The "Seven" Sisters? - The Pleiades Open Star Cluster

 High overhead in the evening during the winter is the beautiful bright open star cluster known as the Pleiades.

The name of the Pleiades comes from Ancient Greek. It probably derives from plein ("to sail") because of the cluster's importance in delimiting the sailing season in the Mediterranean Sea: "the season of navigation began with their heliacal rising". However, in mythology the name was used for the Pleiades, seven divine sisters, the name supposedly deriving from that of their mother Pleione and effectively meaning "daughters of Pleione".

So why are the Pleiades called the Seven Sisters, when only six stars can be seen with the eye? In fact, the number of stars you can see within the Pleiades cluster, using just your eye, varies depending on your own eyesight, local atmospheric transparency and light pollution levels. Some people simply see fainter stars than others. It’s possible that early skywatchers, whose skies were darker and clearer than our modern skies, more often saw more than six stars here. Even today, people with exceptional vision see seven, eight or more stars in the Pleiades with the unaided eye. With binoculars you can easily see far more!

The Bible mentions this star cluster (that is easily visible to the unaided human eye) in Job 9:9 and Job 38:31 as well as in Amos 5:8. It has been known since antiquity to cultures all around the world, including the Celts, Irish, Hawaiians, Aboriginal Australians, the Persians, the Arabs, the Chinese, the Japanese (who call them Subaru), the Maya, the Aztec, the Sioux, the Kiowa and the Cherokee... any many more!

With small telescopes or average binoculars, but especially when long-exposure photographs are taken some hint of nebulosity around the cluster is seen. The "veil" around the bright blue stars is called a reflection nebula, caused by dust reflecting the blue light of the hot, young stars.

Studies show that the dust responsible for the nebulosity is not uniformly distributed, but is concentrated mainly in two layers along the line of sight to the cluster. These layers may have been formed by deceleration due to radiation pressure as the dust has moved towards the stars. - Wikipedia

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