Hyades (star cluster)
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The Hyades (‘Υάδες) are an open star cluster located in the constellation Taurus. The closest obvious star cluster to Earth (the Ursa Major Moving Group is closer, many astronomers consider the Sun to be inside it, but it is more spread out in the sky as a consequence), it is centered some 151 light years away. The brightest star in this direction is Aldebaran, but it is not a member of the cluster, being located at just over 40% of the distance. Not counting Aldebaran, approximately 300 stars are known or suspected to be members of the cluster; most are not visible to the naked eye.
The stars of the Hyades are associated with one another in the sense that they are all moving in approximately the same direction and at the same speed through the galaxy. Plotting their movements backwards eventually brings them all to a more or less a single point about 600-800 million years ago, a fact explained by the theory that they all formed in the same stellar nursery. The same 600-800 million year age is inferred by the main sequence turnoff method of estimating the age of a cluster of stars by reasoning that the cluster age cannot be greater than the lifetime of the most luminous stars main sequence stars found within the cluster. The stars of the Praesepe star cluster have a similar age and space velocity, and may also be related to the Hyades.
The common space motion of the Hyades stars was only demonstrated in 1908 by astronomer Lewis Boss, but the Hyades have been known since antiquity. The name itself dates back at least as far as 1000 BC, when it is mentioned in various Greek sources.
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