They are Rare and Will be Gone Soon in Astronomical Time. These Seven Sisters are a Great Destination for Your Celestial Observations.
The Pleiades are a unique cluster of stars that burst into light 75 to 150 million years ago and will disperse across the sky in a little more than 250 million years. This is due to both the gravitational effects of the Milky Way Galaxy and giant, molecular clouds in the vicinity. That number of years is a fairly brief event in cosmological time. At a distance of a little less than 400 light years away from our Sun, it's relatively close as a group. There is some controversy about its actual distance but many sources cite 400 light years on average. It's estimated to be 4.5 light years wide at its core radius and up to 50 light years wide at its outer edge. It's been determined that many stars in the cluster are traveling at 40 kilometers a second with many moving in opposite directions.
Above image by: NASA, ESA, AURA/Caltech, Palomar Observatory
Their appearance and arrangement is similar to the Plough (Big Dipper) but on a much smaller and dimmer scale. Dark-night viewing is the best way to see The Pleiades and binoculars or a reduced magnification on a telescope will allow you to see the full cluster. A large aperture with its ability to capture light can help as well.
Many of the stars appear hazy and surrounded by complex, blue filaments of light. This is due to dust particles in a large nebula that cuts across the cluster. According to the Kitt Peak Observatory a second cloud is also evident creating a unique combination of interstellar events.
Sometimes referred to as the Seven Sisters, six stars are apparent with the naked eye, but any magnification will bring the seventh and others into view. In fact, it's estimated more than 1,000 stars reside in the cluster although there are some estimates that put the number as high as 3,000. It's also known as M45, Messier 45 and "Subaru" in Japanese.
Map of M45. Image by: NASA, ESA and AURA/Caltech
How To Find the Pleiades
The constellation Orion is a good place to start if you're having trouble locating The Pleiades. Simply imagine a line through Orion's belt and look to your right. You'll notice a V-shaped arrangement of stars. This is the head of Taurus the Bull. The brightest star in the "V" is Aldebaran. To the right of Aldebaran you'll notice a small dipper configuration - that's The Pleiades.
Much like Orion, The Pleiades are considered a winter event in the Northern hemisphere fading below the horizon in late April and re-emerging in September. November is the prime month with The Pleiades high in the sky.
Once you've located the Pleiades and spent some time studying this unique cluster - you'll find it very easily and turn to its shimmering, blue light often.
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Find more on: Observing the Night Sky
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