How does the sun produce energy?

1. The sun gives off tremendous amounts of energy. Plants on Earth use sunlight directly in photosynthesis.

2. How does the sun produce energy? The sun’s energy is produced in its central region by the fusion of hydrogen nuclei into helium nuclei. Energy From the Sun

3. Energy From the Sun The sun gives off tremendous amounts of energy in the form of electromagnetic radiation. In the early 1900s, scientists discovered the source of the sun’s energy—nuclear fusion in its central region. In the process of fusion, less massive nuclei combine into more massive nuclei, releasing enormous amounts of energy.

4. Energy From the Sun Nuclear fusion within the sun’s central region converts mass into energy. The green particles in the diagram are protons, and the purple particles are neutrons. Hydrogen nuclei collide to form helium-3 Gamma ray

5. Energy From the Sun Nuclear fusion within the sun’s central region converts mass into energy. The green particles in the diagram are protons, and the purple particles are neutrons. Hydrogen nuclei collide to form helium-3 Two helium-3 nuclei collide. Gamma ray

6. Energy From the Sun Nuclear fusion within the sun’s central region converts mass into energy. The green particles in the diagram are protons, and the purple particles are neutrons. Hydrogen nuclei collide to form helium-3 Two helium-3 nuclei collide. Helium-4 and hydrogen nuclei form. Gamma ray

7. Why does the sun remain stable over time? The sun remains stable because the inward pull of gravity balances the outward push of thermal pressure from nuclear fusion. Forces in Balance

8. Forces in Balance The fossil record of life on Earth shows that the sun has been a fairly stable energy source for billions of years. Inward and outward forces within the sun must be balanced so that temperature, pressure, and density at any depth remain fairly constant over time.

9. Forces in Balance The energy from nuclear fusion in the center of the sun causes ions to move faster, exerting an outward thermal pressure. At the same time, gravity pulls the gas inward. The sun will remain stable as long as there is a steady energy source within it. Astronomers estimate that the sun will remain stable for another 5 billion years.

10. Forces in Balance Gravity and the outward thermal pressure from nuclear fusion are balanced throughout the sun.

11. What is the structure of the sun? The sun’s interior consists of the core, the radiation zone, and the convection zone. The Sun’s Interior

12. The Sun’s Interior Astronomers infer the structure of the sun’s interior using mathematical models, and they observations of vibrations of the sun that are similar to vibrations caused by earthquakes on Earth. The sun’s interior and atmosphere are divided into several layers with distinct characteristics.

13. The Sun’s Interior Core The sun’s core is its central region, where nuclear fusion occurs. The core has a diameter of about 400,000 kilometers, a little more than a quarter of the diameter of the entire sun.

14. The Sun’s Interior Radiation Zone You are able to see the sun because some of the energy produced in its core travels outward and escapes into space as visible light. The radiation zone is a region of highly compressed gas. Energy is transferred by the absorption and reradiation of electromagnetic waves. Because this region is so dense, energy can take more than 100,000 years to pass through it.

15. The Sun’s Interior Convection Zone Energy from the radiation zone passes into the convection zone, the outer layer of the sun’s interior. In the convection zone, energy is transferred outward mainly by convection currents. Hot gases in the convection zone rise toward the sun’s atmosphere while cooler gases sink downward.

16. The Sun’s Interior The sun has an interior and an atmosphere. Convection zone (about 200,000 km thick) Prominence Radiation zone(about 300,000 km thick) Chromosphere (about 1500 km thick) Corona (extending millions of km into space) Core(about 400,000 km in diameter) Photosphere (visible surface) Solar flare Granulated surface (caused by convection) Sunspot(cool region)

17. What is the structure of the sun? The sun’s atmosphere consists of three layers: the photosphere, the chromosphere, and the corona. The Sun’s Atmosphere

18. The Sun’s Atmosphere Photosphere The innermost layer of the sun’s atmosphere, which is the visible surface of the sun, is the photosphere. • The photosphere is about 500 kilometers thick and has an average temperature of about 5800 K. • The photosphere is called the sun’s surface. • The photosphere’s surface has a bubbly appearance. The bubbles, called granules, are the tops of convection currents.

19. The Sun’s Atmosphere Chromosphere In the chromosphere, the middle layer of the sun’s atmosphere, temperature increases to nearly 10,000 K. At these temperatures, hydrogen gas emits a reddish light. The faint chromosphere is normally visible only when the brighter photosphere is blocked, such as during a total solar eclipse.

20. The Sun’s Atmosphere Corona The chromosphere merges with the corona, the outermost layer of the sun’s atmosphere. • Gases in the corona are very hot, about 1 million Kelvin. • But the corona has such a low density that the total amount of thermal energy in it is relatively small.

21. The Sun’s Atmosphere • The corona extends millions of kilometers above the chromosphere. • The corona gradually thins into the solar wind, a stream of electrically charged particles that flows outward from the sun through the solar system.

22. The Sun’s Atmosphere The corona can only be seen from Earth during a total solar eclipse or when viewed with a special telescope.

23. What are some features of the sun’s atmosphere? Features of the sun’s atmosphere include sunspots, prominences, and solar flares. Features of the Sun’s Atmosphere

24. Features of the Sun’s Atmosphere Sunspots Sunspots are areas of gas in the photosphere that are cooler than the surrounding gases. Some sunspots are larger than Earth. If sunspots could be seen apart from the rest of the sun, they would shine brightly. Sunspots are often found in groups and are associated with intense magnetic fields on the sun.

25. Features of the Sun’s Atmosphere Sunspots last from a few hours to a few months. The number of sunspots varies in cycles, with about 11 years separating one sunspot peak from the next. During peak periods, there may be a hundred sunspots on the sun.

26. Features of the Sun’s Atmosphere Sunspots are relatively cool areas on the sun’s surface.

27. Features of the Sun’s Atmosphere The Italian scientist Galileo Galilei discovered that the sun rotates by observing the motion of sunspots. Sunspots near the sun’s equator move faster than sunspots near the sun’s poles. This means that the sun rotates faster at its equator than near its poles.

28. Features of the Sun’s Atmosphere Prominences Prominences are huge loops of gas that erupt from sunspot regions. They extend upward from the photosphere into the chromosphere and sometimes into the corona. Some prominences reach heights of more than 100,000 kilometers above the sun’s surface. Prominences travel along the magnetic field lines that connect sunspots.

29. Features of the Sun’s Atmosphere • This prominence forms a huge twirling loop connecting sunspot regions.

30. Features of the Sun’s Atmosphere • This prominence forms a huge twirling loop connecting sunspot regions. • A solar flare erupts on the edge of the sun.

31. Features of the Sun’s Atmosphere Solar Flares The sun’s surface sometimes erupts dramatically, producing X-rays and hurling charged particles into space at speeds of 1000 km/s or more in a solar flare. Solar flares usually occur near sunspots and heat the corona to a temperature near 20 million K. Solar flares increase the solar wind, so they can disrupt electric power transmission and radio, television, and telephone signals.

32. Assessment Questions • What is the source of the sun’s energy? • The friction between its molecules gives off thermal energy. • The conversion of potential energy into thermal energy as gravity pulls the sun into its own core. • Combustion of hydrogen gas on the sun’s surface. • Fusion of hydrogen nuclei into helium nuclei.

33. Assessment Questions • What is the source of the sun’s energy? • The friction between its molecules gives off thermal energy. • The conversion of potential energy into thermal energy as gravity pulls the sun into its own core. • Combustion of hydrogen gas on the sun’s surface. • Fusion of hydrogen nuclei into helium nuclei.ANS: D

34. Assessment Questions • The sun has remained stable for billions of years because there is a balance between • gravity and the tendency of hydrogen and helium to rise. • gravity and thermal pressure. • thermal pressure and the repulsion between nuclei. • the amount of energy it absorbs and the amount of energy it produces.

35. Assessment Questions • The sun has remained stable for billions of years because there is a balance between • gravity and the tendency of hydrogen and helium to rise. • gravity and thermal pressure. • thermal pressure and the repulsion between nuclei. • the amount of energy it absorbs and the amount of energy it produces.ANS: B

36. Assessment Questions • Convection currents in the sun’s convection zone carry energy from • the core to the photosphere. • the radiation zone to the photosphere. • the core to the radiation zone. • the photosphere to the corona.

37. Assessment Questions • Convection currents in the sun’s convection zone carry energy from • the core to the photosphere. • the radiation zone to the photosphere. • the core to the radiation zone. • the photosphere to the corona.ANS: B