NGC 581

Also Known as: Messier 103 (M103), Collinder 14

Object Type: Open Cluster

Constellation: Cassiopeia

Distance from Earth: 10,000 Light years

Apparent Magnitude: 7.4

Coordinates: RA 01H 33.3M 0S DEC 60deg 42min 0sec

Actual Size: 17.5 light years in diameter

Apparent Dimensions: 6.0 arc-minutes

Discovered by: Messier 103 was discovered by the French astronomer Pierre Méchain in March or April 1781. Méchain described the object as a “cluster of stars between Epsilon & Delta of the leg of Cassiopeia”.
Along with the galaxies M101 and M102, M103 was one of the last minute additions to the Messier catalogue. Messier did not get a chance to observe and verify Méchain’s three discoveries before publication. M103 was the last object to be entered by Messier himself.
The Sombrero Galaxy (M104) and the remaining Messier objects (M105 to M110) were added to the catalogue much later, in the 20th century.

Description: There are several other open clusters located in this area of the sky, including NGC 654, NGC 659 and NGC 663, the last of which is sometimes confused with M103.
Messier 103 is one of the smallest and most remote open clusters known.
It contains 172 confirmed members. The brightest stars in the cluster have a visual magnitude of 10.5 and belong to spectral classes B5 Ib and B2 III, which means that they are a supergiant and giant star, both white-blue in color.
Most of the cluster’s brightest members are young, hot, blue stars.
At the center of the cluster, there is a prominent red giant with a visual magnitude of 10.8.
The star is classified as belonging to the spectral class M6 III or gM6. Messier 103 is moving toward us at 37 km/s.
Struve 131, a 7th magnitude multiple star system, dominates the cluster, but is not a member and only appears in the same line of sight.
The triple star lies in the foreground and is much closer to us than M103. The primary component in the system is a blue supergiant.
The estimated age of the cluster is about 25 million years, only 30 percent of the age of the Pleiades (M45).

Click Below Image(s) for Full Size:

M103 is easy to see, even with binoculars, and appears as a nebulous fan-shaped patch. 4-inch telescopes resolve the four brightest stars in the cluster.
Large telescopes resolve more stars across the cluster, but make it harder to make out M103 from the surrounding star field because the cluster is quite loose.

The best time of year to observe M103 is during the winter, but northern observers can see it at any time of year. The cluster is circumpolar and never sets below the horizon north of latitude 30N.

Platesolve

NGC 581 Cluster

Imaging Details
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