.545 L☉ |
| Metallicity [Fe/H] | 0.180 dex |
| Stellar Age | 1.480 Gyr |
| Apparent Magnitude | V: 15.633 · G: 15.248 |
| System Architecture | 1 Star, 1 Planet |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | — |
| Orbital Period | 0.942 days |
| Orbital Eccentricity (e) | Circular (0.00) |
| Orbital Inclination (i) | — |
| Mean Bulk Density | 4.36 g/cm³ (7 km/s vesc) |
| Insolation Flux | — |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 3053.900 LY (936.341 pc) |