_______________ clusters of galaxies contain closely spaced galaxies and often contain giant elliptical galaxies and a hot intergalactic medium.
Fill in the blank(s) with correct word
Question 2
As a star like the Sun exhausts hydrogen in its core, the outer layers of the star
a. become hotter and more luminous.
b. become cooler and more luminous.
c. become hotter and less luminous.
d. become cooler and less luminous.
e. become larger in radius and hotter.