Porrima (Gamma Virginis / γ¹ & γ² Virginis)
Coordinates, Hipparcos distance (38.1 ly), 169-year eccentric F0V+F0V visual binary orbit (3.4″ in 2026), and observing guide for Porrima.
Provenance-Backed Scientific Measurements
Every measurement below preserves its unit, uncertainty interval, observational method, reference epoch, quality status, and primary catalog source. See Uncertainty & Provenance for how competing measurements are handled.
| Parameter | Value | Uncertainty | Method & Epoch | Quality Status | Source Archive |
|---|---|---|---|---|---|
| Combined apparent visual magnitude (V) | 2.74 mag | ± 0.01 mag | Johnson UBV photometry (γ Vir A = 3.48 mag, γ Vir B = 3.50 mag) | definitive | Hipparcos New Reduction Catalog |
| Trigonometric parallax | 85.58 mas | ± 0.6 mas | Hipparcos New Reduction + dynamical binary orbit (11.68 ± 0.08 pc / 38.1 ly) (J2000.0) | definitive | Hipparcos New Reduction Catalog |
| Visual binary orbital period | 61705 d | ± 75 d | Three-century visual & speckle astrometric orbit (168.93 ± 0.20 yr, e = 0.8825) | definitive | SIMBAD Astronomical Database (CDS) |
| Component stellar mass (γ Vir A & B each) | 1.4 M☉ | ± 0.04 M☉ | 3D astrometric + radial-velocity Keplerian orbit (A = 1.40 M☉, B = 1.39 M☉) | definitive | SIMBAD Astronomical Database (CDS) |
| Visual angular separation (2026 epoch) | 0.057 arcmin | ± 0.002 arcmin | Orbital ephemeris (~3.4 arcseconds in 2026, widening from 0.36″ in 2005 toward 6.0″ in 2090) | definitive | SIMBAD Astronomical Database (CDS) |
J2000 Equatorial Sky Chart & Culmination Altitude
The chart below plots Porrima (Gamma Virginis Twin F0V Binary) at RA 12h 41m 39.64s, Dec -01° 26′ 57.8″ within Virgo, alongside peak meridian transit altitudes for 40°N and 30°S observers. Use the RA/Dec Coordinate Converter to compute exact culmination altitude for your latitude.
Astrophysical Context & Structure
Porrima (Gamma Virginis, named after the Roman goddess of prophecy) is the second-brightest star in Virgo at combined apparent magnitude 2.74, located just 11.68 ± 0.08 parsecs (38.1 light-years) from Earth and 1.4° north of the celestial equator. First resolved by Father Jean Richaud at Pondicherry, India, in 1689 and measured by James Bradley in 1718, Porrima is one of the most dynamic visual binaries accessible to amateur telescopes.
The system consists of two virtually identical twin F0 V yellow-white main-sequence stars: Gamma Virginis A (magnitude 3.48, 1.40 solar masses, 1.45 solar radii, 7,100 K) and Gamma Virginis B (magnitude 3.50, 1.39 solar masses, 1.43 solar radii). Orbiting their common center of mass every 168.93 years along a highly eccentric ellipse (eccentricity e = 0.8825), their true physical separation varies from 81 AU at apastron down to just 5.1 AU (Jupiter's distance from the Sun) at periastron.
When Porrima swept through periastron in May 2005 (repeating the 1836 close passage predicted by Sir John Herschel), its angular separation shrank to 0.36 arcseconds, rendering it a single elongated star in all but the largest professional apertures. Since 2005 the twins have rapidly separated, passing 2.0 arcseconds in 2013 and reaching ~3.4 arcseconds in 2026 on their way toward their 6.0-arcsecond maximum around 2090.
Practical Visual Observing Guide
- Located 15° northwest of Spica along the body of Virgo, Porrima is also the primary naked-eye landmark for hopping 4° southeast to the quasar 3C 273 or 8° north into the southern edge of the Virgo Galaxy Cluster.
- In 2026 at ~3.4 arcseconds separation (position angle ~355°), any 60–80 mm telescope at 100×–150× splits Porrima cleanly into two identical, matched 3.5-magnitude creamy-white headlights.
Catalog Cross-Identifications & Aliases
Common Aliases: γ Virginis · Arich · HD 110379 / HD 110380 · HIP 61941 · 29 Virginis
| Catalog Authority | Identifier |
|---|---|
| HIP | HIP 61941 |
| HD | HD 110379 |
| SIMBAD | * gam Vir |
| WIKIDATA | Q13063 |
Related Objects, Comparisons & Guides
Spica (Alpha Virginis Ellipsoidal Binary)
Coordinates, Hipparcos distance (250 ly), 4.01-day close B-star binary, precession discovery history, and observing guide for Spica.
3C 273 (Brightest Quasar in Virgo)
Coordinates, redshift z = 0.1583 (~2.4 billion ly), magnitude 12.85, supermassive black hole accretion, and observing guide for quasar 3C 273.
Castor (Alpha Geminorum Sextuple System)
Coordinates, Hipparcos distance (50.8 ly), 5.6″ A–B binary orbit, YY Geminorum eclipsing pair, and observing guide for Castor.
Angular Size, Separation & Field of View
How angular diameter (degrees, arcminutes, arcseconds), spherical angular separation, and small-angle physical diameter relate to telescope field of view.
Trigonometric Parallax, Parsecs & Gaia DR3
How trigonometric parallax (d_pc = 1 / p_arcsec), the distance modulus equation, Hipparcos, and Gaia DR3 microarcsecond astrometry measure cosmic distances.
Scientific Sources & Dataset Provenance
- Hipparcos New Reduction Catalog (2007 New Reduction): van Leeuwen, F. 2007, A&A, 474, 653 (Validation of the new Hipparcos reduction) — ESA / van Leeuwen (2007)
- SIMBAD Astronomical Database (CDS) (2026-10 release): Wenger, M., et al. 2000, A&AS, 143, 9 (The SIMBAD astronomical database) — Centre de Données astronomiques de Strasbourg