Question 1: Astronomers cannot directly measure the temperature of the central core of the Sun because:

a. we do not receive any radiation directly from the core.

b. black body laws fail at such high temperatures.

c. the central core is unstable.

d. the central core of the Sun is convective.

e. all of the hydrogen has been converted to helium.

Question 2: Hydrostatic equilibrium in the sun means that:

a. the electrical forces balance gas pressure.

b. the gravitational force balances the gas pressure.

c. the nuclear forces balance gravity.

d. the electrical forces balance the nuclear forces.

e. the electrical forces balance gravity.

Question 3: The photosphere is

a. the layer of the Sun in which most hydrogen fusion occurs.

b. the outermost layer of the Sun.

c. the layer of the Sun where the temperature is highest.

d. the layer of the Sun that we see when observing the Sun in visible light.

Question 4: The Sun derives its energy from

a. the conversion of hydrogen into energy.

b. the conversion of protons into energy.

c. chemical reactions that convert hydrogen into helium.

d. the fusion of hydrogen into helium.

e. a steady gravitational contraction of its core.

Question 4: The two most abundant elements in the Sun are

a. nitrogen and oxygen.

b. hydrogen and oxygen.

c. helium and lithium.

d. hydrogen and helium.

Question 5: When four hydrogen nuclei fuse to form a helium nucleus, the total electric charge at the end is _____ the total electric charge at the beginning.

a. more than

b. less than

c. the same as