The Pleiades (M45)

The Pleiades, “The Sisters”, is undoubtedly the best known star cluster in the heavens, easily studied in binoculars.

The story of the Seven Sisters is quickly told.

Strikingly apparent in a fairly empty part of the sky, it shouldn't be necessary to point out The Pleiades. However just to make sure you've got it right, start at Bellatrix (gamma Orion, the upper right corner as you view Orion). Put your thumb on Bellatrix and forefinger on Aldebaran. Now holding this width, move your hand to the northwest. Just before your thumb hits Aldebaran your forefinger will have met The Pleiades.

While the cluster sometimes goes by the name of “The Seven Sisters” several hundred stars make up the cluster. Ten of these carry names, listed below.

Most of the fainter members are grouped toward the western edge. The brightest, Alcyone, is roughly in the centre while Mum and Dad (Pleione and Atlas) are found on the eastern edge.

  The named members of The Pleiades, from top to bottom, starting on the western edge:

    Sterope (or Asterope, 21 and 22 Tauri), two stars 5.76 and 6.4 visual magnitude, form a fairly dim top of a small triangle. You might be challenged to split these two close stars.
    Taygete (19 Tau) is just below and a bit to the west, brighter at 4.30. Taygete is one of the more prominent of the sisters; she bore a son (Lacedaemon) by Zeus and the son grew to become the king of Sparta.
    Maia (20 Tau), 3.87, rounds out this little triangle. She was the eldest of the daughters, known for her beautiful hair. She had an even more notable son by Zeus, Hermes (known to the Romans as Mercury).
    Celaeno (16 Tau), 5.45, is next, fainter and a bit farther to the west. Just below this star is ...
    Electra (17 Tau), 3.72, who had two sons by Zeus, Dardanus and Iasion. Dardanus built a city at the foot of Mount Ida, which later became known as Troy. Thus he is considered the founder of the Trojans. He is said to have been his father's favourite son.
       Iasion also had a momentous life; he produced two sons with Demeter and was considered a god by the Arcadians.

    Now curving to the east, the southern most star is Merope (23 Tau), 4.14. Merope was the only sister to marry a mortal -- Sisyphus, the king of Corinth, whom Zeus later afflicted with the punishment of pushing a large stone up a hill which, just as it reached the top, rolled back down again, and so Sisyphus pushed it up again ... for eternity.

      Alcyone (eta Tauri), the brightest member with a visual magnitude of 2.85. While the brightest star, she didn't have a particularly momentous life, having a number of offspring with Poseidon.
          This star sits alone, apart from her other sisters and the two parents, which are found on the eastern edge:
      Pleione (28 Tau): 5.05, the mother of the others, is found above. The star is a noted variable.
      Atlas (27 Tau): 3.62, lies to the south of Pleione. Not only the sisters' father, Atlas also fathered many more (the Hesperides, the Hyades, Calypso and so on). Atlas angered Zeus by taking the side of the Titans in their argument with Zeus. For this indiscretion Atlas was saddled with the weight of the world.

    The entire group is enveloped in a very faint nebulosity, the remainder of the stellar nursery that produced the stars. This nebulosity is nearly invisible in telescopes and only clearly evident in long-exposure photography. Occasionally, depending on the quality of the skies, the area around Merope shows evidence of this nebula.

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