The Sun's layers and the fusion that powers it

Grade 9 Science Worksheet

Circle the best answer.

1. 1.

   Energy has crossed the radiative zone and enters the next layer out. Which layer is that, and how does energy move there, by Esme's reading?

   • Photosphere: it escapes the core in 8 minutes
   • Photosphere: hot plasma rises, cools and sinks
   • Convection zone: energy moves as bouncing light
   • Convection zone: hot plasma rises, cools and sinks
2. 2.

   Drawing of a patch of the photosphere covered in bright granules with dark edges, with rising and sinking arrows beneath. Close-up images of the photosphere show granules: bright centers with darker edges. What are they, by Jun's reading?

   • Tops of the radiative zone, where light bounces
   • Tops of convection cells: hot plasma rising, cooler plasma sinking
   • Spots where fusion breaks through from the core
   • Small fires burning on the surface
3. 3.

   ? hydrogen-1 → 1 helium-4 + energy. In the Sun's core, how many hydrogen-1 nuclei end up in one helium-4 nucleus, by Kira's count?

   • 8
   • 1, by splitting helium
   • 2
   • 4

4. Read this first

   Masses (NIST, rounded)

   Particles	Mass (u)
   4 hydrogen-1 atoms	4.0313
   1 helium-4 atom	4.0026

5. 4.

   Using the same masses, about what percent of the hydrogen's mass becomes energy, by Milo's math?

   • 0%, since mass is conserved
   • About 0.7%
   • About 70%
   • About 7%
6. 5.

   The Sun is about 150 million km from Earth (NASA), and light travels about 300,000 km/s. How long does sunlight take to arrive, by Noah's math?

   • About 500 s, or 8.3 minutes
   • About 50,000 s, or 14 hours
   • About 5 s
   • About 170,000 years, since light starts in the core
7. 6.

   A path from the core to the photosphere labeled about 170,000 years, then to Earth labeled about 8 minutes. The sunlight Pia sees now left the photosphere about 8 minutes ago. About when was its energy released in the core (NASA)?

   • Just now
   • About 4.5 billion years ago, when the Sun formed
   • About 8 minutes ago
   • About 170,000 years ago, plus 8 minutes
8. 7.

   “not to scale” Mars is about 228 million km from the Sun (NASA). How long does sunlight take to reach Mars, at about 300,000 km/s, by Ren's math?

   • About 170,000 years
   • About 760 minutes
   • About 12.7 minutes
   • About 8.3 minutes, the same as Earth
9. 8.

   A blue main-sequence star sits up and to the left of the Sun on the H-R diagram. Compared with the Sun, it is what, by Tala's reading?

   • Hotter and brighter
   • The same, since both are on the main sequence
   • Cooler and dimmer
   • Cooler but brighter
10. 9.

    A red main-sequence star sits down and to the right of the Sun. Compared with the Sun, it is what, by Zee's reading?

    • Hotter but dimmer
    • Hotter and brighter
    • Cooler and dimmer
    • A star that fuses no hydrogen
11. 10.

    H-R diagram with the main sequence as a band and the Sun's dot on it. Why is the Sun's dot on the main sequence, by Ari's reading?

    • Its hot surface, not its core, makes the energy
    • It is burning fuel with oxygen
    • It is fusing hydrogen into helium in its core
    • It is splitting heavy atoms