NGC 884

NGC 884
The Double Cluster, NGC 869 (top) and NGC 884 (bottom) with north to the left
Observation data (J2000 epoch)
Right ascension02h 22.0m
Declination+57° 08′
Distance7.6 kly (2.3 kpc)
Apparent magnitude (V)6.1
Apparent dimensions (V)18′
Physical characteristics
Estimated age14 Myr
Other designationsCaldwell 14, Cr 25, Mel 14, Raab 10, OCl 353, Chi Per Cluster, χ Persei
Associations
ConstellationPerseus
See also: Open cluster, List of open clusters

NGC 884 (also known as χ Persei) is an open cluster of stars located 7,640 light years away in the constellation of Perseus. It is the east component of the Double Cluster with NGC 869. NGC 869 and 884 are often designated h and χ Persei, respectively. The cluster is about 14 million years old. Located in the Perseus OB1 association, both clusters are located physically close to one another, only a few hundred light years apart. The clusters were first recorded by Hipparchus, thus have been known since antiquity.

The two clusters are often photographed or observed by amateur astronomers with small telescopes. The clusters are visible with the unaided eye between the constellations of Perseus and Cassiopeia as a brighter patch in the winter Milky Way. The Double Cluster was also included in the Caldwell catalogue, a catalogue of astronomical objects for amateur observation.

In small telescopes, the cluster appears as a group of bright stars in a rich star field. Most of its bright stars are blue, with a few orange stars. Both clusters can be seen together at low magnification.

References

  1. 1 2 3 "NGC 884". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2006-12-22.
  2. 1 2 3 4 Currie, Thayne; Hernandez, Jesus; Irwin, Jonathan; Kenyon, Scott J.; Tokarz, Susan; Balog, Zoltan; Bragg, Ann; Berlind, Perry; Calkins, Mike (2010). "The Stellar Population of h and χ Persei: Cluster properties, membership, and the intrinsic colors and temperatures of stars". The Astrophysical Journal Supplement. 186 (2): 191. arXiv:0911.5514. Bibcode:2010ApJS..186..191C. doi:10.1088/0067-0049/186/2/191. S2CID 16454332.
  3. 1 2 3 Finlay, Warren H. (2014). Concise Catalogue of Deep-Sky Objects. The Patrick Moore Practical Astronomy Series (2nd ed.). Springer Cham. p. 167. doi:10.1007/978-3-319-03170-5. ISBN 978-3-319-03169-9.
  4. 1 2 O'Meara, Stephen James (2002). The Caldwell Objects. Cambridge University Press. ISBN 978-0-521-82796-6.
  5. ↑ Some confusion surrounds what Bayer intended by these designations. It is sometimes claimed that Bayer could not have resolved the pair into two patches of nebulosity, and that χ (chi) refers to the Double Cluster and h to a nearby star; see Stephen James O'Meara and Daniel W.E. Green, 2003, "The Mystery of the Double Cluster", Sky and Telescope, Vol. 105, No. 2 (February 2003), p. 116–119. Bayer's Uranometria chart for Perseus does not show them as nebulous objects, but his chart for Cassiopeia does, and they are described as Nebulosa Duplex in Schiller's Coelum Stellatum Christianum, which was assembled with Bayer's help; see Morton Wagman, Lost Stars, McDonald & Woodward, 2003, ISBN 0939923785, p. 240.