Messier 13 vs Messier 92 Hercules Globulars
Compare the twin Hercules globular clusters Messier 13 (NGC 6205) and Messier 92 (NGC 6341) in age, metallicity, core concentration, and eyepiece resolution.
Compared Celestial Objects
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.
Constellation: Hercules · Coords: 16h 41m 41.24s, +36° 27′ 35.5″
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.
Constellation: Hercules · Coords: 17h 17m 07.40s, +43° 08′ 09.4″
Normalized Shared Parameter Table
| Parameter | Unit / Scale | Messier 13 (Hercules Globular Cluster) | Messier 92 (NGC 6341 in Hercules) |
|---|---|---|---|
| Integrated Visual Magnitude (V) | mag | +5.78 ± 0.05 | +6.42 ± 0.05 |
| Heliocentric Distance | kpc | 7.42 ± 0.08 kpc (24,200 ly) | 8.50 ± 0.09 kpc (27,700 ly) |
| Apparent Angular Diameter | arcmin | 20.0 ± 1.0′ (Class V) | 14.0 ± 1.0′ (Class IV) |
| Iron Abundance [Fe/H] | dex | −1.53 ± 0.04 dex | −2.31 ± 0.05 dex |
| Isochrone Turnoff Age | Gyr | 11.65 ± 0.45 Gyr | 12.80 ± 0.40 Gyr |
Astrophysical & Observational Synthesis
Messier 92 is one of the oldest and most metal-poor globular clusters in the entire Milky Way: at [Fe/H] = −2.31 dex (less than 1/200th solar iron abundance) and an isochrone turnoff age of ~12.8 Gyr, it formed more than a billion years earlier than intermediate-metallicity Messier 13 ([Fe/H] = −1.53 dex, ~11.65 Gyr) during the earliest collapse of the Galactic halo.
Dynamically, M92 exhibits a tighter Shapley–Sawyer Class IV core concentration than Class V M13. Even though M92 sits 15% farther away (8.50 kpc vs 7.42 kpc) and is 0.64 magnitudes fainter in total integrated light, its compact central core shines with a surface brightness that nearly rivals M13's center in medium-aperture telescopes.
Related Reference Guides
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.
Surface Brightness & Extended Objects Guide
Why surface brightness (mag/arcsec²) governs nebula and galaxy visibility more than integrated magnitude, and how exit pupil controls eyepiece contrast.
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.
Primary Catalogs & Scientific Sources
- 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