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, photosphere, corona
   • Corona, core, photosphere
   • Photosphere, corona, core
   • Core, corona, photosphere
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?

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

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

   • 2
   • 8
   • 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.

   Four hydrogen-1 atoms have a mass of 4.0313 u; one helium-4 atom has 4.0026 u. What happens to the difference, by Luz's reading?

   • It burns away as smoke
   • Nothing; mass cannot change
   • It turns into extra hydrogen
   • It becomes energy (E = mc²)
8. 6.

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

   • 0%, since mass is conserved
   • About 70%
   • About 7%
   • About 0.7%
9. 7.

   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
10. 8.

    “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 8.3 minutes, the same as Earth
    • About 12.7 minutes
    • About 760 minutes
    • About 170,000 years
11. 9.

    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?

    • Cooler but brighter
    • The same, since both are on the main sequence
    • Cooler and dimmer
    • Hotter and brighter
12. 10.

    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
    • Hotter but dimmer
    • A star that fuses no hydrogen
    • Cooler and dimmer