Messier 47 (NGC 2422)
Coordinates, Gaia DR3 distance (475 pc), magnitude 4.2, Messier sign-error history, and observing guide for Messier 47 in Puppis.
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 |
|---|---|---|---|---|---|
| Integrated visual magnitude (V) | 4.2 mag | ± 0.1 mag | Wide-aperture integrated photometry | definitive | Revised New General Catalogue and Index Catalogue (RNGC/IC) |
| Heliocentric distance | 1550 ly | ± 20 ly | Gaia DR3 astrometric parallax of ~500 members (475 ± 6 pc) (J2016.0) | definitive | ESA Gaia Archive — Data Release 3 |
| Apparent diameter | 30 arcmin | ± 2.5 arcmin | Visual and Gaia DR3 member core extent | high-confidence | Revised New General Catalogue and Index Catalogue (RNGC/IC) |
| Main-sequence turnoff & white-dwarf age | 0.08 Gyr | ± 0.015 Gyr | Gaia DR3 B-star turnoff & massive white-dwarf cooling | high-confidence | ESA Gaia Archive — Data Release 3 |
J2000 Equatorial Sky Chart & Culmination Altitude
The chart below plots Messier 47 (NGC 2422 Puppis Open Cluster) at RA 07h 36m 35.00s, Dec -14° 29′ 00.0″ within Puppis, 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
Messier 47 (NGC 2422) is a bold, sparkling naked-eye open cluster located 1,550 light-years (475 ± 6 parsecs) away in northern Puppis. First recorded by Giovanni Battista Hodierna before 1654, M47 became one of the famous 'missing Messier objects' for nearly 190 years after Charles Messier observed it on February 19, 1771, but made a sign error when computing its right ascension offset from the reference star 2 Navis (2 Puppis). William Herschel independently recataloged the real cluster as H VIII.38 (NGC 2422) in 1785, and Canadian astronomer T. F. Morris finally proved in 1959 that Messier's M47 and NGC 2422 were one and the same.
Spanning 30 arcminutes on the sky (~12 light-years physically), M47 is only ~80 million years old and resembles a slightly more compact, distant cousin of the Pleiades. Its ~500 confirmed members are led by brilliant blue-white B2 to B9 main-sequence stars—including the 5.7-magnitude Be star HD 60855—contrasting with two luminous orange K-type red giants (magnitudes 5.7 and 7.8).
Even though M47 and M46 sit only 1.3 degrees apart on the sky and share similar 30-arcminute apparent diameters, M46 is more than three times farther away and three times older, making the pair a premier demonstration of cosmic perspective.
Practical Visual Observing Guide
- Located 12° east and 2° north of Sirius (α Canis Majoris), and 1.3° west-northwest of M46.
- Easily visible to the naked eye at magnitude 4.2 under dark skies, and resolves in 7×50 binoculars into a dozen coarse 5th-to-8th magnitude stars next to the misty glow of M46.
- In a 70–130 mm telescope at 25×–50×, look near the cluster center for the neat equal-brightness double star Struve 1121 (Σ 1121, two magnitude 7.9 B-type stars separated by 7.4″) and the warm orange giant HD 60986.
Catalog Cross-Identifications & Aliases
Common Aliases: M47 · NGC 2422
| Catalog Authority | Identifier |
|---|---|
| MESSIER | M 47 |
| NGC | NGC 2422 |
| SIMBAD | M 47 |
| WIKIDATA | Q11415 |
Related Objects, Comparisons & Guides
Messier 46 (NGC 2437 & NGC 2438 Planetary Pair)
Coordinates, Gaia DR3 distance (1.51 kpc), magnitude 6.1, superposed planetary nebula NGC 2438, and observing guide for M46 in Puppis.
Little Beehive Cluster (Messier 41 / NGC 2287)
Coordinates, Gaia DR3 distance (716 pc), magnitude 4.5, central K3 II orange giant HD 49091, and Sirius finder guide for M41 in Canis Major.
Messier 48 (NGC 2548 Hydra Open Cluster)
Coordinates, Gaia DR3 distance (762 pc), magnitude 5.5, lost Messier declination recovery, and observing guide for M48 in Hydra.
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.
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
- 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