Hyades (star cluster)

( Let it rain Greek hyein, ) the Hyades, even rain or Taurus star - power, are an open star cluster in the constellation Taurus, which can be observed with the naked eye. They are easy to find as a V- shaped arrangement of the brightest stars of the cluster directly on the main star of Taurus, Aldebaran. Aldebaran itself, however, does not belong to the Hyades. In the Messier and NGC catalog of star clusters is not listed in Melotte catalog it is listed as Melotte 25.

Details

The star cluster is visible in Central Europe from September to April in the northern night sky. The core of the Hyades has a diameter of about 4 parsecs, external cluster members can still be found within a radius of up to 24 pc. The distance is about 44 pc, age about 600 million years, so a little older than the Pleiades. The overall brightness corresponds to a brightness of about 1 mag. Together with the Pleiades, the Hyades form the golden gate of the ecliptic.

Because of their uniform motion in space the Hyades group is also counted among the motion clusters. It is characterized by the uniform change in location of all the stars on a virtual point of convergence and comprises about 350 stars that s move uniformly with about 43 km / in this direction. This point, also referred to as " Vertex ", located just east of Betelgeuse in the constellation Orion. Proper motion, age and composition of the Hyades are similar to those of the Praesepe star cluster, suggesting a common origin of both clusters, although they are now hundreds of light -years apart.

Due to the proximity to our solar system, the Hyades play an important role in modern astrophysics. The distance and thus the absolute brightness of the individual stars of the star cluster basis of classical trigonometric methods ( parallax star and current parallax) can be accurately determined. Then build other measuring methods to more distant objects, even outside our galaxy on what includes in particular the Cepheids.

Mythological Background

In Greek mythology, the Hyades were daughters of Atlas and Aethra. Her only brother, Hyas was killed in the hunt. My grief and tears excited the pity of the gods, and so they were placed as Hyades among the stars. Even Virgil speaks of the "wet Hyades ", and the ancient Greek name " rain star " reveals the importance of: the tears flow continue unchecked, rush now as rain.