Which single major problem perhaps concerns astronomers the most as they attempt to interpret the properties and behavior of clusters of galaxies?

Question

Quizplus · Accepted Answer

This is known as the "missing mass problem" or dark matter problem. It is a major concern for astronomers trying to understand the stability and behavior of galaxies and galaxy clusters. The fact that there appears to be much more mass present than can be accounted for by visible material suggests the existence of an unknown form of matter, which is still being studied and researched by scientists. The other options are also areas of interest and study, but not considered to be the single most concerning problem for astronomers.

Which Single Major Problem Perhaps Concerns Astronomers the Most as They