NGC 884 (also known as χ Persei) 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 ...

located 7640

light year A light-year, alternatively spelled light year, is a large unit of length used to express astronomical distances and is equivalent to about 9.46 trillion kilometers (), or 5.88 trillion miles ().One trillion here is taken to be 1012 ...

s away in the constellation of Perseus. It is the easternmost of the

Double Cluster The Double Cluster (also known as Caldwell 14) consists of the open clusters NGC 869 and NGC 884 (often designated h Persei and χ (chi) Persei, respectively), which are close together in the constellation Perseus. Both visible with the ...

with

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

. NGC 869 and 884 are often designated h and χ Persei, respectively.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 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, , p. 240. The cluster is about 14 million years old. Located in the

Perseus OB1 Perseus OB1 is an OB association in the Northern Celestial Hemisphere in the constellation Perseus. It is centered around the double cluster (NGC 869 and NGC 884), and has lent its name to the Perseus Arm of the Milky Way. The brightest member of ...

association, both clusters are located physically close to one another, only a few hundred light years apart. The clusters were first recorded by

Hipparchus Hipparchus (; el, Ἵππαρχος, ''Hipparkhos''; BC) was a Greek astronomer, geographer, and mathematician. He is considered the founder of trigonometry, but is most famous for his incidental discovery of the precession of the equi ...

, thus have been known since antiquity. The Double Cluster is a favorite of amateur astronomers. These bright clusters are often photographed or observed with small telescopes. Easy to find, the clusters are visible with the unaided eye between the constellations of

Perseus In Greek mythology, Perseus (Help:IPA/English, /ˈpɜːrsiəs, -sjuːs/; Greek language, Greek: Περσεύς, Romanization of Greek, translit. Perseús) is the legendary founder of Mycenae and of the Perseid dynasty. He was, alongside Cadmus ...

and Cassiopeia as a brighter patch in the winter

Milky Way The Milky Way is the galaxy that includes our Solar System, with the name describing the galaxy's appearance from Earth: a hazy band of light seen in the night sky formed from stars that cannot be individually distinguished by the naked eye ...

. The Double Cluster was also included in the

Caldwell catalogue The Caldwell catalogue is an astronomical catalogue of 109 star clusters, nebulae, and galaxies for observation by amateur astronomers. The list was compiled by Patrick Moore as a complement to the Messier catalogue. While the Messier catalog ...

, a catalogue of astronomical objects for amateur observation. In small telescopes, the cluster appears as a beautiful assemblage of bright stars located in a rich star field. Dominated by bright blue stars, the cluster also hosts a few orange stars that add to the visual interest. Both clusters together offer a spectacular low-magnification view.

References

External links

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NGC 884 at SEDSNGC 884 at Messier45
{{DEFAULTSORT:NGC 0884 Open clusters Perseus (constellation) 0884 Persei, Chi Astronomical objects known since antiquity