Wednesday, November 27, 2013

Astronomy Picture of the Day: 11/27/13 - Pleiades

This is the Pleiades star cluster as you"ve never seen it before -- in deep field! Also known as M45 or the Seven Sisters, Pleiades is probably one of the most famous and well-studied star clusters in the galaxy. Although it lies some 400 light-years away from Earth toward the constellation of Taurus, it can still be seen with the naked eye in cities that have mild to severe light pollution problems. Get away from the lights of big cities, one should easily be able to see the brightest six stars of the cluster. Obviously, there are many more stars than just the seven (although the exact number remains unknown). An additional 1,000 stars, which span about 43 light-years in radius, have been confirmed (together, they have an estimated mass of about 800 individual suns)

This particular image of Pleiades was taken with an exposure of about 30 HOURS. It covers a portion of sky that is several times larger than the size of a full moon. The massive stars contained within the region are very hot, metal-poor stars that live fast and die young, spewing large quantities of gas and heavier elements out into the interstellar medium once they go supernova. Some of which, shine hundreds of times more brightly than the sun does. The faintest of the bunch is still 40 times more luminous than the sun would appear from the same distance, with Alcyone being over 1,000 times more luminous!

As an interesting side note; most people are only able to clearly make out six of the stars in the Pleiades cluster. Regardless, over the years, speculation surfaced concerning the existence of a seventh star that could be easily made out in the cluster. If this is the case, It"s possible that the seventh star could be a variable star (like our sun is). Meaning, it varies in brightness over time. It"s also possible, in theory, that the "missing" star isn"t missing at all, but that the star is hidden from view by thick pockets of interstellar dust grains.

To see additional information about this region, see: %UR:%

Image Credit: Stanislav Volskiy

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