Answer to Question #202928 in Astronomy | Astrophysics for Prachi

Question

Explain the need to postulate the existence of dark matter in the universe.

Answer 1

Dark matter is the name scientists have given to the particles which we believe exist in the universe, but which we cannot directly see! Dark matter was initially called "missing matter" because astronomers could not find it by observing the universe in any part of the electromagnetic spectrum. This material appears to have mass (and therefore generates gravity), but it does not appear to absorb or emit any electromagnetic radiation. Given the fact that it does not send us any light (which is how we have learned most of what we know about the universe), it is not difficult to understand that it has been hard to discover anything about the nature of these mysterious particles. But do not despair, scientists are coming up with clever new ways to probe the dark parts of the cosmos!

Scientists study dark matter by looking at the effects it has on visible objects. Scientists believe that dark matter may account for the unexplained motions of stars within galaxies. Computers play an important role in the search for dark matter information. They allow scientists to create models which predict galaxy behavior. Satellites are also being used to gather dark matterinformation. In 1997, a Hubble Space Telescope image revealed light from a distant galaxy cluster being bent by another cluster in the foreground of the image. Based on the way the light was bent, scientists estimated the mass of the foreground cluster to be 250 times greater than the visible matter in the cluster. Scientists believe that dark matter in the cluster accounts for the unexplained mass.