Stars and Brightness — Answer Key
Part A: Multiple Choice
Circle the best answer for each question.
1. Why might a giant star far away look dimmer than a small star nearby?
A) Because distance makes light spread out and weaken
B) Because giant stars do not produce much light
C) Because small stars are always hotter than giants
D) Because Earth's atmosphere blocks giant stars only
Light spreads out with distance, so even a giant star's light may reach us weaker than a closer small star's light.
2. Two stars produce equal light. Star A is 5 light-years away, and Star B is 50 light-years away. Which appears brighter from Earth?
A) Star B because it is older
B) Star A because it is closer to Earth
C) They look exactly equal in brightness
D) Neither one can be seen from Earth
Apparent brightness depends on distance. Star A is closer, so its light reaches Earth more concentrated and bright.
3. Which star color group has the highest surface temperatures?
A) Red stars
B) Orange stars
C) Blue stars
D) Yellow stars
Blue stars have surface temperatures above twenty thousand degrees, making them the hottest visible color group.
4. Why does Polaris appear to stay nearly still in the night sky as Earth rotates?
A) It moves with Earth at the same speed
B) It only shines at night, never moving
C) It is the largest star known
D) It sits almost above Earth's North Pole
Polaris lines up nearly with Earth's rotation axis, so it appears fixed while stars near it seem to circle around.
Part B: Fill in the Blank
Write the correct answer on each line.
1. Sirius looks bright partly because it is only about 8.6 light-years from Earth.
Sirius is one of the closest stars to Earth, so its strong light gives it the brightest apparent brightness at night.
2. When a Sun-like star runs out of fuel, it can swell into a red giant.
As Sun-like stars age, their outer layers expand and cool, creating reddish giants before the star finally dies.
3. Astronomers measure the huge distances between stars using light-years.
Light-years are useful because miles and kilometers become impractical numbers when describing star distances.
4. A star's true light output, no matter where viewers are, is called its luminosity.
Luminosity is the total energy a star emits each second and does not depend on the observer's distance from it.
5. Compared to a red giant, a white dwarf is much smaller in size.
White dwarfs are about Earth-sized, while red giants can be hundreds of times wider than our entire Sun.