Messier 48 (NGC 2548)
Coordinates, Gaia DR3 distance (762 pc), magnitude 5.5, lost Messier declination recovery, and observing guide for M48 in Hydra.
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) | 5.5 mag | ± 0.1 mag | Wide-aperture integrated photometry | definitive | Revised New General Catalogue and Index Catalogue (RNGC/IC) |
| Heliocentric distance | 2485 ly | ± 35 ly | Gaia DR3 astrometric parallax of ~450 members (762 ± 11 pc) (J2016.0) | definitive | ESA Gaia Archive — Data Release 3 |
| Apparent diameter | 54 arcmin | ± 4 arcmin | Wide-field member star counts | high-confidence | Revised New General Catalogue and Index Catalogue (RNGC/IC) |
| Main-sequence turnoff & gyrochronology age | 0.42 Gyr | ± 0.04 Gyr | Gaia DR3 isochrone + solar-type stellar rotation periods | high-confidence | ESA Gaia Archive — Data Release 3 |
J2000 Equatorial Sky Chart & Culmination Altitude
The chart below plots Messier 48 (NGC 2548 Hydra Open Cluster) at RA 08h 13m 43.00s, Dec -05° 45′ 00.0″ within Hydra, 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 48 (NGC 2548) is a large, triangular naked-eye open cluster located 2,485 light-years (762 ± 11 parsecs) away on the extreme western border of Hydra near Monoceros. Like M47, which Charles Messier logged on the very same night of February 19, 1771, M48 was considered 'lost' for nearly two centuries because Messier accidentally recorded its declination 5 degrees too far north (−1°16′ instead of −5°45′). Caroline Herschel independently rediscovered the cluster in March 1783, and T. F. Morris and Oswald Thomas proved in the 1930s–1950s that Messier's 5-degree arithmetic slip pointed directly to NGC 2548.
Spanning 54 arcminutes across the sky—nearly twice the diameter of the full Moon—and about 36 light-years in physical width, M48 contains ~450 confirmed stars with an age of ~420 million years. Its main sequence turns off around spectral type A2 V (magnitude 8.8), accompanied by three evolved yellow-orange G/K giant stars shining between magnitudes 8.2 and 9.1.
Because M48 sits 15 degrees above the Galactic plane in a transparent, dust-free window, astronomers use its F- and G-type dwarfs as a standard benchmark for calibrating lithium depletion and magnetic braking in intermediate-age stars.
Practical Visual Observing Guide
- Located in a sparse region of western Hydra, about 14° southeast of Procyon (α Canis Minoris) and 3.5° southeast of Zeta Monocerotis.
- Under dark skies M48 is clearly visible to the naked eye at magnitude 5.5 as a grainy patch larger than the full Moon.
- In 10×50 binoculars or a rich-field telescope at 15×–35×, a bright north-south spine of 8th- and 9th-magnitude white and golden stars cuts through a heart- or chevron-shaped halo of ~80 stars.
Catalog Cross-Identifications & Aliases
Common Aliases: M48 · NGC 2548
| Catalog Authority | Identifier |
|---|---|
| MESSIER | M 48 |
| NGC | NGC 2548 |
| SIMBAD | M 48 |
| WIKIDATA | Q11417 |
Related Objects, Comparisons & Guides
Messier 47 (NGC 2422 Puppis Open Cluster)
Coordinates, Gaia DR3 distance (475 pc), magnitude 4.2, Messier sign-error history, and observing guide for Messier 47 in Puppis.
Heart-Shaped Cluster (Messier 50 / NGC 2323)
Coordinates, Gaia DR3 distance (961 pc), magnitude 5.9, crimson giant HD 52938 contrast, and observing guide for Messier 50 in Monoceros.
Beehive Cluster (Messier 44 Praesepe)
Coordinates, Gaia DR3 distance (186.2 pc), magnitude 3.1, exoplanet hosts, and observing guide for the Beehive Cluster (M44 / NGC 2632).
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.
Angular Size, Separation & Field of View
How angular diameter (degrees, arcminutes, arcseconds), spherical angular separation, and small-angle physical diameter relate to telescope field of view.
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