M 103
Scientific overview
M 103 is an open cluster in the constellation Cassiopeia. It shines at apparent magnitude 7.4 and spans about 4.5 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 · M 103
| Distance | 6,722 ly | SIMBAD · catalogued |
| Physical size (major axis) | 8.799186 ly | SIMBAD · derived |
| Radial velocity | -45.33 ± 0.32 km/s | SIMBAD · measured |
| Right ascension (ICRS) | 23.339167 deg | SIMBAD · measured |
| Declination (ICRS) | 60.658889 deg | SIMBAD · measured |
Full field-level provenance
- Distance: Centre de données astronomiques de Strasbourg (CDS) · SIMBAD · mesDistance · dist · 2019MNRAS.486.5726D · distance indicator: paral · catalogued value · source value 2061 pc · 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
- Radial velocity: Centre de données astronomiques de Strasbourg (CDS) · SIMBAD · basic · rvz_radvel · 2019MNRAS.486.5726D · direct catalogue measurement · retrieved 2026-07-11
- Right ascension (ICRS): Centre de données astronomiques de Strasbourg (CDS) · SIMBAD · basic · ra · 2021A&A...647A..19T · direct catalogue measurement · retrieved 2026-07-11
- Declination (ICRS): Centre de données astronomiques de Strasbourg (CDS) · SIMBAD · basic · dec · 2021A&A...647A..19T · 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). This is a Galactic object: its Doppler shift is shown as a radial velocity, not a cosmological redshift. Fields a source did not provide are omitted, never invented.
Other objects in Cassiopeia
| Object | Type | Mag | Size (′) |
|---|---|---|---|
| Owl ClusterC 13 · NGC 457 | Open cluster | 6.4 | 7.8 |
| IC 1805 | Cluster with nebulosity | 6.5 | 60 |
| IC 1848 | Cluster with nebulosity | 6.5 | 40 |
| NGC 129NGC 129 | Open cluster | 6.5 | 5.4 |
| NGC 654NGC 654 | Open cluster | 6.5 | 6.3 |
| NGC 1027NGC 1027 | Open cluster | 6.7 | 7.8 |
| NGC 7789NGC 7789 | Open cluster | 6.7 | 14.4 |
| M 52M 52 · NGC 7654 | Open cluster | 6.9 | 9.9 |
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.