The Beginning

The substance known as Dark Matter has many intelligent minds asking serious questions about the properties of the Universe. No one knows for sure what it could consist of but there are more theories emerging as more observations are made. Only recently has this idea been developed since it was discovered. Dark Matter is called such because it does not emit light, obviously making it difficult to see in the shadows of super luminous stars. What we do see is its gravitational force on the objects around it. This is most notable in the rotation of spiral galaxies. Based on the accepted laws of motion, the outer stars in a galaxy should move slower than those closer to the center. However, observations have shown that the galaxy rotates at a relatively consistent speed. This is a main theory for the presence of Dark Matter. Since it is moving there must be something acting on it that we are unable to see. It is thought to be made up of either matter that we know (baryonic aka protons neutrons and electrons) such as dim white dwarfs, brown dwarfs and neutron stars. A more likely scenario is that it is made up of matter that is unknown to us (non-baryonic) and of which we do not have a way of detecting. The graph below shows the calculated rotation of the galaxy compared to what was actually measured. This observation is reason enough to ask the questions and to find the cause for this anomaly.

 

http://oneminuteastronomer.com/8774/rotating-galaxies-2/

http://www.space.com/20930-dark-matter.html