Messier 80 (NGC 6093)
Coordinates, Gaia DR3 distance (10.34 kpc), magnitude 7.33, Nova T Scorpii 1860, blue-straggler core, and observing guide for M80 in Scorpius.
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) | 7.33 mag | ± 0.05 mag | Integrated photoelectric & CCD photometry | definitive | Catalog of Parameters for Milky Way Globular Clusters |
| Heliocentric distance | 33700 ly | ± 450 ly | Gaia EDR3 parallax + HST dynamical modeling (10.34 ± 0.14 kpc) (J2016.0) | high-confidence | ESA Gaia Archive — Data Release 3 |
| Apparent tidal diameter | 10 arcmin | ± 0.8 arcmin | Surface-brightness profile fitting | high-confidence | Revised New General Catalogue and Index Catalogue (RNGC/IC) |
| Main-sequence turnoff age | 12.7 Gyr | ± 0.5 Gyr | HST ACS color-magnitude turnoff fitting | model-dependent | Catalog of Parameters for Milky Way Globular Clusters |
J2000 Equatorial Sky Chart & Culmination Altitude
The chart below plots Messier 80 (NGC 6093 Dense Scorpius Globular) at RA 16h 17m 02.41s, Dec -22° 58′ 33.9″ within Scorpius, 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 80 (NGC 6093) is one of the most densely packed globular clusters in the Milky Way, situated 33,700 light-years (10.34 ± 0.14 kiloparsecs) away in northern Scorpius. Discovered by Charles Messier on January 4, 1781, and called by William Herschel 'the richest and most condensed mass of stars which the firmament can offer,' M80 packs roughly 340,000 solar masses of ancient stars into a physical diameter of 95 light-years with an ultra-compact Shapley-Sawyer Class II concentration.
On May 21, 1860, German astronomer Arthur Auwers discovered a blazing 7.0-magnitude 'new star'—Nova 1860 AD, or T Scorpii—Just 6 arcseconds from M80's center. For several days, that single thermonuclear white-dwarf eruption outshone the entire half-million-star cluster combined before fading back below 12th magnitude by mid-June.
Hubble Space Telescope ultraviolet imaging of M80's core uncovered more than 300 blue straggler stars—twice as many as in any other globular cluster surveyed by HST. Because M80 has not yet reached full gravothermal core collapse, its sky-high collision rate indicates that the cluster is currently caught in a brief, high-density transitional phase supported by primordial binary burning and stellar collisions.
Practical Visual Observing Guide
- Situated midway between Antares (α Scorpii) and Graffias (β Scorpii), just 4.3° northwest of M4, offering a dramatic visual contrast between one of the loosest (M4, Class IX) and one of the tightest (M80, Class II) globulars in the sky.
- In binoculars and small 80–100 mm telescopes, M80 looks remarkably like a bright tailless comet head with a blazing core and a sharp edge.
- A 200–300 mm telescope at 180×–260× is needed to resolve its 14.2-magnitude red giants around the outer halo.
Catalog Cross-Identifications & Aliases
Common Aliases: M80 · NGC 6093
| Catalog Authority | Identifier |
|---|---|
| MESSIER | M 80 |
| NGC | NGC 6093 |
| SIMBAD | M 80 |
| WIKIDATA | Q11503 |
Related Objects, Comparisons & Guides
Messier 4 (NGC 6121 Nearest Globular)
Coordinates, Gaia DR3 distance (1.85 kpc), magnitude 5.63, central stellar bar, and Antares finder guide for Messier 4 in Scorpius.
Messier 19 (NGC 6273 Oblate Globular)
Coordinates, Gaia DR3 distance (8.34 kpc), magnitude 6.77, extreme ellipticity, iron spread, and observing guide for Messier 19 in Ophiuchus.
Messier 2 (NGC 7089 Globular Cluster)
Coordinates, Gaia DR3 distance (11.69 kpc), magnitude 6.47, Gaia-Enceladus origin, and observing guide for Messier 2 (NGC 7089) in Aquarius.
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.
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
- 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