|Observation data (J2000.0 epoch)|
|Right ascension||01h 33.2m|
|Distance||8.5 kly ()|
|Apparent magnitude (V)||7.4|
|Apparent dimensions (V)||6.0'|
Messier 103 (also known as M103, or NGC 581) is an w:open cluster in the w:constellation Cassiopeia. It was discovered by w:Pierre Méchain in w:1781. M103 is at a distance of about 8,000 w:light-years from w:Earth.