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Open Star Cluster of the Hyades

Date:25.1.00 Time:20:16 UT Exposure:30 min
Field of View:14.7o x 10.0o Emulsion: Kodak Royal Gold 400 Select Filter:none
Instrument:f=135mm 1/2.8 Place:Lichtenhagen Observer:T. Credner

© Copyright by the observers

The scattered group of stars in the central part of the image is the Open Star Cluster of the Hyades in the constellation of Taurus. On the left hand side you can recognize the smaller cluster NGC 1647. The Hyades, also called Melotte 25, can be seen easily by naked eye as a distinct V in the sky. However you should be aware that the brightest star Aldebaran, which represents the red eye of the bull in myth, does physically not belong to the cluster population.

The Hyades play a quite major role in astrophysics. The rich star cluster is so close that the distance can be measured by geometrical methods, i.e. classical parallaxes of the individual stars or the so called "convergent-point" method which gives a distance to the cluster center. Getting this distance gives a fundamental step of the distance ladder to our galaxy and even further out to extragalactic objects.
Based on observations by the astrometric Hipparcos satellite trigonometric parallaxes to the individual stars could be measured with high accuracy. This parallax is the apparent annual motion of a star caused by our change of perspective when the earth orbits around the sun. The closer the star, the bigger is its parallax motion. The measurements yield a distance of 46.34 ± 0.27 pc to the clusters center.

References:

  • 1998A&A...331...81P, Perryman et.al., The Hyades: distance, structure, dynamics, and age
  • Hyades in 3D from the paper above
  • Jean-Claude Mermilliod's WEBDA page about the Hyades
  • SEDS Infos