Saturday, August 2, 2014

M45, the Pleiades, the Seven Sisters

This remarkable open cluster is perhaps the most viewed object in the sky in the whole history of humanity and in my opinion it is the most beautiful cluster. The Pleiades is mention in the literature of many ancient cultures such as the Mayans, Hindus, Chinese, Aztecs, Persians, Arabs, and Jews to name a few. In the end, the name “Pleiades” was adopted from the Greek.

Located in the constellation of Taurus, finding the Pleiades is really easy and basically it doesn’t need reference stars as it is very obvious even in a very light polluted sky.  Look at the Taurus region of the sky and find a big triangle formed by six stars (one of them is a double star) included the orange giant star Aldebaran; then go in the north-west direction and there is M45. From my skies, it seems like a fuzzy spot that looks like an ice cream cone shape with the edges undefined. Forcing my eyes a little, I could discern at least 5 of the 7 brightest stars set into a like nebulous area barely sensed. Even though the perception of a nebulous background could be caused by an optical effect of the stars that cannot be resolved with the naked eye view, about 500 that form the cluster, in fact, there is a reflection nebulae associated with the cluster and better perceived in long exposure photography.

If the field of view is wider it looks like the sense of nebulosity is stronger. So, I recommend a wide field of view such as the binoculars to enjoy this show.

In the binocular view sketch I made in September of 2012 (this was one the first I made) I believed I could discern some of the nebulosity by using averted vision. But the sense of view was varied: sometimes it looked nebulous and sometimes, by using direct vision, it looked like an optical illusion given off by the stunning glow of the brightest stars. By referring to other observers notes I learned that it is possible to see the nebula area behind the star Merope (the one located at the right-most position of the diamond in the binocular sketch) by using averted vision in this area in a dark enough sky while trying to avoid the shining of the star.  This area is well known as NGC 1435, The Merope Nebula.

The brightest stars in the cluster are catalogued as hot B-type stars; they shine blue in long exposure photographs. In my observations, they appeared to shine in a brilliant white color that had a strong contrast with the stars around that seemed to shine in a weak pale white color.

Finally, let me quote a part of the Bible verse written by the prophet Amos between 767 and 753 BC about this stunning deep sky object: “He who made the Pleiades…the LORD is his name” Amos 5:8, New international version.

Thanks for reading this entry and I hope you have had a nice time with it.



Edited by Jennifer Steinberg (editor in chief)


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