61 Vir d
Astrophysical Synthesis & Habitability Characterization
61 Vir d 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 5.11 Earth radii (0.46 Jupiter radii) and has a measured mass of 22.9 Earth masses. Combining its mass and radius yields a mean bulk density of 0.95 g/cm³ (a low bulk density dominated by an extended hydrogen-helium gaseous envelope), a surface gravity of 0.88 g⊕ (8.63 m/s²), and an escape velocity of 23.7 km/s.
In its orbital architecture around 61 Vir, 61 Vir d completes one full revolution every 123.01 Earth days at a semi-major axis of 0.476 AU (situated at an orbital separation between Mercury's 0.39 AU and Venus's 0.72 AU). Its mean orbital velocity is approximately 42.1 km/s (compared to Earth's 29.8 km/s). The planet follows a highly eccentric trajectory (e = 0.35, swinging from 0.3094 AU at periapsis out to 0.6426 AU at apoapsis), pointing to past dynamical scattering or secular gravitational perturbations.
⚠️ Thermal Regime (Irradiated / Hot Zone): At an equilibrium temperature of 383 K (+110°C / +230°F) and receiving 3.55 S⊕ (~4,827 W/m²), 61 Vir d 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 d sharing its stellar neighborhood alongside 61 Vir b, 61 Vir 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: 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) | 0.476000 AU |
| Orbital Period | 123.01 days |
| Mean Orbital Velocity | 42.1 km/s |
| Orbital Eccentricity (e) | 0.35000 |
| Orbital Inclination (i) | — |
| Mean Bulk Density | 0.95 g/cm³ (23.7 km/s vesc) |
| Insolation Flux | 3.5464 S⊕ (~4,827 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 27.700 LY (8.503 pc) |