Messier 19 (NGC 6273)
Coordinates, Gaia DR3 distance (8.34 kpc), magnitude 6.77, extreme ellipticity, iron spread, and observing guide for Messier 19 in Ophiuchus.
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) | 6.77 mag | ± 0.06 mag | Integrated photoelectric & CCD photometry | definitive | Catalog of Parameters for Milky Way Globular Clusters |
| Heliocentric distance | 27200 ly | ± 600 ly | Gaia EDR3 + kinematic bulge distance (8.34 ± 0.18 kpc) (J2016.0) | high-confidence | ESA Gaia Archive — Data Release 3 |
| Apparent major axis | 17 arcmin | ± 1.5 arcmin | Elliptical surface-density profile (E3–E4 oblateness) | high-confidence | Revised New General Catalogue and Index Catalogue (RNGC/IC) |
| Isochrone turnoff age | 12.1 Gyr | ± 0.6 Gyr | Differential-reddening-corrected HST CMD fitting | model-dependent | Catalog of Parameters for Milky Way Globular Clusters |
J2000 Equatorial Sky Chart & Culmination Altitude
The chart below plots Messier 19 (NGC 6273 Oblate Globular) at RA 17h 02m 37.80s, Dec -26° 16′ 04.6″ within Ophiuchus, 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 19 (NGC 6273) is the most noticeably oblate (elliptical) globular cluster in the entire Messier catalog, located 27,200 light-years (8.34 ± 0.18 kiloparsecs) from Earth in southern Ophiuchus—and just 5,200 light-years from the Galactic center. Discovered by Charles Messier on June 5, 1764, M19 exhibits an apparent axial ratio of roughly 3:2 (ellipticity E3 to E4) elongated north-northwest to south-southeast.
Two physical factors combine to give M19 its strongly oval silhouette. First, the cluster orbits deep inside the Milky Way's central bulge potential where intense tidal forces stretch its outer envelope along a 17-arcminute major axis. Second, high-resolution dust mapping reveals a foreground lane of interstellar extinction across the eastern rim that selectively dims one side of the halo, exaggerating the optical asymmetry.
Even more remarkably, high-resolution spectroscopy has established that M19 belongs to the rare class of 'iron-complex' globular clusters alongside Omega Centauri and M22. Its roughly one million stars divide into at least two main metallicity groups at [Fe/H] ≈ −1.75 and −1.50 dex, plus a third metal-rich tail enriched in s-process elements, suggesting that NGC 6273 is the surviving nuclear remnant of a disrupted dwarf galaxy.
Practical Visual Observing Guide
- Located 7.7° almost due east of Antares (α Scorpii), along the southern border of Ophiuchus.
- In 10×50 binoculars or an 80 mm telescope at 50×, M19's north-south oval shape is immediately apparent even before individual stars are resolved.
- A 150–250 mm telescope at 130×–180× resolves the cream-colored core into 14th-magnitude red giants while preserving its distinctive egg-shaped outline.
Catalog Cross-Identifications & Aliases
Common Aliases: M19 · NGC 6273
| Catalog Authority | Identifier |
|---|---|
| MESSIER | M 19 |
| NGC | NGC 6273 |
| SIMBAD | M 19 |
| WIKIDATA | Q11349 |
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 22 (NGC 6656 Sagittarius Cluster)
Coordinates, Gaia DR3 distance (3.30 kpc), magnitude 5.10, stellar-mass black holes, and observing guide for Messier 22 in Sagittarius.
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.
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.
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.
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