NGC 637
Open star cluster in the constellation Cassiopeia
title: "NGC 637" type: doc version: 1 created: 2026-02-28 author: "Wikipedia contributors" status: active scope: public tags: ["open-clusters", "ngc-objects", "cassiopeia-(constellation)", "discoveries-by-william-herschel", "astronomical-objects-discovered-in-1787"] description: "Open star cluster in the constellation Cassiopeia" topic_path: "general/open-clusters" source: "https://en.wikipedia.org/wiki/NGC_637" license: "CC BY-SA 4.0" wikipedia_page_id: 0 wikipedia_revision_id: 0
::summary Open star cluster in the constellation Cassiopeia ::
::data[format=table title="Infobox cluster"]
| Field | Value |
|---|---|
| name | NGC 637 |
| image | [[File:NGC 0637 DSS.jpg |
| epoch | J2000.0 |
| constellation | Cassiopeia |
| ra | |
| dec | |
| dist_ly | 2.160 ± |
| appmag_v | 8.2 |
| size_v | 4.2′ |
| age | 10 ± 5 Myr |
| names | |
| :: |
| name = NGC 637 | image = [[File:NGC 0637 DSS.jpg|NGC 637 DSS|300px]] | epoch = J2000.0 | constellation = Cassiopeia | ra = | dec = | dist_ly = 2.160 ± | appmag_v = 8.2 | size_v = 4.2′ | mass_kg = | mass_msol = | radius_ly = | v_hb = | age = 10 ± 5 Myr | notes = | names =
NGC 637 is an open cluster of stars in the northern constellation of Cassiopeia, positioned about 1.5° to the WNW of the star Epsilon Cassiopeiae. The cluster was discovered on 9 November 1787 by German-born English astronomer William Herschel. It is located in the Perseus Arm of the Milky Way, at a distance of approximately 7,045 light years from the Sun. The cluster is small but compact, and is readily visible in a small telescope.
This is a young cluster with an estimated age of 5–15 million years. It has a Trumpler class of I2m, indicating it is strongly concentrated (I) with an intermediate range of brightness variation (2) and a moderate richness of stars (m). The cluster has 55 members and an angular radius of 4′.2, corresponding to a physical radius of 3.0 pc. It has a core radius of .
The seven brightest members are all over 10th magnitude, with five known to be variable. A total of four β Cephei-type variables have been identified, one of the highest such totals for an open cluster. A classical Be star candidate has been detected. The distribution of the cluster's stars on the Hertzsprung–Russell diagram shows a noticeable gap on the main sequence, which is not explained by missing data.
References
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