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?

   • Corona, core, photosphere
   • Core, corona, photosphere
   • Photosphere, corona, core
   • Core, photosphere, corona
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: it escapes the core in 8 minutes
   • Photosphere: hot plasma rises, cools and sinks
   • Convection zone: 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?

   • Small fires burning on the surface
   • 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
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?

   • 4
   • 8
   • 2
   • 1, by splitting helium
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 170,000 years, since light starts in the core
   • About 5 s
   • About 500 s, or 8.3 minutes
   • About 50,000 s, or 14 hours
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)?

   • About 8 minutes ago
   • About 4.5 billion years ago, when the Sun formed
   • About 170,000 years ago, plus 8 minutes
   • Just now
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 8.3 minutes, the same as Earth
   • About 170,000 years
   • About 760 minutes
   • About 12.7 minutes
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 but brighter
   • Cooler and dimmer
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 and brighter
    • Hotter but dimmer
    • A star that fuses no hydrogen
    • Cooler and dimmer
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?

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