Question

2. If star A and star B have the same apparent magnitude, then it must be true that

a. star A and star B are the distance from Earth.

b. star A and star B also have the same absolute magnitude.

c. star A and star B are of the same spectral type.

d. none of the above.

6. We can see from the H-R diagram that cool stars tend to be

a. bright

b . faint

c. large

d. distant

7. The luminosity of a star is an indication of its

a. temperature

b. size

c. both a and b.

d. none of the above.

Answer 1

2. The apparent magnitude is the measure of the relative brightness of a star as seen from the Earth. A more luminous star may seem as bright as a less luminous star if the more luminous star is farther away from Earth than the less luminous star. If star A and star B have the same apparent magnitude, then they may be at different distances, may have different absolute magnitude and may have a different temperature(spectral class). Hence the answer is

d) none of the above

6 HR diagram plots luminosity vs temperature of the stars. We can see from the H-R diagram that cool stars tend to be

b . faint

7. According to Stefan Boltzmann law, the luminosity depends on both radius and temperature.

The luminosity of a star is an indication of its both temperature and size. Hence the answer is

c. both a and b.