Our galaxy is suspected to be surrounded by a galactic halo or corona because the disk of the galaxy
a. rotates faster than expected in its outer region.
b. rotates more slowly than expected in its outer region.
c. is only visible during a total eclipse of our Sun.
d. is surrounded above, below, and well beyond by the brightly glowing corona.
Question 2
How do the spectra of giants, supergiants, and main-sequence stars differ?
What will be an ideal response?