HD 73583 c
Astrophysical Synthesis & Habitability Characterization
HD 73583 c is a confirmed sub-neptune exoplanet orbiting the star HD 73583, located approximately 103 light-years (31.57 parsecs) from the Solar System. First announced in 2022 by Transiting Exoplanet Survey Satellite (TESS) using the Transit detection technique (producing an estimated primary transit depth of 0.1136% across the stellar disk), this world measures 2.39 Earth radii and has a measured mass of 9.7 Earth masses. Combining its mass and radius yields a mean bulk density of 3.92 g/cm³ (an intermediate density indicative of a deep water-ice mantle or dense volatile envelope), a surface gravity of 1.7 g⊕ (16.67 m/s²), and an escape velocity of 22.5 km/s.
In its orbital architecture around HD 73583, HD 73583 c completes one full revolution every 18.88 Earth days at a semi-major axis of 0.1242 AU (orbiting interior to Mercury's 0.387 AU benchmark in the Solar System). Its mean orbital velocity is approximately 71.6 km/s (compared to Earth's 29.8 km/s). Its moderate orbital eccentricity of e = 0.08 carries the world between 0.1143 AU at periapsis and 0.1341 AU at apoapsis, driving measurable seasonal insolation cycles.
⚠️ Thermal Regime (Irradiated / Hot Zone): At an equilibrium temperature of 498 K (+225°C / +437°F) and receiving 10.20 S⊕ (~13,882 W/m²), HD 73583 c orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star HD 73583 is classified as an orange K-type star of spectral type K4 V with an effective photospheric temperature of 4,511 K, a radius of 0.65 R☉, a mass of 0.73 M☉, an estimated bolometric luminosity of 0.157 L☉. Stellar evolution modeling indicates an estimated stellar age of 0.48 Gyr and a metallicity of [Fe/H] = 0 dex (near-solar heavy-element abundance). From Earth, HD 73583 shines at apparent V-band magnitude 9.67 (accessible to binoculars and small amateur telescopes) in the Southern celestial hemisphere. The HD 73583 system is a multi-planet architecture hosting 2 confirmed worlds, with HD 73583 c sharing its stellar neighborhood alongside HD 73583 b.
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 73583 |
| Spectral Type | K4 V |
| Effective Temp (Teff) | 4,511 K |
| Stellar Radius | 0.6500 R☉ |
| Stellar Mass | 0.7300 M☉ |
| Bolometric Luminosity | 0.157 L☉ |
| Metallicity [Fe/H] | 0.000 dex |
| Stellar Age | 0.480 Gyr |
| Apparent Magnitude | V: 9.670 · G: 9.270 |
| System Architecture | 1 Star, 2 Planets |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.124200 AU |
| Orbital Period | 18.88 days |
| Mean Orbital Velocity | 71.6 km/s |
| Orbital Eccentricity (e) | 0.08000 |
| Orbital Inclination (i) | 89.7200° |
| Mean Bulk Density | 3.92 g/cm³ (22.5 km/s vesc) |
| Insolation Flux | 10.2000 S⊕ (~13,882 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 103.000 LY (31.567 pc) |