Open Cluster Messier 103

Messier 103
Messier 103: Section of the STScI Digitized Sky Survey [147]


The open star cluster M 103 was discovered by Pierre Méchain on 27 March 1781. He described it as a «cluster of stars between ε and δ of the legs of Cassiopeia». [281]

Physical Properties

M 103 is of the Trumpler type III2p. It is about 7'100 light years away from us and is approaching us at a speed of 45 km/s. A striking feature is the double star Struve 131 (ADS 1209, HD 9311) in the northwest of the cluster. Its two stars are 7.2 mag and 9.8 mag bright and 13.9 arc seconds apart. The double star does not belong to the cluster. [145]

Revised+Historic NGC/IC, Version 22/9, © Dr. Wolfgang Steinicke [277]
DesignationNGC 581
TypeOCL (III2p)
Right Ascension01h 33m 23.0s
Declination+60° 39' 30"
Diameter6 arcmin
Visual magnitude7.4 mag
Metric Distance2.194 kpc
Dreyer DescriptionCl, pL, B, R, Ri, st 10…11
Identification, RemarksM 103, OCL 326

Finder Chart

The open star cluster M 103 is located in the constellation Cassiopeia between the stars Segin (ε Cassiopeiae) and Ruchbah (δ Cassiopeiae). The constellation is highest in the months of July to January.

Chart Open Cluster Messier 103
Open Cluster Messier 103 in constellation Cassiopeia. Chart created using SkySafari 6 Pro and STScI Digitized Sky Survey. [149, 160]

More Objects Nearby (±15°)


145SIMBAD astronomical database;
147Aladin Lite; (2020-12-23)
149SkySafari 6 Pro, Simulation Curriculum;
160The STScI Digitized Sky Survey;
277«Historische Deep-Sky Kataloge» von Dr. Wolfgang Steinicke; (2021-02-17)
281«Catalogue Nébuleuses et des Amas D'Étoiles» Observées à Paris, par M. Messier, à l'Observatoire de la Marine, hôtel de Clugni, rue des Mathurins. «Connoissance des temps ou connoissance des mouvements célestes, pour l'année bissextile 1784 » Page 227; (2021-02-21)