Messier 37 (NGC 2099)
Coordinates, Gaia DR3 distance (1.42 kpc), magnitude 5.6, central red giant HD 250068, and observing guide for Messier 37 in Auriga.
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) | 5.6 mag | ± 0.1 mag | Integrated wide-field photometry | definitive | Revised New General Catalogue and Index Catalogue (RNGC/IC) |
| Heliocentric distance | 4630 ly | ± 100 ly | Gaia DR3 astrometric parallax of ~2,000 members (1.42 ± 0.03 kpc) (J2016.0) | definitive | ESA Gaia Archive — Data Release 3 |
| Apparent diameter | 24 arcmin | ± 2 arcmin | Member star-count boundary | high-confidence | Revised New General Catalogue and Index Catalogue (RNGC/IC) |
| Main-sequence turnoff & white-dwarf age | 0.5 Gyr | ± 0.05 Gyr | Gaia DR3 turnoff isochrone + white-dwarf cooling sequence | high-confidence | ESA Gaia Archive — Data Release 3 |
J2000 Equatorial Sky Chart & Culmination Altitude
The chart below plots Messier 37 (NGC 2099 Salt-and-Pepper Cluster) at RA 05h 52m 18.00s, Dec +32° 33′ 14.0″ within Auriga, 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 37 (NGC 2099, the Salt-and-Pepper Cluster) is the brightest, richest, and oldest of the three famous Messier open clusters in Auriga, lying 4,630 light-years (1.42 ± 0.03 kiloparsecs) away toward the Galactic anticenter. First logged by Giovanni Battista Hodierna before 1654, M37 was completely missed by Guillaume Le Gentil in 1749 before Charles Messier independently rediscovered it on September 2, 1764.
Spanning 24 arcminutes on the sky (~33 light-years physically), M37 packs more than 2,000 gravitationally bound stars and a total dynamical mass of ~3,600 solar masses into a Trumpler Class I 1 r profile. Because it is roughly 500 million years old—twenty times older than neighboring M36—its original massive B-type stars have long since evolved off the main sequence, leaving behind over 35 golden-orange red-clump giants and dozens of white dwarfs.
In 2023, deep ultraviolet and optical spectroscopy of a large planetary nebula superposed on M37 confirmed that its central white dwarf (WD J0552+3237) shares the cluster's exact radial velocity and proper motion—making it one of only three confirmed planetary nebulae physically bound inside a Milky Way open cluster.
Practical Visual Observing Guide
- Located 4.8° southwest of Theta Aurigae (Mahasim) just outside the southern border of the Auriga pentagon, 3.8° east-southeast of M36.
- In 10×50 binoculars M37 is the largest and brightest of the Auriga trio, appearing as a smooth, glowing 5.6-magnitude cloud that resembles a globular cluster.
- Through a 100–200 mm telescope at 60×–120×, M37 explodes into a dense cloud of over 150 stars of uniform 10th-to-12th magnitude brightness anchored at the very center by a solitary 9.2-magnitude orange-red giant.
Catalog Cross-Identifications & Aliases
Common Aliases: M37 · NGC 2099 · Salt-and-Pepper Cluster · Auriga Salt-and-Pepper
| Catalog Authority | Identifier |
|---|---|
| MESSIER | M 37 |
| NGC | NGC 2099 |
| SIMBAD | M 37 |
| WIKIDATA | Q11393 |
Related Objects, Comparisons & Guides
Pinwheel Cluster (Messier 36 / NGC 1960)
Coordinates, Gaia DR3 distance (1.17 kpc), magnitude 6.0, young B-star kinematics, and observing guide for Messier 36 in Auriga.
Starfish Cluster (Messier 38 / NGC 1912)
Coordinates, Gaia DR3 distance (1.13 kpc), magnitude 6.4, binary cluster pair NGC 1907, and observing guide for Messier 38 in Auriga.
Wild Duck Cluster (Messier 11 / NGC 6705)
Coordinates, Gaia DR3 distance (1.88 kpc), magnitude 5.8, alpha-enhanced bulge chemistry, and observing guide for M11 in Scutum.
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
- 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
- Revised New General Catalogue and Index Catalogue (RNGC/IC) (2024/2026 edition): Steinicke, W. 2010, Observing and Cataloguing Nebulae and Star Clusters (Cambridge Univ. Press); Verga, M. OpenNGC (CC-BY-SA 4.0 / data tables) — Wolfgang Steinicke / OpenNGC
- 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