| M52 - Open Cluster
in Cassiopeia - sometimes called The Salt &
Pepper Cluster Mag 7.3, 13 arcminutes across RA 23:24.2 Dec 61 35' |
The Bubble Nebula -
NGC7635 -
Sh2-162 Mag ?.? 40 arcminutes across RA 23:21 Dec 61 14' |
NGC7538 9 arcminutes RA 23:14 Dec 61 34' |
Discovered 1774 by Charles Messier.
M52 is a fine open cluster located in a rich Milky Way field. It is one of the rich clusters for which amateur Jeff Bondono has proposed the name "salt and pepper" clusters. Ake Wallenquist (1959) found 193 probable members in a region of 9' radius, and the density near the center is about 3 stars per cubic parsec.
The Sky Catalogue 2000.0 gives an age of only 35 million years.
The distance of this cluster is not very well known; adopting our value of 5,000 light years, the cluster's apparent diameter of 13.0 arc minutes corresponds to a linear extension of 19 light years.
Open cluster M52 is one of the original discoveries of Charles Messier, who cataloged it on September 7, 1774 when the comet of that year came close to it.
Amateurs can see M52 as a nebulous patch in good binoculars or finder scopes. In 4-inch telescopes, it appears as a fine, rich compressed cluster of faint stars, often described as of fan or "V" shape; the bright yellow star is to the SW edge.
Situated about 35' SW of M52 is the Bubble Nebula NGC 7635, a diffuse nebula which appears as a large, faint and diffuse oval, about 3.5x3' around the 7th-mag star HD 220057 of spectral type B2 IV. It is difficult to see because of its low surface brightness. Just immediately south of M52 is the little conspicuous open cluster Czernik 43 (Cz 43), which is visible in larger telescopes only.
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