Hyades (star cluster)
Open cluster in the constellation Taurus / From Wikipedia, the free encyclopedia
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The Hyades (/ˈhaɪ.ədiːz/; Greek Ὑάδες, also known as Caldwell 41, Collinder 50, or Melotte 25) is the nearest open cluster and one of the best-studied star clusters. Located about 153 light-years (47 parsecs)[1][2][3][4] away from the Sun, it consists of a roughly spherical group of hundreds of stars sharing the same age, place of origin, chemical characteristics, and motion through space.[1][5] From the perspective of observers on Earth, the Hyades Cluster appears in the constellation Taurus, where its brightest stars form a "V" shape along with the still-brighter Aldebaran. However, Aldebaran is unrelated to the Hyades, as it is located much closer to Earth and merely happens to lie along the same line of sight.
Hyades Cluster | |
---|---|
Observation data (J2000.0 epoch) | |
Right ascension | 4h 27m |
Declination | +15° 52′ |
Distance | 153 ly (47 pc[1][2][3][4]) |
Apparent magnitude (V) | 0.5 |
Apparent dimensions (V) | 330′ |
Physical characteristics | |
Mass | 400 M☉ |
Radius | 10 light-years (core radius) |
Estimated age | 625 million years |
Closest open cluster | |
Other designations | Caldwell 41, Cr 50, Mel 25 |
Associations | |
Constellation | Taurus |
See also: Open cluster, List of open clusters |
The five brightest member stars of the Hyades have consumed the hydrogen fuel at their cores and are now evolving into giant stars.[6] Four of these stars, with Bayer designations Gamma, Delta 1, Epsilon, and Theta Tauri, form an asterism that is traditionally identified as the head of Taurus the Bull.[6] The fifth of these stars is Theta1 Tauri, a tight naked-eye companion to the brighter Theta2 Tauri. Epsilon Tauri, known as Ain (the "Bull's Eye"), has a gas giant exoplanet candidate,[7] the first planet to be found in any open cluster.
The age of the Hyades is estimated to be about 625 million years.[1] The core of the cluster, where stars are the most densely packed, has a radius of 8.8 light-years (2.7 parsecs), and the cluster's tidal radius – where the stars become more strongly influenced by the gravity of the surrounding Milky Way galaxy – is 33 light-years (10 parsecs).[1] However, about one-third of confirmed member stars have been observed well outside the latter boundary, in the cluster's extended halo; these stars are probably in the process of escaping from its gravitational influence.[1]