Question

What does the equivalent of an H-R diagram for galaxies, plotting luminosity versus color, show?

A) galaxies fill the diagram showing that there is no correlation between luminosity and color
B) two clumps, one blue with relatively low luminosity, one red with relatively high luminosity, and a valley in between with few galaxies
C) a continuum from faint, blue galaxies to bright, red galaxies
D) a continuum from faint, red galaxies to bright, blue galaxies
E) A main sequence, just as for stars

Answer 1

The H-R diagram equivalent for galaxies shows C. a continuum from faint, blue galaxies to bright, red galaxies, reflecting the presence of younger, hot stars in the former and older, cooler stars in the latter.

Step-by-step explanation:

The equivalent of an H-R diagram for galaxies, plotting luminosity versus color, shows a continuum from faint, blue galaxies to bright, red galaxies. This is because galaxy color indicates the types of stars that dominate the light we see. Faint, blue galaxies are actively forming new stars, which are massive and hot, contributing to their blue color. Conversely, bright, red galaxies mainly contain older, cooler stars, leading to a redder appearance. These trends correspond to the ages of the galaxies and their stellar populations.

The equivalent of an H-R diagram for galaxies, plotting luminosity versus color, shows a continuum from faint, blue galaxies to bright, red galaxies. This means that there is a correlation between luminosity and color for galaxies, with the brighter galaxies tending to be redder in color and the fainter galaxies tending to be bluer in color.