Stars and Brightness — Answer Key
Part A: Fill in the Blank
Write the missing word or number on each line.
1. Two main reasons a star looks bright from Earth are its size and its distance.
Closer stars deliver more concentrated light to Earth, so they appear brighter than equal stars far away.
2. A small but very close star can look brighter than a huge faraway star.
Light spreads out with distance, so even a small nearby star can outshine a giant star located far away.
3. Astronomers call the true light output of a star its luminosity.
Luminosity measures the total energy a star sends out each second, no matter how far away the observer is.
4. White stars are hotter than yellow stars but cooler than blue stars.
The color sequence from hottest to coolest is blue, white, yellow, orange, red, based on surface temperature.
5. Orion is a famous winter constellation shaped like a hunter with a belt.
Orion contains bright stars like Betelgeuse and Rigel and is visible in winter from the Northern Hemisphere.
6. The North Star, also called Polaris, sits almost directly above Earth's north pole.
Polaris stays nearly fixed above the North Pole, so travelers have used it to find direction for centuries.
7. Sirius is the brightest star in the night sky, partly because it is close to Earth.
Sirius, the Dog Star, is only about 8.6 light-years away, making it appear brighter than any other night star.
8. Two stars with the same actual brightness will look unequal if they are at different distances.
Apparent brightness depends on distance, so equal stars at different distances appear different from Earth.
9. Hotter stars give off more blue light than cooler stars do.
Hot stars peak in blue light, while cooler stars peak in red, which is why color reveals temperature.
Part B: Matching
Match each item on the left to the correct answer on the right.
1. Match each item to its correct answer.
Apparent brightness
→ How bright a star looks from Earth
How bright a star looks from Earth
Actual brightness
→ True light output of a star
True light output of a star
Polaris
→ North Star above Earth's pole
North Star above Earth's pole
Sirius
→ Brightest star in the night sky
Brightest star in the night sky
Apparent brightness is what we see, actual is true output, Polaris marks north, and Sirius is the brightest night star.