open cluster

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open cluster:

see star clusterstar cluster,
a group of stars near each other in space and resembling each other in certain characteristics that suggest a common origin for the group. Stars in the same cluster move at the same rate and in the same direction.
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open cluster

(galactic cluster) A loose cluster of stars that contains at most a few thousand stars and sometimes fewer than twenty. Examples visible to the naked eye are the Hyades and the Pleiades. About 1200 open clusters are known. They are population I systems and occur in or close to the plane of the Galaxy. The brightest stars in an open cluster can be either red or blue giants, depending upon its age. Stars in the older clusters, such as M67 in Cancer, are similar in appearance to those in globular clusters, although with some subtle differences due to the higher metal content of the material from which they were formed. Open clusters are more loosely bound systems than globular clusters and they tend to be gradually dispersed by the combined effects of the differential rotation of the Galaxy and perturbations due to close encounters with interstellar clouds. Calculations suggest that many will not survive more than one or two circuits of the Galaxy. Hence most open clusters are comparatively young systems. Some, such as NGC 2264, are less than 10 million years old and in these clusters star-formation is probably still taking place (see OB cluster). See also Hertzsprung–Russell diagram; moving cluster; turnoff point.

open cluster

[′ō·pən ′kləs·tər]
(astronomy)
One of the groupings of stars that are concentrated along the central plane of the Milky Way; most have an asymmetrical appearance and are loosely assembled, and the stars are concentrated in their central region; they may contain from a dozen to many hundreds of stars. Also known as galactic cluster.
References in periodicals archive ?
This makes it middle-aged by open star cluster standards [1].
For instance, Canis Major offers a fine open star cluster just 4[degrees] south of (below) Sirius, in the same binocular field of view.
Right on the north-western boundary, the open star cluster NGC 5823 is literally bisected by the constellations Circinus and Lupus.
An easy target for smaller telescopes is the bright and fairly large open star cluster M34.
Named after the astronomical open star cluster of the same name, NASA's Pleiades system now consists of three generations of SGI Altix ICE, three generations of Intel[R] Xeon[R] processor series, and two generations of InfiniBand, all managed as a single system, demonstrating the power and flexibility of Altix ICE to span multiple generations.
The open star cluster NGC 3231 is located in the far north of the constellation.
By the morning of August 25th, Venus has crossed into Cancer, where the planet ends the month as it began: on the verge of passing a big open star cluster, in this case M44, the Beehive.
Sweeping a bit farther north takes us to the open star cluster NGC 1981.
From 61 Cygni we'll take a long step out to the open star cluster known as the Hyades (Caldwell 41) in Taurus.
Some asterisms have no distinctive shape or image, resembling nothing but an open star cluster.
In front of it is M11, as fine an open star cluster as exists anywhere in the heavens.