NGC 6087 (also known as Caldwell 89 or the S Normae Cluster) is an

open cluster An open cluster is a type of star cluster made of up to a few thousand stars that were formed from the same giant molecular cloud and have roughly the same age. More than 1,100 open clusters have been discovered within the Milky Way galaxy, and ...

of 40 or more Burnham's ''Celestial Handbook'' gives the number 40, though other studies go as high as 349; see Stephen James O'Meara, ''The Caldwell Objects'', Cambridge University Press, 2002, p. 351. stars centered on the

Cepheid variable A Cepheid variable () is a type of star that pulsates radially, varying in both diameter and temperature and producing changes in brightness with a well-defined stable period and amplitude. A strong direct relationship between a Cepheid varia ...

S Normae S Normae (S Nor) is a yellow supergiant variable star in the constellation Norma. It is the brightest member of the open cluster NGC 6087. S Normae is a Classical Cepheid variable with a visual magnitude range of 6.12 to 6.77 and a pe ...

in the

constellation A constellation is an area on the celestial sphere in which a group of visible stars forms Asterism (astronomy), a perceived pattern or outline, typically representing an animal, mythological subject, or inanimate object. The origins of the e ...

Norma Norma may refer to: * Norma (given name), a given name (including a list of people with the name) Astronomy *Norma (constellation) * 555 Norma, a minor asteroid *Cygnus Arm or Norma Arm, a spiral arm in the Milky Way galaxy Geography *Norma, Lazi ...

. At a distance of about 3500 ly and covering a field of almost one quarter of a degree, the stars range from seventh- to eleventh-magnitude, the brightest being 6.5 magnitude S Normae. The aggregate visual magnitude of the cluster is about 5.4. Spectral analysis of the radial motion of the stars confirm that S Normae is a member of the cluster, and the period/luminosity relationship of Cepheid variables allows the distance to be determined with confidence.

References

External links

* * {{DEFAULTSORT:NGC 6087 Open clusters Norma (constellation) 6087 089b