Stars and Brightness — Answer Key
Part A: Multiple Choice
Circle the best answer for each question.
1. A light-year is best described as what?
A) The distance light travels in one year
B) How long a star lives in years
C) The age of the universe in years
D) How fast a planet orbits its star
A light-year is a distance unit equal to about 6 trillion miles, the path light travels in one Earth year.
2. If a star moves much closer to Earth, what happens to how bright it looks?
A) It looks the same brightness
B) It looks brighter from Earth
C) It disappears completely
D) It changes color but not brightness
Closer stars send more concentrated light to our eyes, so apparent brightness increases as distance decreases.
3. A red giant star is best described as which of these?
A) A small, hot, blue young star
B) A medium yellow star like our Sun
C) A huge, cool, reddish older star
D) A tiny dim star made of ice
Red giants are aging stars that have swelled to enormous sizes and cooled, glowing with a reddish color.
4. Which famous star is known as the North Star and stays nearly fixed above Earth's North Pole?
A) Sirius
B) Betelgeuse
C) Rigel
D) Polaris
Polaris sits almost exactly above Earth's North Pole, so it appears nearly motionless while other stars seem to circle.
Part B: Fill in the Blank
Write the correct answer on each line.
1. A white dwarf is a small, hot, very dense star left after a Sun-like star dies.
White dwarfs form when stars like our Sun shed outer layers, leaving a hot, Earth-sized core behind.
2. If a star moves farther from Earth, its apparent brightness will decrease.
Light spreads out as it travels, so a star's light becomes weaker and dimmer when it is farther from Earth.
3. Light from the closest star besides the Sun takes about four years to reach Earth.
Proxima Centauri is about 4.2 light-years away, so its light takes around four years to reach our planet.
4. The supergiant star Betelgeuse, in Orion's shoulder, is huge and reddish.
Betelgeuse is a red supergiant about 700 times wider than the Sun and a key star in the Orion constellation.
5. Even though a light-year sounds like time, it actually measures distance.
A light-year measures distance: the path light covers in one Earth year, used to describe space distances.