The Sun's layers and the fusion that powers it

Grade 9 Science Worksheet

Circle the best answer.

1. Read this first

   Sun temperatures (NASA)

   Layer	Temperature
   core	about 15 million °C
   corona	up to 2 million °C
   photosphere	about 5,500 °C

2. 1.

   NASA gives these temperatures: core about 15 million °C, corona up to 2 million °C, photosphere about 5,500 °C. Which order runs hottest to coolest, by Bo's reading?

   • Core, corona, photosphere
   • Core, photosphere, corona
   • Corona, core, photosphere
   • Photosphere, corona, core
3. 2.

   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: hot plasma rises, cools and sinks
   • Convection zone: energy moves as bouncing light
   • Convection zone: hot plasma rises, cools and sinks
   • Photosphere: it escapes the core in 8 minutes
4. 3.

   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?

   • Spots where fusion breaks through from the core
   • Small fires burning on the surface
   • Tops of convection cells: hot plasma rising, cooler plasma sinking
   • Tops of the radiative zone, where light bounces
5. 4.

   ? 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
   • 2
   • 4
   • 1, by splitting helium

6. Masses (NIST, rounded)

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

7. 5.

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

   • About 7%
   • About 0.7%
   • 0%, since mass is conserved
   • About 70%
8. 6.

   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 5 s
   • About 500 s, or 8.3 minutes
   • About 50,000 s, or 14 hours
   • About 170,000 years, since light starts in the core
9. 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 8.3 minutes, the same as Earth
   • About 760 minutes
   • About 12.7 minutes
10. 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
    • Cooler and dimmer
    • The same, since both are on the main sequence
    • Cooler but brighter
11. 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 and brighter
    • Cooler and dimmer
    • A star that fuses no hydrogen
    • Hotter but dimmer
12. 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?

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