Perseus Double Cluster (NGC 869 & NGC 884)
Coordinates, Gaia DR3 distance (2.29 kpc), age 14 Myr, supergiant population, and observing guide for NGC 869 and NGC 884 in Perseus.
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 visual magnitude (V) | 3.7 mag | ± 0.1 mag | Integrated wide-field photometry (NGC 869 = 4.3, NGC 884 = 4.4) | definitive | Revised New General Catalogue and Index Catalogue (RNGC/IC) |
| Heliocentric distance (Perseus Arm) | 2290 pc | ± 70 pc | Gaia DR3 astrometric parallax of OB supergiant members (J2016.0) | high-confidence | ESA Gaia Archive — Data Release 3 |
| Cluster age | 0.014 Gyr | ± 0.002 Gyr | Massive B0–B2 supergiant turnoff & red supergiant isochrones | high-confidence | ESA Gaia Archive — Data Release 3 |
| Combined apparent span | 60 arcmin | ± 5 arcmin | Combined angular extent across both cores | high-confidence | Revised New General Catalogue and Index Catalogue (RNGC/IC) |
J2000 Equatorial Sky Chart & Culmination Altitude
The chart below plots Double Cluster (NGC 869 & NGC 884) at RA 02h 20m 00.00s, Dec +57° 08′ 00.0″ within Perseus, 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
The Perseus Double Cluster—comprising NGC 869 (h Persei) on the west and NGC 884 (χ Persei) on the east—is the showcase twin open cluster of the northern Milky Way. Situated 2.29 ± 0.07 kiloparsecs (7,470 light-years) away inside the Perseus spiral arm, the two clusters form the dense twin nuclei of the Perseus OB1 stellar association and contain a combined mass exceeding 20,000 solar masses.
Although early astronomers occasionally wondered if the two clusters were merely a line-of-sight alignment, Gaia DR3 parallaxes and radial velocities (~−43 km/s) confirm they lie at virtually identical distances, separated physically by only ~25 parsecs (80 light-years). At a remarkably young age of 14 ± 2 million years, both clusters blaze with luminous blue-white B0–B2 supergiants.
NGC 884 is especially celebrated among visual observers and stellar evolution researchers for its population of evolved M-type red supergiants—including RS Persei, AD Persei, and FZ Persei—whose deep ruby-amber hues provide a striking visual contrast against hundreds of hot blue-white stars.
Practical Visual Observing Guide
- Easily located midway between the W of Cassiopeia (specifically Ruchbah and Gamma Cassiopeiae) and Mirfak/Eta Persei.
- Visible to the naked eye as an elongated 1°-wide bright patch in the Milky Way; 10×50 binoculars resolve both cores into twin jewel boxes.
- Through an 80–150 mm telescope at 30×–50× with a wide-angle eyepiece, both NGC 869 and NGC 884 fit in a single 1.2° field of view, showcasing five 8th-magnitude red supergiants scattered around χ Persei.
Catalog Cross-Identifications & Aliases
Common Aliases: NGC 869 · NGC 884 · h and Chi Persei · Caldwell 14
| Catalog Authority | Identifier |
|---|---|
| NGC | NGC 869 / NGC 884 |
| SIMBAD | NGC 869 |
| WIKIDATA | Q14262 |
Related Objects, Comparisons & Guides
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Coordinates, Gaia DR3 distance (186.2 pc), magnitude 3.1, exoplanet hosts, and observing guide for the Beehive Cluster (M44 / NGC 2632).
Betelgeuse (Alpha Orionis Red Supergiant)
Coordinates, competing optical vs radio distances (168 vs 222 pc), radius, Great Dimming physics, and observing guide for Betelgeuse.
Autumn Sky Tour: Andromeda, Perseus & Cassiopeia
Autumn observing guide from Cassiopeia and Perseus (Double Cluster, Algol, Cas A) across Andromeda and Triangulum to Local Group galaxies M31 and M33.
Binocular Deep-Sky Objects Observing Guide
How to observe open clusters, globular clusters, diffuse nebulae, and Local Group galaxies with 7x50, 10x50, and 15x70 astronomy binoculars.
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.
Astronomical Catalogs Explained (M, NGC, Gaia)
How astronomical designations work across the Messier (M), NGC/IC, Bayer/Flamsteed, Henry Draper (HD), Hipparcos (HIP), and Gaia DR3 catalogs.
NGC & Caldwell Deep-Sky Cross-Walk Catalog
Cross-reference guide to Dreyer's New General Catalogue (NGC) showpieces, including southern gems Omega Centauri, 47 Tucanae, Carina Nebula, and the Veil.
Galactic Open Clusters Reference Catalog
Cross-reference catalog of nearby galactic disk open star clusters—Hyades, Pleiades (M45), Beehive (M44), and Double Cluster (NGC 869/884)—with Gaia DR3 data.
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
- Revised New General Catalogue and Index Catalogue (RNGC/IC) (2024/2026 edition): Steinicke, W. 2010, Observing and Cataloguing Nebulae and Star Clusters (Cambridge Univ. Press); Verga, M. OpenNGC (CC-BY-SA 4.0 / data tables) — Wolfgang Steinicke / OpenNGC
- 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