NGC 869

NGC 869 (also known as h Persei) is an open cluster located 7460 light years away in the constellation of Perseus.^[2] The cluster is about 14 million years old.^[2] It is the westernmost of the Double Cluster with NGC 884.

NGC 869
The Double Cluster, NGC 869 (right) and NGC 884 (left) with north to the top
Observation data (J2000 epoch)
Right ascension	02h 19.1m [1]
Declination	+57° 09′[1]
Distance	7.5 kly[2] (2.3 kpc[2])
Apparent magnitude (V)	3.7[1]
Physical characteristics
Radius	33.15 ly
Estimated age	14 Myr[2]
Other designations	Caldwell 14, Cr 24,[1] Mel 13,[1] h Per,[1] h Persei[1]
Associations
Constellation	Perseus
See also: Open cluster, List of open clusters

NGC 869 and 884 are often designated h and χ (chi) Persei, respectively. Some confusion surrounds what Bayer intended by these designations. It is sometimes claimed that Bayer did not resolve the pair into two patches of nebulosity, and that χ refers to the Double Cluster and h to a nearby star.^[3] 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.^[4] The clusters are both located in the Perseus OB1 association, a few hundred light years apart from each other. The clusters were first recorded by Hipparchus, thus have been known since antiquity.

The Double Cluster is often photographed and observed 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. In small telescopes the cluster appears as an assemblage of bright stars located in a rich star field. Dominated by bright blue stars, the cluster also hosts a few orange stars.

References

1. "NGC 869". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2006-12-22.
2. 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. 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.
4. Morton Wagman, Lost Stars, McDonald & Woodward, 2003, ISBN 0939923785, p. 240.

External links

• Media related to NGC 869 at Wikimedia Commons
• NGC 869 at SEDS
• NGC 869 at Silicon Owl
• NGC 869 at Messier45^{[permanent dead link‍]}