The dark halo is now believed to extend at least
A) 100,000 light-years.
B) 50 kpc.
C) 8 kpc.
D) 15,000 light-years.
E) 15 kpc.
Question 2
How can Betelgeuse be only half the Sun's surface temperature, yet about 10,000 times more luminous than the hotter Sun?
What will be an ideal response?