Chapter 29 Section 1

1. Chapter 29 Section 1 The Sun

2. The Sun contains most of the mass of the solar system and has many features typical of other stars.

3. I. Properties of the Sun • More than 99 percent of all the mass in the solar system • The Sun’s mass controls the motions of the planets and other objects

4. C. Density is similar to gas giant planets D. Computer models show that the density in the center of the Sun is about 1.50 × 105 kg/m3 (13x density of lead)

5. The Sun’s interior is gaseous throughout because of its high temperature— about 1 × 107 K (17,999,540.6 ºF) in the center. At this temperature, all of the gases are completely ionized. This means that the interior is composed only of atomic nuclei and electrons, in the state of matter known as plasma.

6. Section 29.1 The Sun

7. II. The Sun’s Atmosphere The outer regions of the Sun’s atmosphere are organized into layers, like a planetary atmosphere separated into different levels, and each layer emits energy at wavelengths resulting from its temperature.

8. A. Photosphere • Innermost layer of the Sun’s atmosphere (visible surface) • Average temperature of 5800 K (9980.6 ºF) • 400 km thick

9. B. Chromosphere • Visible only during a solar eclipse • Appears red Filter enhanced

10. C. Corona 1. Outer atmosphere 2. Invisible 3. Temperature range of 1 million to 2 million K (1,799,540.6 – 3,599,540.6 ºF) 4. Extends several million kilometers

11. D. Solar wind – gas flow outward from corona • Charged particles, called ions • Deflected by Earth’s magnetic field • Trapped in the Van Allen belts • Collide with Earth’s atmosphere • a. Aurora

12. III. Solar Activity A. Sunspots • Dark, cool spots on the surface • a. Last approx. two months • b. Occur in pairs • Number changes regularly • a. Maximum number every 11.2 yrs.

13. Current prediction for the next sunspot cycle maximum gives a smoothed sunspot number maximum of about 62 in July of 2013. We are currently over two years into Cycle 24. The predicted size would make this the smallest sunspot cycle in nearly 200 years.

14. B. Coronal holes 1. Often located over sunspot groups 2. Low density 3. Regions from which the particles that comprise the solar wind escape

15. D. Solar flares - violent eruptions of particles and radiation from the surface of the Sun. Highly active solar flares are associated with sunspots.

16. E. Prominence is an arc of gas ejected from the chromosphere, or gas that condenses in the Sun’s inner corona and rains back to the surface. Prominences can reach temperatures over 50,000 K and are associated with sunspots.

20. Mauna Loa Observatory

21. IV. The Solar Interior Fusion is the combination of lightweight atomic nuclei into heavier nuclei, such as hydrogen fusing into helium. This is the opposite of the process of fission, which is the splitting of heavy atomic nuclei into smaller, lighter nuclei, like uranium into lead.

22. A. Energy Production in the Sun 1. Nuclear fusion - E = mc2 a. E = energy b. m = mass c. c = speed of light 2. Two or more nuclei join a. Mass is lost b. Releases energy

24. B. Energy transport Energy in the Sun is transferred mostly by radiation from the core outward to about 86 percent of its radius. The outer layers transfer energy in convection currents. Fig. 29.6 page 834

25. As energy in the Sun moves outward, the temperature is reduced from a central value of about 1 × 107 K (17,999,540.6 ºF) to its photospheric value of about 5800 K (9980.6 ºF). A tiny fraction of the immense amount of solar eventually reaches Earth.

26. C. Solar energy on Earth • Above Earth’s atmosphere • a. 1354 J per square meter every second • b. Enough energy to operate thirteen 100-W lightbulbs • 2. Not all reaches the ground • a. Absorbed and scattered by the atmosphere

27. V. Spectra • Spectrum (plural, spectra) is visible light arranged according to wavelengths. • Three types of spectra: continuous, emission, and absorption.

28. A spectrum that has no breaks in it, such as the one produced when light from an ordinary bulb is shined through a prism, is called a continuous spectrum. A continuous spectrum can also be produced by a glowing solid or liquid, or by a highly compressed, glowing gas.

29. Emission Spectrum - noncompressed gas contains bright lines at certain wavelengths. The wavelengths of the visible lines depend on the element being observed because each element has its own characteristic emission spectrum.

30. Section 29.1 A spectrum produced from the Sun’s light shows a series of dark bands. These dark spectral lines are caused by different chemical elements that absorb light at specific wavelengths. This is called an absorption spectrum, and the lines are called absorption lines. The Sun

31. VI. Solar Composition Using the lines of the absorption spectra like fingerprints, astronomers have identified the elements that compose the Sun. The Sun is composed primarily of hydrogen and helium with small amounts of other gases. Fig. 29.8 page 836

32. The Sun’s composition represents that of the galaxy as a whole. Most stars have proportions of the elements similar to the Sun.

33. What causes the dark bands in a star’s spectrum? Answer: The various chemical elements that make up the star absorb light at specific wavelengths. This causes dark bands to appear in the star’s spectrum.

34. The Sun contains most of the mass of the solar system and has many features typical of other stars. • Most of the mass in the solar system is found in the Sun. • The Sun’s average density is approximately equal to that of the gas giant planets.

35. The Sun has a layered atmosphere. • The Sun’s magnetic field causes sunspots and other solar activity. • The fusion of hydrogen into helium provides the Sun’s energy and composition. • The different temperatures of the Sun’s outer layers produce different spectra.