W Virginis (HD 116802)
Coordinates, Gaia DR3 distance (~1.84 kpc), 17.27-day pulsation period, Baade's 1952 doubling of the universe scale, and guide for W Virginis.
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 |
|---|---|---|---|---|---|
| Visual magnitude range (V) | 10.1 mag | ± 0.65 mag | Photoelectric & CCD light curve (varies from V = 9.46 at peak to 10.75 at minimum) | definitive | SIMBAD Astronomical Database (CDS) |
| Radial pulsation period | 17.2736 d | ± 0.005 d | AAVSO & GCVS visual/CCD phase tracking (exhibits cycle-to-cycle shock jitter) | definitive | SIMBAD Astronomical Database (CDS) |
| Heliocentric distance (Gaia DR3 + Period-Luminosity) | 1840 pc | ± 110 pc | Gaia DR3 parallax (0.54 ± 0.03 mas / ~6,000 ly) & Type II Cepheid K-band PL relation (J2016.0) | high-confidence | ESA Gaia Archive — Data Release 3 |
| Mean bolometric luminosity | 830 L☉ | ± 80 L☉ | Type II Cepheid calibration (~1.5 mag / 4× fainter than a 17-day Classical Cepheid!) | high-confidence | SIMBAD Astronomical Database (CDS) |
| Metallicity [Fe/H] | -1 dex | ± 0.1 dex | High-resolution Population II spectroscopy | definitive | SIMBAD Astronomical Database (CDS) |
J2000 Equatorial Sky Chart & Culmination Altitude
The chart below plots W Virginis (Type II Cepheid Prototype) at RA 13h 26m 01.99s, Dec -03° 22′ 43.1″ 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
W Virginis (HD 116802), discovered in 1866 by German astronomer Eduard Schönfeld in southern Virgo ~8° north of Spica, is one of the most historically pivotal variable stars in cosmology. For four decades after Henrietta Swan Leavitt discovered the Cepheid Period–Luminosity law, astronomers assumed all Cepheids with the same pulsation period had the same intrinsic luminosity, calibrating the zero point using nearby old globular-cluster Cepheids while observing young spiral-arm Cepheids in the Andromeda Galaxy (M31).
In 1952 at the International Astronomical Union assembly in Rome, Walter Baade used observations from the new 200-inch Hale Telescope at Palomar to announce that Cepheids actually belong to two distinct stellar populations: young, massive (~5–10 solar-mass) Population I 'Classical Cepheids' (like Delta Cephei) and old, low-mass (~0.5–0.6 solar-mass), metal-poor Population II 'W Virginis stars' (Type II Cepheids). Because a 17.27-day Classical Cepheid is four times more luminous (1.5 magnitudes brighter) than 17.27-day W Virginis, Baade's discovery instantly doubled the measured distance to Andromeda and doubled the age and scale of the entire observable universe!
Located ~1.84 kiloparsecs (~6,000 light-years) high above the Galactic plane, W Virginis is an old asymptotic-giant-branch halo star executing a thermal-pulse blue loop across the instability strip. Every 17.2736 days it varies between magnitude 9.46 and 10.75 as strong hypersonic shock waves propagate outward through its low-density atmosphere, splitting its hydrogen emission lines.
Practical Visual Observing Guide
- Located in Virgo about 7.8° north of Spica (α Virginis) and 4.5° southeast of Porrima (γ Virginis).
- Varying between visual magnitude 9.46 and 10.75 over its 17.3-day cycle, W Virginis is an accessible and rewarding target for an 80–150 mm (3–6 inch) telescope at 60×–120× using an AAVSO variable-star chart.
Catalog Cross-Identifications & Aliases
Common Aliases: HD 116802 · HIP 65531 · BD-02 3683
| Catalog Authority | Identifier |
|---|---|
| GAIADR3 | 3637024467387100160 |
| HIP | HIP 65531 |
| HD | HD 116802 |
| SIMBAD | V* W Vir |
| WIKIDATA | Q2538005 |
Related Objects, Comparisons & Guides
Delta Cephei (Cepheid Distance Ladder Anchor)
Coordinates, Gaia/HST distance (290 pc), 5.366-day pulsation period, Leavitt law calibration, and observing guide for Delta Cephei.
RR Lyrae (Horizontal-Branch Standard Candle)
Coordinates, Gaia DR3 distance (264 pc), 13.60-hour pulsation cycle, Blazhko effect, and cosmic distance ladder guide for RR Lyrae.
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.
Apparent vs Absolute Magnitude Explained
Understand the logarithmic Pogson astronomical magnitude scale, apparent visual magnitude (m), absolute magnitude (M at 10 parsecs), and bolometric corrections.
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
- ESA Gaia Archive — Data Release 3 (DR3 (2022-06-13)): Gaia Collaboration, Vallenari, A., et al. 2023, A&A, 674, A1 (Gaia Data Release 3) — European Space Agency / Gaia DPAC
- 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