NGC 869 (also known as h Persei) is an

open cluster An open cluster is a type of star cluster made of tens 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 around 7,460

light year A light-year, alternatively spelled light year (ly or lyr), is a unit of length used to express astronomical distance, astronomical distances and is equal to exactly , which is approximately 9.46 trillion km or 5.88 trillion mi. As defined by t ...

s away in the constellation of

Perseus In Greek mythology, Perseus (, ; Greek language, Greek: Περσεύς, Romanization of Greek, translit. Perseús) is the legendary founder of the Perseid dynasty. He was, alongside Cadmus and Bellerophon, the greatest Greek hero and slayer of ...

. The cluster is around 14 million years old. It is the west component 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 to the ...

with NGC 884. 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. 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.Morton Wagman, ''Lost Stars'', McDonald & Woodward, 2003, , p. 240. 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 Hipparchus (; , ; BC) was a Ancient Greek astronomy, 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 equinoxes. Hippar ...

, 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

and Cassiopeia as a brighter patch in the winter

Milky Way The Milky Way or Milky Way Galaxy is the galaxy that includes the Solar System, with the name describing the #Appearance, galaxy's appearance from Earth: a hazy band of light seen in the night sky formed from stars in other arms of the galax ...

. 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

External links

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NGC 869 at SEDSNGC 869 at Messier45
{{DEFAULTSORT:NGC 0869 Open clusters Perseus (constellation) 0869 Persei, h 014b Astronomical objects known since antiquity