Which single major problem perhaps puzzles astronomers MOST as they attempt to interpret the properties and behavior of clusters of galaxies?
A) rate of supernova occurrence in galaxies in some clusters
B) missing-mass problem, where the amount of mass needed for galactic cluster stability is estimated to be at least 10 times more than the observed visible mass
C) presence of star formation in many galaxies long after it is expected to have died out
D) structure and motion of spiral arms in galaxies in many clusters

Question

Quizplus · Accepted Answer

The missing-mass problem, or "dark matter" problem, is a major puzzle for astronomers because the gravitational effects observed in galaxy clusters suggest there is significantly more mass present than what we can see directly through telescopes. This discrepancy indicates that the majority of the mass in the universe is invisible to current detection methods, challenging our understanding of the universe's composition.

Which Single Major Problem Perhaps Puzzles Astronomers MOST as They