HD 22946 d
Astrophysical Synthesis & Habitability Characterization
HD 22946 d is a confirmed sub-neptune exoplanet orbiting the star HD 22946, located approximately 204.8 light-years (62.78 parsecs) from the Solar System. First announced in 2023 by Transiting Exoplanet Survey Satellite (TESS) using the Transit detection technique (producing an estimated primary transit depth of 0.0458% across the stellar disk), this world measures 2.607 Earth radii and has a measured mass of 26.57 Earth masses. Combining its mass and radius yields a mean bulk density of 8.27 g/cm³ (an iron-enriched, high-compression rocky core), a surface gravity of 3.91 g⊕ (38.34 m/s²), and an escape velocity of 35.7 km/s.
In its orbital architecture around HD 22946, HD 22946 d completes one full revolution every 47.425 Earth days at a semi-major axis of 0.2958 AU (orbiting interior to Mercury's 0.387 AU benchmark in the Solar System). Its mean orbital velocity is approximately 67.9 km/s (compared to Earth's 29.8 km/s).
⚠️ Thermal Regime (Irradiated / Hot Zone): At an equilibrium temperature of 546 K (+273°C / +523°F) and receiving 18.56 S⊕ (~25,262 W/m²), HD 22946 d orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star HD 22946 is classified as a warm F-type star of spectral type F7/F8V with an effective photospheric temperature of 6,169 K, a radius of 1.117 R☉, a mass of 1.098 M☉, an estimated bolometric luminosity of 1.621 L☉. Stellar evolution modeling indicates an estimated stellar age of 2.5 Gyr and a metallicity of [Fe/H] = -0.08 dex (near-solar heavy-element abundance). From Earth, HD 22946 shines at apparent V-band magnitude 8.27 (accessible to binoculars and small amateur telescopes) in the Southern celestial hemisphere. The HD 22946 system is a multi-planet architecture hosting 3 confirmed worlds, with HD 22946 d sharing its stellar neighborhood alongside TOI-411 b, TOI-411 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: Transiting Exoplanet Survey Satellite (TESS) · Catalogue Source: NASA Exoplanet Archive (IPAC / Caltech).
☀️ Host Star Telemetry
| Host Star Name | HD 22946 |
| Spectral Type | F7/F8V |
| Effective Temp (Teff) | 6,169 K |
| Stellar Radius | 1.1170 R☉ |
| Stellar Mass | 1.0980 M☉ |
| Bolometric Luminosity | 1.621 L☉ |
| Metallicity [Fe/H] | -0.080 dex |
| Stellar Age | 2.500 Gyr |
| Apparent Magnitude | V: 8.270 · G: 8.128 |
| System Architecture | 1 Star, 3 Planets |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.295800 AU |
| Orbital Period | 47.425 days |
| Mean Orbital Velocity | 67.9 km/s |
| Orbital Eccentricity (e) | Circular (0.00) |
| Orbital Inclination (i) | — |
| Mean Bulk Density | 8.27 g/cm³ (35.7 km/s vesc) |
| Insolation Flux | 18.5610 S⊕ (~25,262 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 204.800 LY (62.779 pc) |