Sunflower Galaxy (Messier 63 / NGC 5055)
J2000 coordinates, TRGB distance (29.3 Mly), magnitude 8.59, flocculent spiral arms, warped H I disk, and observing guide for Messier 63 (NGC 5055).
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) | 8.59 mag | ± 0.08 mag | Integrated wide-field CCD photometry | definitive | Revised New General Catalogue and Index Catalogue (RNGC/IC) |
| Distance in light-years | 29300000 ly | ± 900000 ly | HST Tip of the Red Giant Branch (TRGB: 8.99 ± 0.28 Mpc) | definitive | SH0ES Local Distance Ladder Hubble Constant |
| Apparent major axis | 12.6 arcmin | ± 0.5 arcmin | Optical 25 mag/arcsec² isophotal dimensions (12.6′ × 7.2′) | definitive | Revised New General Catalogue and Index Catalogue (RNGC/IC) |
| Heliocentric recession velocity | 497 km/s | ± 3 km/s | H I 21-cm synthesis rotation curve | definitive | SIMBAD Astronomical Database (CDS) |
J2000 Equatorial Sky Chart & Culmination Altitude
The chart below plots Sunflower Galaxy (Messier 63 / NGC 5055) at RA 13h 15m 49.30s, Dec +42° 01′ 45.4″ within Canes Venatici, 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 63 (NGC 5055), universally known as the Sunflower Galaxy, holds a special place in astronomical history as the very first deep-sky discovery made by Charles Messier's colleague Pierre Méchain on June 14, 1779. Lying 29.3 million light-years away in Canes Venatici as a major sibling of the Whirlpool Galaxy (M51) group, M63 spans roughly 107,000 light-years across its main stellar disk and is inclined 55 degrees to our line of sight.
Whereas M51 is the textbook example of a two-armed 'grand-design' spiral driven by tidal waves, M63 is the premier astronomical archetype of a 'flocculent' (fleece-like) spiral galaxy. In optical light, its disk breaks into dozens of short, discontinuous, overlapping spiral segments and dusty star-forming feathers wound tightly around a bright yellow central bulge like the seed pattern of a sunflower—though near-infrared Spitzer imaging at 3.6 microns reveals a smooth, underlying two-armed stellar density wave beneath the patchy young star clouds.
Deep neutral-hydrogen 21-centimeter radio maps and ultra-deep optical exposures show that M63's gaseous disk extends to more than twice its optical diameter (~40 kiloparsecs) with a pronounced S-shaped warp, encircled by a giant looping stellar stream forged when M63 tidally disrupted and cannibalized a dwarf satellite galaxy billions of years ago.
Practical Visual Observing Guide
- Located 5.5° north-northeast of Cor Caroli (α Canum Venaticorum) and 6° south-southwest of M51; a 9th-magnitude foreground field star sits right on the western tip of M63's halo, looking like a permanent supernova!
- Visible as a bright 8.6-mag oval glow in 10×50 binoculars and any 60–80 mm refractor.
- In a 200–300 mm telescope at 120×–180×, the bright core is surrounded by a grainy, mottled disk whose sharper southern edge marks a prominent dust lane.
Catalog Cross-Identifications & Aliases
Common Aliases: M63 · NGC 5055 · UGC 8334 · Sunflower Galaxy
| Catalog Authority | Identifier |
|---|---|
| MESSIER | M 63 |
| NGC | NGC 5055 |
| SIMBAD | M 63 |
| WIKIDATA | Q13984 |
Related Objects, Comparisons & Guides
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.
Cat's Eye Galaxy (Messier 94 / NGC 4736)
J2000 coordinates, TRGB distance (15.0 Mly), magnitude 8.24, blazing inner starburst ring, outer pseudoring, and observing guide for Messier 94.
Messier 106 (NGC 4258 Megamaser Anchor)
J2000 coordinates, geometric maser distance (24.7 Mly), magnitude 8.41, anomalous synchrotron arms, Seyfert 2 core, and observing guide for M106.
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.
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.
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