01 November 2009

Close Encounter of the Pleiades and Moon

The Pleiades is one of the most beautiful star clusters in the sky. In Autumn it rises during the evening and its distinctive glow shines even for urban dwellers. The Pleiades, also known as M45 (from the Messier Catalog), is a collection of relatively young stars (only 100 million years old!) that shine with a blue color due to their hot temperature. The Pleiades are also known as the Seven Sisters and there is plenty of mythology describing each of the seven sisters. Despite the "Seven Sisters" mythology, most people see six stars when they look out at the Pleiades and describe the shape of the asterism as a small Little Dipper. Random fact: the Subaru car company logo is made up of six the stars, Subaru being the Japanese term for Pleiades.

This week on Tuesday evening the full moon passes very close to the Pleiades and in more southerly latitudes it actually occults (blocks out) several of the brightest stars in the cluster. For those of us in San Francisco, the evening of November 3rd should be especially interesting if you view the Moon through binoculars or a telescope. You will be able to notice how fast the Moon moves past the stars of the Pleiades. Although the very bright light of the full Moon will drown out nearly everything around it (including the blue nebulosity of the dust surrounding the Pleiades), all will be clear when you look closely with binoculars or a telescope.

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