Hercules cluster

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Hercules cluster,

giant globular 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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 in the northern constellation HerculesHercules
, in astronomy, northern constellation located between Lyra and Corona Borealis. It is traditionally depicted as the hero Hercules in a kneeling position. There are no very bright stars in Hercules and only three of third magnitude, the brightest of which, Ras Algethi
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; cataloged as M13 or NGC 6205. The cluster is just visible to the naked eye and is the best example of a globular cluster visible in the Northern Hemisphere. Its angular diameter is about 2-3 that of the full moon, and its linear diameter is 100 light-yearslight-year,
in astronomy, unit of length equal to the distance light travels in one sidereal year. It is 9.461 × 1012 km (about 6 million million mi). Alpha Centauri and Proxima Centauri, the stars nearest our solar system, are about 4.3 light-years distant.
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. The entire cluster contains perhaps 100,000 or more stars. In its central portion, the stars are so close together that they cannot be resolved, despite the cluster's relatively near distance of 35,000 light-years; the separation between stars is estimated to be only a few astronomical unitsastronomical unit
(AU), mean distance between the earth and sun; one AU is c.92,960,000 mi (149,604,970 km). The astronomical unit is the principal unit of measurement within the solar system, e.g., Mercury is just over 1-3 AU and Pluto is about 39 AU from the sun.
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 as compared to the normal interstellar separation of a few light-years.

Hercules cluster

[′hər·kyə‚lēz ‚kləs·tər]
(astronomy)
A cluster of about 75 bright galaxies with a recession velocity of 6200 miles (10,000 kilometers) per second.
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