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.
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) | 6.4 mag | ± 0.1 mag | Wide-aperture integrated photometry | definitive | Revised New General Catalogue and Index Catalogue (RNGC/IC) |
| Heliocentric distance | 3685 ly | ± 80 ly | Gaia DR3 astrometric parallax of cluster members (1.13 ± 0.025 kpc) (J2016.0) | definitive | ESA Gaia Archive — Data Release 3 |
| Apparent diameter | 21 arcmin | ± 2 arcmin | Member star-count boundary | high-confidence | Revised New General Catalogue and Index Catalogue (RNGC/IC) |
| Main-sequence turnoff age | 0.29 Gyr | ± 0.04 Gyr | Gaia DR3 color-magnitude diagram isochrone fitting | high-confidence | ESA Gaia Archive — Data Release 3 |
J2000 Equatorial Sky Chart & Culmination Altitude
The chart below plots Starfish Cluster (Messier 38 / NGC 1912) at RA 05h 28m 41.00s, Dec +35° 51′ 19.0″ 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 38 (NGC 1912, the Starfish Cluster) is the northernmost and loosest of the three Messier open clusters in Auriga, located 3,685 light-years (1.13 ± 0.025 kiloparsecs) from Earth—virtually the same distance from the Sun as its young neighbor M36 just 2.3 degrees to the southeast. Recorded by Giovanni Battista Hodierna before 1654 and rediscovered independently by Guillaume Le Gentil in 1749, M38 spans 21 arcminutes on the sky (~23 light-years physically).
At an age of roughly 290 million years, M38 sits midway in evolutionary state between 25-million-year-old M36 and 500-million-year-old M37. Its brightest member is a yellow-orange G0 III giant shining at visual magnitude 7.9, surrounded by hundreds of B5 to A-type main-sequence stars arranged in intersecting chains that Admiral William Henry Smyth described as 'an oblique cross, with a pair of large stars in each arm' and modern observers compare to a five-armed starfish or the Greek letter Pi (π).
Just 30 arcminutes south-southwest of M38 sits the compact, 8.2-magnitude open cluster NGC 1907, creating a celebrated wide-field telescopic double alongside the colored optical pair Lyon 19.
Practical Visual Observing Guide
- Located nearly dead-center along the line joining Theta Aurigae (Mahasim) and Iota Aurigae (Hassaleh), 2.3° northwest of M36.
- In 10×50 binoculars M38 is a large, soft 6.4-magnitude glow that pairs nicely with tighter M36 in the same field.
- Use an 80–150 mm telescope at 35×–60× to trace the cross- or Pi-shaped stellar arms of M38 while framing compact NGC 1907 30′ to the south-southwest in the same eyepiece view.
Catalog Cross-Identifications & Aliases
Common Aliases: M38 · NGC 1912 · Starfish Cluster
| Catalog Authority | Identifier |
|---|---|
| MESSIER | M 38 |
| NGC | NGC 1912 |
| SIMBAD | M 38 |
| WIKIDATA | Q11395 |
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.
Messier 37 (NGC 2099 Salt-and-Pepper Cluster)
Coordinates, Gaia DR3 distance (1.42 kpc), magnitude 5.6, central red giant HD 250068, and observing guide for Messier 37 in Auriga.
Messier 35 (NGC 2168 & NGC 2158 Pair)
Coordinates, Gaia DR3 distance (889 pc), magnitude 5.1, background cluster NGC 2158 contrast, and observing guide for M35 in Gemini.
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.
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