Bode's Galaxy (Messier 81 / NGC 3031)
Coordinates, Cepheid/TRGB distance (3.63 Mpc / 11.8 Mly), magnitude 6.94, M81–M82 tidal pair, and observing guide for Bode's Galaxy in Ursa Major.
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) | 6.94 mag | ± 0.05 mag | Integrated wide-field CCD photometry | definitive | Revised New General Catalogue and Index Catalogue (RNGC/IC) |
| Extragalactic distance | 3630000 pc | ± 140000 pc | HST Key Project Cepheids + TRGB (3.63 ± 0.14 Mpc / 11.84 Mly) | definitive | SH0ES Local Distance Ladder Hubble Constant |
| Apparent major axis | 26.9 arcmin | ± 1 arcmin | Optical isophotal dimensions (26.9′ × 14.1′) | definitive | Revised New General Catalogue and Index Catalogue (RNGC/IC) |
| Heliocentric radial velocity | -34 km/s | ± 4 km/s | H I 21-cm systemic velocity (slight blueshift due to Solar Galactic rotation) | definitive | SIMBAD Astronomical Database (CDS) |
J2000 Equatorial Sky Chart & Culmination Altitude
The chart below plots Bode's Galaxy (Messier 81 / NGC 3031) at RA 09h 55m 33.17s, Dec +69° 03′ 55.0″ within Ursa Major, 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
Bode's Galaxy (Messier 81, NGC 3031), discovered by Johann Elert Bode on New Year's Eve 1774 in northern Ursa Major, is one of the brightest and cleanest grand-design spiral galaxies in the sky at magnitude 6.94. Located 3.63 ± 0.14 megaparsecs (11.84 million light-years) from Earth, M81 is the gravitational anchor of the M81 Group—the nearest galaxy group outside our own Local Group, containing roughly three dozen galaxies.
Approximately 200 to 300 million years ago, M81 underwent a close gravitational encounter with its neighbors Messier 82 (the Cigar Galaxy, lying just 37 arcminutes north) and NGC 3077. Radio 21-centimeter maps with the Very Large Array reveal huge streams and bridges of neutral hydrogen gas linking all three galaxies, while the tidal interaction amplified M81's two symmetrical spiral arms and funneled gas into its 70-million-solar-mass central black hole.
In March 1993 a red supergiant in M81's inner spiral arm exploded as Supernova 1993J (a Type IIb event similar to Cassiopeia A's progenitor), reaching magnitude 10.7 and becoming the second-brightest supernova of the 20th century after SN 1987A.
Practical Visual Observing Guide
- Extend a diagonal line from Phad (γ UMa) through Dubhe (α UMa) in the Big Dipper's bowl by the same distance (~10°) northwest to land directly on the M81/M82 pair.
- Because M81 and M82 sit only 37 arcminutes apart, any binocular or telescope at 30×–60× frames both galaxies in the same field of view—an oval, bright-cored spiral (M81) paired with a narrow edge-on slash (M82).
Catalog Cross-Identifications & Aliases
Common Aliases: M81 · NGC 3031
| Catalog Authority | Identifier |
|---|---|
| MESSIER | M 81 |
| NGC | NGC 3031 |
| SIMBAD | M 81 |
| WIKIDATA | Q14024 |
Related Objects, Comparisons & Guides
Cigar Galaxy (Messier 82 Starburst Galaxy)
Coordinates, TRGB distance (3.53 Mpc / 11.5 Mly), starburst superwind, dark dust filaments, and observing guide for the Cigar Galaxy (M82).
Whirlpool Galaxy (Messier 51 / NGC 5194)
Coordinates, SN II-P / TRGB distance (8.58 Mpc / 28.0 Mly), grand-design spiral arms, NGC 5195 tidal companion, and observing guide for M51.
Andromeda Galaxy (Messier 31 / NGC 224)
Coordinates, Cepheid/TRGB distance (765 kpc / 2.50 Mly), magnitude 3.44, blueshift (−300 km/s), and observing guide for Andromeda (M31).
Mizar & Alcor (Zeta Ursae Majoris System)
Coordinates, Hipparcos/VLBI distance (82.8 ly), 11.8′ naked-eye pair, 14.4″ Mizar A–B split, and observing guide for Mizar & Alcor.
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Scientific Sources & Dataset Provenance
- 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
- SH0ES Local Distance Ladder Hubble Constant (2022 Baseline Cepheid + SN Ia): Riess, A. G., et al. 2022, ApJL, 934, L7 (A Comprehensive Measurement of the Local Value of the Hubble Constant) — SH0ES Collaboration (HST / JWST)
- 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