Stars and Brightness — Answer Key
Part A: Multiple Choice
Circle the best answer for each question.
1. Star A and Star B give off the same actual light, but Star B is twice as far from Earth. How does Star B appear?
A) Dimmer than Star A from Earth's view
B) Exactly as bright as Star A always
C) Brighter than Star A from Earth's view
D) Completely invisible at any distance
Light spreads out with distance, so a more distant star of the same true brightness looks dimmer from Earth.
2. An observer near the North Pole is most likely to see which constellation high overhead all year?
A) The Southern Cross close to the southern horizon
B) Ursa Major and Polaris circling near the zenith
C) Constellations only visible south of the equator
D) No constellations because the sky stays empty
Near the North Pole, Polaris is overhead and circumpolar constellations like Ursa Major never set.
3. If a star moves three times farther away while emitting the same light, its apparent brightness becomes about how much of the original?
A) About three times the original brightness
B) Exactly equal to the original brightness
C) About one-ninth of the original brightness
D) Completely zero from any location
Tripling distance reduces apparent brightness by a factor of 3 squared, or 9, due to the inverse-square law.
4. An observer at the equator looks straight up on a clear night. What is most likely true of their view?
A) They cannot see any stars at the equator
B) Polaris appears directly overhead at all times
C) Only the Southern Cross is ever visible
D) They can see parts of both northern and southern skies through the year
Equatorial observers can view both northern and southern constellations as Earth orbits the Sun each year.
Part B: Fill in the Blank
Write the correct answer on each line.
1. The actual amount of light a star gives off is called its true brightness, not its apparent brightness.
True brightness, also called luminosity, measures the actual energy a star produces each second.
2. When a star is very far away, it usually looks dimmer than a closer star with the same true brightness.
The inverse-square law means apparent brightness decreases sharply as distance increases.
3. An observer at high northern latitudes will always see Polaris near the celestial north pole.
Polaris remains nearly fixed for northern observers because it lies close to Earth's rotational axis.
4. Observers in the Southern Hemisphere can never see Polaris because it stays below their horizon.
Polaris sits north of the celestial equator, so it never rises above the horizon south of the equator.
5. If a star is moved twice as far from Earth, its apparent brightness becomes about one-fourth of what it was.
Doubling distance reduces apparent brightness to 1 over 2 squared, which equals one-fourth.