(Pleiades, The Seven Sisters)
As we look up into the cosmos, the stars appear to be floating motionless in a sea of black…docile and fixed. Nothing could be further from the truth. An example of the dramatic motion of the stars is seen here in this image of Pleiades, also known as the Seven Sisters. This familiar grouping found in the constellation Taurus, lies about 450 light years away from us. The seven major stars are actually just seven of an estimated 1000 stars that are part of this open cluster of stars that is moving through space as a gravitationally bound group. The open cluster spans about 80 light years.
For many years astronomers believed the nebulosity surrounding these stars to be the remnants of the molecular clouds that gave birth to the stars. More recently, it has become clear that these clouds are not related to the star field at all. In fact, the star cluster, which is traveling at about 45 kilometers per second (162,000 km/hr), has crashed into this preexisting interstellar cloud. The chaos of the collision is reflected in the many diverse tendrils of nebulosity moving in a variety of directions. Most of the stars are young, hot A,B stars, which are probably less than 100 million years old.
As a side note, Astronomers using the Gemini and Spitzer telescopes, recently identified what appears to be the remnants of 2 planets or planetesimals that collided which were orbiting the star HD 23514. This star is in the Pleiades cluster, and slightly out of the Field of view of the image shown above.
Image acquisition info:
Date: November 2007
Locations: Starlodge observatory, Ione, CA
Telescope: FSQ 106
Camera: STL 11000