Reflection Nebulosity
Under ideal observing conditions, some hint of nebulosity may be seen around the cluster, and this shows up in long-exposure photographs. It is a reflection nebula, caused by dust reflecting the blue light of the hot, young stars.
It was formerly thought that the dust was left over from the formation of the cluster, but at the age of about 100 million years generally accepted for the cluster, almost all the dust originally present would have been dispersed by radiation pressure. Instead, it seems that the cluster is simply passing through a particularly dusty region of the interstellar medium.
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.
Read more about this topic: Pleiades
Famous quotes containing the word reflection:
“With respect to a true culture and manhood, we are essentially provincial still, not metropolitan,—mere Jonathans. We are provincial, because we do not find at home our standards; because we do not worship truth, but the reflection of truth; because we are warped and narrowed by an exclusive devotion to trade and commerce and manufacturers and agriculture and the like, which are but means, and not the end.”
—Henry David Thoreau (1817–1862)