The figure below shows how the space density of a particular astronomical object depends on cosmic time.What kind of object does it show?
A) spiral galaxies
B) heavy elements
C) quasars
D) stars

Question

The figure below shows how the space density of a particular astronomical object depends on cosmic time.What kind of object does it show? 
A) spiral galaxies 
B) heavy elements 
C) quasars 
D) stars

Quizplus · Accepted Answer

The graph shows a peak in space density at around 2-3 billion years after the Big Bang and then a decline in density afterwards. This is characteristic of quasars, which are believed to be active galactic nuclei powered by supermassive black holes. The peak in density corresponds to a time when many galaxies were actively forming and merging, leading to increased activity in the nuclei of these galaxies and the formation of quasars. The decline in density afterwards could be due to the depletion of gas and dust in the region surrounding these supermassive black holes, leading to a decrease in their activity.

The Figure Below Shows How the Space Density of a Particular