V404 Cygni
Reference data for V404 Cygni: 9.0 solar mass black hole, VLBI parallax distance of 7,800 ly, 6.47-day orbit, and 2015 X-ray dust-ring outburst.
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 |
|---|---|---|---|---|---|
| Distance | 7800 ly | ± 460 ly | First geometric VLBI radio parallax for a black hole system: 0.418 ± 0.024 mas (Miller-Jones et al. 2009). | definitive | SIMBAD Astronomical Database (CDS) |
| Quiescent Magnitude (V) | 18.4 mag | ± 0.2 mag | Brightens to V ~ 11.5 during dramatic X-ray nova outbursts. | definitive | SIMBAD Astronomical Database (CDS) |
| Binary Orbital Period | 6.4714 d | ± 0.0001 d | Coherent X-ray/radio timing or binary radial-velocity solution | definitive | SIMBAD Astronomical Database (CDS) |
| Black Hole Mass | 9 M☉ | ± 0.6 M☉ | Dynamical mass function f(M) = 6.08 ± 0.06 M☉ combined with 67° orbital inclination. | definitive | SIMBAD Astronomical Database (CDS) |
| Proper Motion (RA) | -5.04 mas/yr | ± 0.08 mas/yr | Multi-epoch VLBI or Gaia DR3 astrometry | definitive | ESA Gaia Archive — Data Release 3 |
| Proper Motion (Dec) | -7.64 mas/yr | ± 0.09 mas/yr | Multi-epoch VLBI or Gaia DR3 astrometry | definitive | ESA Gaia Archive — Data Release 3 |
J2000 Equatorial Sky Chart & Culmination Altitude
The chart below plots V404 Cygni (GS 2023+338) — Black Hole Binary at RA 20h 24m 03.83s, Dec +33° 52′ 01.9″ 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
First recorded on photographic plates as Nova Cygni 1938 when it flared to 12th magnitude, V404 Cygni erupted again in May 1989 and was pinpointed by the Japanese Ginga X-ray satellite as transient source GS 2023+338. Once the outburst faded to quiescence (V ~ 18.4), Jorge Casares, Philip Charles, and Tim Naylor measured the radial velocity curve of its K0IV subgiant companion star across its 6.4714-day orbit, finding a mass function of 6.08 ± 0.06 solar masses—the highest and most ironclad dynamical proof of a stellar-mass black hole known at the time.
After 26 years of slumber, V404 Cygni reawakened in June 2015, briefly becoming up to fifty times brighter than the Crab Nebula in hard X-rays and flickering wildly by several magnitudes over minutes in optical light. High-speed VLBA radio imaging caught discrete plasma clouds shooting out in rapidly wobbling relativistic jets driven by Lense-Thirring frame-dragging of its puffed-up inner accretion disk. As the intense X-ray flashes propagated toward Earth, they scattered off intervening sheets of interstellar dust between 4,000 and 7,000 light-years away, creating spectacular expanding concentric X-ray light-echo rings imaged by Swift and Chandra.
In 2009, V404 Cygni became the first black hole system with a direct geometric parallax distance (7,800 ± 460 light-years) measured via radio interferometry. In 2024, Gaia astrometry revealed an unexpected outer third star bound to the system at a separation of roughly 3,500 astronomical units—implying that the central 9-solar-mass black hole formed via direct collapse without receiving a strong natal supernova kick that would have unbound the fragile outer companion.
Practical Visual Observing Guide
- In quiescence, V404 Cygni sits near V = 18.4 in Cygnus, requiring 12-inch+ CCD imaging to monitor.
- During its rare multi-decade outbursts (1938, 1956, 1989, 2015), it surges to V ~ 11.5 and exhibits rapid optical flares of 1–2 magnitudes on timescales of minutes, easily tracked by amateur AAVSO observers.
- Located in central Cygnus roughly 4 degrees south of Sadr (Gamma Cygni).
Catalog Cross-Identifications & Aliases
Common Aliases: GS 2023+338 · Nova Cygni 1938 · Nova Cygni 1989
| Catalog Authority | Identifier |
|---|---|
| SIMBAD | GS 2023+338 |
Related Objects, Comparisons & Guides
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.
SS 433 (V1343 Aquilae) — Galactic Microquasar
Reference data for SS 433: 0.26c relativistic precessing jets, 13.08-day eclipsing binary orbit in Aquila, and the W50 Manatee Nebula.
Hercules X-1 (HZ Herculis) — X-Ray Pulsar
Reference data for Hercules X-1: 1.24-second X-ray pulsar spin, 1.70-day binary orbit, 35-day warped disk cycle, and cyclotron magnetic field.
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.
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.
Scientific Sources & Dataset Provenance
- 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
- 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