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.
Aliases: M13, NGC 6205, Hercules Globular Cluster
Globular Clusters Catalog & Observing Guide
Dense, gravitationally bound spherical systems of 10⁵ to 10⁶ ancient Population II stars orbiting in the Milky Way's Galactic halo and thick disk.
Cataloged Profiles4 Objects
ClassificationGlobular Clusters
Machine-Readable DataJSON Shard (globular-clusters.json)
Physical & Observational Overview
Globular clusters are among the oldest surviving structures in the Milky Way, with main-sequence turnoff ages spanning 11.5 to 13.0 billion years. Roughly 160 globular clusters are cataloged in our galaxy, orbiting along high-inclination halo trajectories at galactocentric distances from a few kiloparsecs out to >100 kpc.
Because all stars in a classic globular cluster formed at nearly the same distance, age, and baseline metallicity, their color-magnitude diagrams provide laboratories for horizontal-branch evolution, RR Lyrae distance calibration, and dynamical core collapse.
Classification Criteria: Classified by Shapley–Sawyer concentration class (I = most concentrated core, XII = least concentrated), iron-to-hydrogen abundance ratio [Fe/H] (typically −2.3 to −0.5 dex), and horizontal-branch morphology.
Visual Observing Regime: Bright globular clusters appear as fuzzy round patches in 7×50 binoculars and resolve into hundreds or thousands of individual red-giant stars in 100–200 mm telescopes at 120×–200× magnification.
Companion Theoretical Reference: Explore globular cluster dynamics and Population II stellar evolution on FastCosmos.us.
Globular Clusters Comparison Table
| Object | Constellation | Classification | RA (J2000) | Dec (J2000) | Min. Instrument | Best Season |
|---|---|---|---|---|---|---|
| Messier 13 (Hercules Globular Cluster) | Hercules | Globular cluster | 16h 41m 41.24s | +36° 27′ 35.5″ | 7×50 binoculars (naked eye under dark skies) | Late Spring to Summer (May–August) |
| Omega Centauri (NGC 5139 Cluster) | Centaurus | Globular cluster / stripped dwarf galaxy nucleus | 13h 26m 47.24s | -47° 28′ 46.1″ | Naked eye (south of 35°N) | Spring to Early Summer (April–June) |
| Messier 92 (NGC 6341 in Hercules) | Hercules | Globular cluster | 17h 17m 07.40s | +43° 08′ 09.4″ | 7×50 binoculars | Late Spring to Summer (May–August) |
| 47 Tucanae (NGC 104 Globular Cluster) | Tucana (Southern Sky) | Globular cluster | 00h 24m 05.30s | -72° 04′ 52.6″ | Naked eye (Southern Hemisphere) | Southern Spring to Summer (September–December) |
Detailed Globular Clusters Profiles
Omega Centauri (NGC 5139 Cluster)
Coordinates, Gaia DR3 distance (5.43 kpc), magnitude 3.68, and multi-population core data for Omega Centauri (NGC 5139) in Centaurus.
Aliases: ω Centauri, NGC 5139, Caldwell 80
Messier 92 (NGC 6341 in Hercules)
Coordinates, Gaia distance (8.50 kpc), metal-poor [Fe/H] = −2.31 dex, and observing guide for ancient globular cluster Messier 92 in Hercules.
Aliases: M92, NGC 6341
47 Tucanae (NGC 104 Globular Cluster)
Coordinates, Gaia distance (4.52 kpc), magnitude 4.09, millisecond pulsar core, and observing guide for 47 Tucanae (NGC 104).
Aliases: 47 Tuc, NGC 104, Caldwell 106
Related Astrometric & Optical Reference Guides
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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.
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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.