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, photosphere, corona
   • Core, corona, 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?

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

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

5. Masses (NIST, rounded)

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

6. 4.

   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?

   • Nothing; mass cannot change
   • It becomes energy (E = mc²)
   • It turns into extra hydrogen
   • It burns away as smoke
7. 5.

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

   • About 0.7%
   • About 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 170,000 years, since light starts in the core
   • About 50,000 s, or 14 hours
9. 7.

   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 170,000 years ago, plus 8 minutes
   • About 8 minutes ago
   • About 4.5 billion years ago, when the Sun formed
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 760 minutes
    • About 8.3 minutes, the same as Earth
    • About 12.7 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
    • Cooler and dimmer
    • Hotter and brighter
    • The same, since both are on the main sequence
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 but dimmer
    • Cooler and dimmer
    • Hotter and brighter
    • A star that fuses no hydrogen