M 101
Scientific overview
M 101 is a barred spiral galaxy in the constellation Ursa Major. It shines at apparent magnitude 7.9 and spans about 23.99 arcminutes of sky.
Observation guide
Guidance follows standard observing practice, derived from the object's real magnitude and position. A dark, moonless sky always helps.
Location in the sky
Precision measurements
Distances and velocities from SIMBAD and redshift from NED · M 101
| Distance | 2.1852e+7 ly | SIMBAD · catalogued |
| Physical size (major axis) | 152,496 ly | SIMBAD · derived |
| Physical size (minor axis) | 146,647 ly | SIMBAD · derived |
| Redshift (z) | 0.000804 ± 7.0000e-6 | NED · catalogued |
| Radial velocity | 243.033094 km/s | SIMBAD · measured |
| Right ascension (ICRS) | 210.802429 deg | SIMBAD · measured |
| Declination (ICRS) | 54.34875 deg | SIMBAD · measured |
Full field-level provenance
- Distance: Centre de données astronomiques de Strasbourg (CDS) · SIMBAD · mesDistance · dist · 2011ApJS..192....6L · distance indicator: T-F · catalogued value · source value 6.7 Mpc · retrieved 2026-07-11
- Physical size (major axis): Centre de données astronomiques de Strasbourg (CDS) · derived (OpenNGC angular size × SIMBAD distance) · physical size = angular size × distance (small-angle); angular size from OpenNGC, distance from SIMBAD mesDistance · derived · retrieved 2026-07-11
- Physical size (minor axis): Centre de données astronomiques de Strasbourg (CDS) · derived (OpenNGC angular size × SIMBAD distance) · physical size = angular size × distance (small-angle); angular size from OpenNGC, distance from SIMBAD mesDistance · derived · retrieved 2026-07-11
- Redshift (z): NASA/IPAC Extragalactic Database · NED · ObjectLookup · Redshift · 2023ApJ...955L...8H · catalogued value · NED quality S1L · retrieved 2026-07-11
- Radial velocity: Centre de données astronomiques de Strasbourg (CDS) · SIMBAD · basic · rvz_radvel · 2012A&A...545A..15S · direct catalogue measurement · retrieved 2026-07-11
- Right ascension (ICRS): Centre de données astronomiques de Strasbourg (CDS) · SIMBAD · basic · ra · 2006AJ....131.1163S · direct catalogue measurement · retrieved 2026-07-11
- Declination (ICRS): Centre de données astronomiques de Strasbourg (CDS) · SIMBAD · basic · dec · 2006AJ....131.1163S · direct catalogue measurement · retrieved 2026-07-11
Physical size is derived from the OpenNGC angular size and the catalogued distance (small-angle: size = angle × distance). Redshift is the object's measured redshift — a negative value is a blueshift (the galaxy is approaching, its motion dominated by local rather than cosmic expansion). Fields a source did not provide are omitted, never invented.
Other objects in Ursa Major
| Object | Type | Mag | Size (′) |
|---|---|---|---|
| Bode's GalaxyM 81 · NGC 3031 | Spiral galaxy | 6.92 | 21.63 |
| Cigar GalaxyM 82 · NGC 3034 | Spiral galaxy | 8.3 | 10.99 |
| NGC 3184NGC 3184 | Barred spiral galaxy | 9.84 | 7.4 |
| NGC 2768NGC 2768 | Elliptical galaxy | 9.87 | 5.64 |
| M 109M 109 · NGC 3992 | Spiral galaxy | 9.88 | 8.07 |
| NGC 3077NGC 3077 | Spiral galaxy | 9.88 | 5.21 |
| Owl NebulaM 97 · NGC 3587 | Planetary nebula | 9.9 | 3.58 |
| M 108M 108 · NGC 3556 | Spiral galaxy | 10.05 | 3.98 |
Sources
The primary and reference sources this topic draws on.
- OpenNGCOpenNGC (M. Verga) — NGC/IC, Messier, and Caldwell catalogue data
Openly-licensed deep-sky catalogue: object types, positions, magnitudes, sizes, morphology, and cross-identifiers.