Stars and Brightness — Answer Key
Part A: Fill in the Blank
Write the missing word or number on each line.
1. How bright a star looks from Earth is called its apparent brightness.
Apparent brightness is what we see from Earth, while actual brightness measures how much light a star truly emits.
2. A star can look brighter because it is closer or because it is bigger.
Bigger stars have more burning gas, so they emit more light and can outshine smaller, nearby stars.
3. The hottest stars usually glow with a blue color.
Blue stars are the hottest, with surface temperatures over twenty thousand degrees, far hotter than our Sun.
4. Our Sun is a medium-temperature star that glows yellow.
The Sun's surface is about ten thousand degrees, putting it in the yellow color group of stars.
5. The coolest visible stars look red in color.
Red stars have lower surface temperatures and emit more red light than hotter blue or white stars.
6. A pattern of stars that forms a picture in the sky is called a constellation.
Constellations are imaginary pictures that ancient people drew by connecting bright stars in the night sky.
7. Two stars can give off the same light, but the farther one looks dimmer from Earth.
Light spreads out as it travels, so a more distant star delivers less light to our eyes than a closer one.
8. The actual amount of light a star produces is its actual brightness.
Actual brightness, also called luminosity, is the real light output of a star, no matter how far away it is.
9. Stars appear to move across the night sky because Earth rotates.
As Earth spins, our view of the sky shifts, making stars appear to slowly travel from east to west.
Part B: Matching
Match each item on the left to the correct answer on the right.
1. Match each item to its correct answer.
Blue star
→ Hottest surface temperature
Hottest surface temperature
Yellow star
→ Medium temperature like the Sun
Medium temperature like the Sun
Red star
→ Coolest of visible stars
Coolest of visible stars
Constellation
→ Pattern of stars forming a picture
Pattern of stars forming a picture
Star color tells us temperature: blue is hottest, yellow is medium, red is coolest. Constellations are sky pictures.