61 Vir b
Astrophysical Synthesis & Habitability Characterization
61 Vir b is a confirmed sub-neptune exoplanet orbiting the star 61 Vir, located approximately 27.7 light-years (8.5 parsecs) from the Solar System. First announced in 2009 by Multiple Observatories using the Radial Velocity detection technique (measuring periodic Doppler reflex motion in the host star's spectrum), this world measures 2.11 Earth radii and has a measured mass of 5.1 Earth masses. Combining its mass and radius yields a mean bulk density of 2.99 g/cm³ (an intermediate density indicative of a deep water-ice mantle or dense volatile envelope), a surface gravity of 1.15 g⊕ (11.28 m/s²), and an escape velocity of 17.4 km/s.
In its orbital architecture around 61 Vir, 61 Vir b completes one full revolution every 4.215 Earth days at a semi-major axis of 0.050201 AU (orbiting interior to Mercury's 0.387 AU benchmark in the Solar System). Its mean orbital velocity is approximately 129.6 km/s (compared to Earth's 29.8 km/s). Its moderate orbital eccentricity of e = 0.12 carries the world between 0.0442 AU at periapsis and 0.0562 AU at apoapsis, driving measurable seasonal insolation cycles.
⚠️ Thermal Regime (Irradiated / Hot Zone): At an equilibrium temperature of 1178 K (+905°C / +1661°F) and receiving 318.84 S⊕ (~433,944 W/m²), 61 Vir b orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star 61 Vir is classified as a solar-type yellow star of spectral type G5 V with an effective photospheric temperature of 5,577 K, a radius of 0.963 R☉, a mass of 0.942 M☉, an estimated bolometric luminosity of 0.805 L☉. Stellar evolution modeling indicates an estimated stellar age of 8.96 Gyr and a metallicity of [Fe/H] = -0.01 dex (near-solar heavy-element abundance). From Earth, 61 Vir shines at apparent V-band magnitude 4.696 (visible to the unaided human eye under dark skies) in the Southern celestial hemisphere. The 61 Vir system is a multi-planet architecture hosting 3 confirmed worlds, with 61 Vir b sharing its stellar neighborhood alongside 61 Vir c, 61 Vir d.
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: Multiple Observatories · Catalogue Source: NASA Exoplanet Archive (IPAC / Caltech).
☀️ Host Star Telemetry
| Host Star Name | 61 Vir |
| Spectral Type | G5 V |
| Effective Temp (Teff) | 5,577 K |
| Stellar Radius | 0.9630 R☉ |
| Stellar Mass | 0.9420 M☉ |
| Bolometric Luminosity | 0.805 L☉ |
| Metallicity [Fe/H] | -0.010 dex |
| Stellar Age | 8.960 Gyr |
| Apparent Magnitude | V: 4.696 · G: 4.541 |
| System Architecture | 1 Star, 3 Planets |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.050201 AU |
| Orbital Period | 4.215 days |
| Mean Orbital Velocity | 129.6 km/s |
| Orbital Eccentricity (e) | 0.12000 |
| Orbital Inclination (i) | — |
| Mean Bulk Density | 2.99 g/cm³ (17.4 km/s vesc) |
| Insolation Flux | 318.8418 S⊕ (~433,944 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 27.700 LY (8.503 pc) |