Messier 3 (NGC 5272)
Coordinates, Gaia DR3 distance (10.18 kpc), magnitude 6.19, RR Lyrae variable benchmark data, and observing guide for Messier 3 in Canes Venatici.
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) | 6.19 mag | ± 0.04 mag | Integrated photoelectric & CCD photometry | definitive | Catalog of Parameters for Milky Way Globular Clusters |
| Heliocentric distance | 33200 ly | ± 400 ly | Gaia EDR3 parallax + RR Lyrae P-L relation (10.18 ± 0.12 kpc) (J2016.0) | definitive | ESA Gaia Archive — Data Release 3 |
| Apparent diameter | 18 arcmin | ± 1.5 arcmin | Deep tidal halo star counts | high-confidence | Revised New General Catalogue and Index Catalogue (RNGC/IC) |
| Isochrone turnoff age | 11.4 Gyr | ± 0.4 Gyr | HST ACS color-magnitude diagram fitting | model-dependent | Catalog of Parameters for Milky Way Globular Clusters |
J2000 Equatorial Sky Chart & Culmination Altitude
The chart below plots Messier 3 (NGC 5272 Globular Cluster) at RA 13h 42m 11.62s, Dec +28° 22′ 38.2″ within Canes Venatici, 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 3 (NGC 5272) is the very first original deep-sky discovery made by Charles Messier on May 3, 1764, prompting him to begin systematically surveying the sky for comet look-alikes. Situated high in the northern Galactic halo at a distance of 33,200 light-years (10.18 ± 0.12 kiloparsecs) in southern Canes Venatici, M3 contains roughly 500,000 stars and a total mass of ~410,000 solar masses within a physical span of 180 light-years.
In stellar astrophysics, M3 is the prototype of Oosterhoff Type I globular clusters, hosting nearly 300 known variable stars—more than any other cluster in the Messier catalog. Over 240 of these variables are RR Lyrae pulsating horizontal-branch stars with mean fundamental periods near 0.55 days, discovered in massive photographic campaigns initiated by Solon Irving Bailey at Harvard Observatory in 1895. Pairing M3 with Hercules cluster M13 also defines the classic 'second parameter problem': despite matching iron abundances ([Fe/H] ≈ −1.50 dex), M3 exhibits a heavily populated RR Lyrae instability strip whereas M13 has an extreme blue horizontal branch.
M3 also harbors an unusually high number of 'blue stragglers'—luminous main-sequence stars hotter and bluer than the 11.4-billion-year turnoff point, rejuvenated by direct stellar collisions in the dense inner core or mass transfer across close binary systems.
Practical Visual Observing Guide
- Located roughly 12° northwest of brilliant orange Arcturus (α Boötis), slightly north of the line connecting Arcturus to Cor Caroli (α Canum Venaticorum).
- At magnitude 6.19 under negligible interstellar extinction (E(B−V) = 0.01 mag), M3 is visible to the naked eye from dark sites and easily spotted in 7×50 binoculars near a 6.3-magnitude field star 30′ southwest.
- A 100–150 mm telescope at 120×–180× resolves both the sparkling outer halo and the bright Class VI core into hundreds of 12.7-magnitude red giants.
Catalog Cross-Identifications & Aliases
Common Aliases: M3 · NGC 5272
| Catalog Authority | Identifier |
|---|---|
| MESSIER | M 3 |
| NGC | NGC 5272 |
| SIMBAD | M 3 |
| WIKIDATA | Q11177 |
Related Objects, Comparisons & Guides
Messier 13 (Hercules Globular Cluster)
Coordinates, Gaia DR3 distance (7.42 kpc), visual magnitude 5.78, and Keystone finder guide for Messier 13 (NGC 6205) in Hercules.
Messier 5 (NGC 5904 Globular Cluster)
Coordinates, Gaia DR3 distance (7.48 kpc), magnitude 5.65, eccentric halo orbit, and observing guide for Messier 5 (NGC 5904) in Serpens Caput.
Messier 53 (NGC 5024 Outer Halo Globular)
Coordinates, Gaia DR3 distance (18.50 kpc), magnitude 7.61, Helmi Stream origin, and observing guide for Messier 53 in Coma Berenices.
Apparent vs Absolute Magnitude Explained
Understand the logarithmic Pogson astronomical magnitude scale, apparent visual magnitude (m), absolute magnitude (M at 10 parsecs), and bolometric corrections.
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
- Catalog of Parameters for Milky Way Globular Clusters (2010 / 2021 Gaia EDR3 revision): Harris, W. E. 1996 (2010 ed.), AJ, 112, 1487; Vasiliev, E. & Baumgardt, H. 2021, MNRAS, 505, 5978 — McMaster University / Gaia EDR3 Cluster Survey
- 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
- 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