P Cygni (34 Cygni / Nova Cygni 1600)
Coordinates, Gaia DR3 distance (1.64 kpc), magnitude 4.82, 610,000 L☉ hypergiant luminosity, P Cygni wind line profile, and guide for P Cygni.
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 |
|---|---|---|---|---|---|
| Current visual magnitude (V) | 4.82 mag | ± 0.08 mag | AAVSO V-band monitoring (erupted to mag 3.0 in 1600; faded below 6.0 in 1626; slowly brightening at +0.15 mag/century) | definitive | Hipparcos New Reduction Catalog |
| Trigonometric distance (Gaia DR3) | 1640 pc | ± 90 pc | Gaia DR3 astrometric parallax (0.610 ± 0.033 mas / 5,350 ± 290 ly) (J2016.0) | definitive | ESA Gaia Archive — Data Release 3 |
| Bolometric luminosity | 610000 L☉ | ± 75000 L☉ | Non-LTE B1 Ia+ wind model (Najarro et al. 1997 / Clark et al. 2012) at ~1.64–1.7 kpc | high-confidence | SIMBAD Astronomical Database (CDS) |
| Photospheric radius | 76 R☉ | ± 8 R☉ | CHARA H-band interferometry & non-LTE wind modeling | high-confidence | SIMBAD Astronomical Database (CDS) |
| Effective temperature | 18700 K | ± 500 K | Quantitative UV/optical/IR wind spectroscopy | definitive | SIMBAD Astronomical Database (CDS) |
J2000 Equatorial Sky Chart & Culmination Altitude
The chart below plots P Cygni (34 Cygni Luminous Blue Variable) at RA 20h 17m 47.20s, Dec +38° 01′ 58.6″ within Cygnus, 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
P Cygni (34 Cygni), located 1.64 ± 0.09 kiloparsecs (5,350 light-years) away near the heart of the Northern Cross in Cygnus, is one of the closest and brightest Luminous Blue Variable (LBV) hypergiants in the Milky Way. On August 18, 1600, Dutch globe maker and cartographer Willem Janszoon Blaeu noticed a 'new' 3rd-magnitude star in Cygnus where none had been charted before; Johann Bayer assigned it the letter 'P' in his 1603 Uranometria. After shining at 3rd magnitude for six years, P Cygni faded below naked-eye visibility by 1626, flared again to magnitude 3.5 in 1655–1659, and since 1715 has settled around magnitude 4.8 while slowly brightening by ~0.15 magnitudes per century as its core evolves.
Radiating an astounding 610,000 times the bolometric luminosity of the Sun from an 18,700 K, 76-solar-radius photosphere (~30–50 solar masses), P Cygni teeters right on the Eddington limit where outward radiation pressure nearly balances inward gravity. Its 1600 and 1655 'Great Eruptions' were non-terminal LBV outbursts closely analogous to Eta Carinae's 1843 eruption, leaving behind two concentric shells of ionized gas spanning 22 arcseconds and 1.6 arcminutes across.
In spectroscopy across all of astrophysics, P Cygni gives its name to the universal 'P Cygni line profile': a strong emission peak flanked on its short-wavelength (blue) side by a deep blueshifted absorption trough, produced whenever an expanding spherical envelope of gas (in OB winds, novae, supernovae, or quasars) moves outward at hundreds of kilometers per second (185 km/s in P Cygni's case).
Practical Visual Observing Guide
- Very easy to locate in Cygnus: look just 1.9° south-southwest of Sadr (Gamma Cygni, the central crossroads star of the Northern Cross) along the neck toward Eta Cygni.
- At apparent visual magnitude 4.82, P Cygni is visible to the naked eye under dark skies and shines in binoculars with a slightly warm golden-white tint (reddened by 1.8 magnitudes of Cygnus Rift interstellar dust) despite its 18,700 K true surface temperature!
Catalog Cross-Identifications & Aliases
Common Aliases: 34 Cygni · Nova Cygni 1600 · HD 193237 · HIP 100044
| Catalog Authority | Identifier |
|---|---|
| GAIADR3 | 2061252976546050688 |
| HIP | HIP 100044 |
| HD | HD 193237 |
| SIMBAD | * 34 Cyg |
| WIKIDATA | Q13067 |
Related Objects, Comparisons & Guides
Eta Carinae (Luminous Blue Variable Binary)
Coordinates, Gaia/expansion distance (2.35 kpc), 5 million L☉ luminosity, 1843 Great Eruption Homunculus, and observing guide for Eta Carinae.
Cygnus X-1 (HDE 226868 X-Ray Black Hole)
Coordinates, VLBA/Gaia distance (2.22 kpc), 21.2-M☉ stellar black hole mass, 5.60-day O-supergiant binary, and observing guide for Cygnus X-1.
Albireo (Beta Cygni Color Double Star)
Coordinates, Gaia DR3 parallaxes of Beta Cygni A & B, 34.6″ angular separation, color contrast, and observing guide for Albireo in Cygnus.
Proper Motion, Radial Velocity & Redshift
How astronomers combine tangential proper motion (mas/yr), Doppler radial velocity (km/s), and cosmological redshift (z) to reconstruct 3D space motion.
Stellar Spectral Classification (OBAFGKM)
Reference guide to Morgan-Keenan (MK) stellar classification (O B A F G K M), luminosity classes (I–V, WD), color index (B-V), and the H-R diagram.
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
- 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