The Sun's life from start to finish

Grade 9 Science Worksheet

Circle the best answer.

1. 1.

   The Sun is 4.6 billion years into a 10-billion-year main sequence. About what percent has it used, by Bo's math?

   • About 100%, so it is nearly done
   • About 4.6%
   • About 46%
   • About 90%, so it ends soon
2. 2.

   On Jun's timeline, 1 m stands for 1 billion years. How far from the Sun's formation is now?

   • 0.46 m
   • 46 m
   • 4.6 m
   • 4.6 mm
3. 3.

   Hydrogen fusing into helium. Why will the Sun leave the main sequence, by Kira's reading (NASA)?

   • It will grow heavy enough to explode
   • It will run out of the oxygen it needs to burn
   • Its core will run out of hydrogen to fuse
   • Its fuel will run out, so it will go dark at once
4. 4.

   “Star card cutaway:” When the core runs out of hydrogen, gravity squeezes it. What happens next, by Luz's reading (NASA)?

   • The core heats up and the outer layers swell
   • The outer layers cool and shrink
   • The core explodes as a supernova
   • The whole Sun shrinks and goes completely dark
5. 5.

   “sources give 7 to 10” Why will the Sun not end as a supernova, by Milo's reading (NASA)?

   • It already exploded long ago
   • It will explode once it becomes a red giant
   • It has too little mass; only far heavier stars explode
   • It is too hot to explode
6. 6.

   The Sun today beside a red giant, with surface colors shown. Compared with the Sun today, how does a red giant's surface compare, by Noah's reading?

   • Cooler and redder, though the star is far brighter
   • Exactly the same
   • Hotter and whiter, since the star becomes so much bigger
   • Hotter and dimmer
7. 7.

   Drawing of a huge red giant beside a small yellow star. Why is a red giant so bright if its surface is cool, by Pia's reading?

   • It reflects light from nearby planets
   • Its surface is the hottest of any stage
   • Its huge surface area gives off a lot of light
   • Its surface is hotter than the Sun's is now
8. 8.

   What becomes of the Sun's outer layers at the end of its red giant stage, by Tala's reading (NASA)?

   • They drift away as a planetary nebula
   • They collapse into a black hole around the core
   • They explode in a supernova
   • They stay and keep fusing hydrogen
9. 9.

   Star card cutaway of a white dwarf. What fuses inside a white dwarf, by Zee's reading (NASA)?

   • Helium into carbon, as in a red giant
   • Carbon into iron
   • Nothing; it glows from stored heat as it cools
   • Hydrogen into helium
10. 10.

    Red giant core fusing helium into carbon, then the white dwarf left behind. Mostly what will the Sun's white dwarf be made of, by Ari's reading (NASA)?

    • Neutrons packed tightly together
    • Mostly hydrogen, as the Sun is now
    • Iron, from fusion up the periodic table
    • Mostly carbon, made by helium fusion