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.
Collins Dictionary of Astronomy © Market House Books Ltd, 2006

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.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.
References in periodicals archive ?
The Wild Duck Cluster got its name from the shape of its brightest stars, which "form a 'V' shape that somewhat resembles a flock of ducks in flight." Considered to be among the "richest and most compact open clusters" discovered by man, Messier 11 is believed to have formed around 220 million years ago, according to (https://www.nasa.gov/image-feature/goddard/2019/hubble-spots-flock-of-cosmic-ducks) NASA's website.
Our final stop is the open cluster Stock 2, reclining on the Cassiopeia-Perseus border, 4[degrees] east-southeast of NGC 663.
But the group is worth a closer look in any telescope, because it guards a well-kept secret off its eastern end: the small, faint open cluster NGC 6802.
Kharchenko, Piskunov and Roeser place most of the stars within the radius of their open cluster, COCD 1034 = ASCC 34 = [KPR2005] 34 and list the position of the magnitude 8 star HD 54779 as the cluster's centre (Webb Society journal 144).
Open clusters often take on a particular shape through the eyepiece that is not obvious in photographs or drawings, and this cluster has earned the moniker of the Owl Cluster--not just for the two bright stars that represent the owl's eyes, but for the other stars whose patterns form the body, the legs and the wings--or perhaps visual observers just have a very vivid imagination.
"Our galaxy contains more than 1,000 of these open clusters, which potentially can present the physical conditions for harbouring many more of these giant planets," Perez said.
Binoculars show a small compact open cluster with one reddish star.
IC 4756 is another open cluster nearby that's also visible by naked eye under dark sky, and even bigger (although a little sparser) than NGC 6633 next door.
Star clusters can either be a group of stars bound together by gravity that soon exit out of the cluster, called open clusters, while other clusters contain groups of ancient stars, called globular clusters.
Snugly protected by the Scutum shield, and approximately 1.50 north-east of the open cluster NGC 6631, is the diffuse nebula IC 1287.
In fact Cancer is unusual in that its brightest deep sky object, the open cluster M44, has an integrated magnitude that is brighter than any of the stars within the constellation, and often M44 is the only part of Cancer that can be seen with the naked eye.
Now let's sweep over to another open cluster, M23, which can fit in a binocular field of view with the star marked Mu ([mu]) on our chart.

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