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9.9: The Sun- A Garden-Variety Star (Exercises)

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    For Further Exploration

    Articles

    Berman, B. “How Solar Storms Could Shut Down Earth.” Astronomy (September 2013): 22. Up-to-date review of how events on the Sun can hurt our civilization.

    Frank, A. “Blowin’ in the Solar Wind.” Astronomy (October 1998): 60. On results from the SOHO spacecraft.

    Holman, G. “The Mysterious Origins of Solar Flares.” Scientific American (April 2006): 38. New ideas involving magnetic reconnection and new observations of flares.

    James, C. “Solar Forecast: Storm Ahead.” Sky & Telescope (July 2007): 24. Nice review on the effects of the Sun’s outbursts and on Earth and how we monitor “space weather.”

    Schaefer, B. “Sunspots That Changed the World.” Sky & Telescope (April 1997): 34. Historical events connected with sunspots and solar activity.

    Schrijver, C. and Title, A. “Today’s Science of the Sun.” Sky & Telescope (February 2001): 34; (March 2001): 34. Excellent reviews of recent results about the solar atmosphere.

    Wadhwa, M. “Order from Chaos: Genesis Samples the Solar Wind.” Astronomy (October 2013): 54. On a satellite that returned samples of the Sun’s wind.

    Websites

    Dr. Sten Odenwald’s “Solar Storms” site: http://www.solarstorms.org/.

    ESA/NASA’s Solar & Heliospheric Observatory: http://sohowww.nascom.nasa.gov. A satellite mission with a rich website to explore.

    High Altitude Observatory Introduction to the Sun: www.hao.ucar.edu/education/basic.php. For beginners.

    NASA’s Solar Missions: https://www.nasa.gov/mission_pages/s...ons/index.html. Good summary of the many satellites and missions NASA has.

    NOAA Profile of Space Weather: www.swpc.noaa.gov/sites/defau...r_2010_new.pdf. A primer.

    NOAA Space Weather Prediction Center Information Pages: www.swpc.noaa.gov/content/edu...n-and-outreach. Includes primers, videos, a curriculum and training modules.

    Nova Sun Lab: http://www.pbs.org/wgbh/nova/labs/lab/sun/. Videos, scientist profiles, a research challenge related to the active Sun from the PBS science program.

    Space Weather: Storms on the Sun: www.swpc.noaa.gov/sites/defau...wx_booklet.pdf. An illustrated booklet from NOAA.

    Stanford Solar Center: http://solar-center.stanford.edu/. An excellent site with information for students and teachers.

    Apps

    These can tell you and your students more about what’s happening on the Sun in real time.

    NASA Space Weather: itunes.apple.com/us/app/nasa...422621403?mt=8.

    Solaris Alpha: play.google.com/store/apps/d...y.solarisalpha.

    Solar Monitor Pro: www.solarmonitor.eu/.

    Videos

    Journey into the Sun: https://www.youtube.com/watch?v=fqKFQ7z0Nuk. 2010 KQED Quest TV Program mostly about the Solar Dynamics Observatory spacecraft, its launch and capabilities, but with good general information on how the Sun works (12:24).

    NASA | SDO: Three Years in Three Minutes--With Expert Commentary: https://www.youtube.com/watch?v=QaCG0wAjJSY&src. Video of 3 years of observations of the Sun by the Solar Dynamics Observatory made into a speeded up movie, with commentary by solar physicist Alex Young (5:03).

    Our Explosive Sun: http://www.youtube.com/watch?v=kI6YGSIJqrE. Video of a 2011 public lecture in the Silicon Valley Astronomy Lecture Series by Dr. Thomas Berger about solar activity and recent satellite missions to observe and understand it (1:20:22).

    Out There Raining Fire: www.nytimes.com/video/science....html?emc=eta1. Nice overview and introduction to the Sun by science reporter Dennis Overbye of the NY Times (2:28)

    Space Weather Impacts: www.swpc.noaa.gov/content/edu...n-and-outreach. Video from NOAA (2:47); https://www.youtube.com/playlist?lis...bIUzBO6JI0Pvx0. Videos from the National Weather Service (four short videos) (14:41).

    Space Weather: Storms on the Sun: http://www.youtube.com/watch?v=vWsmp4o-qVg. Science bulletin from the American Museum of Natural History, giving the background to what happens on the Sun to cause space weather (6:10).

    Sun Storms: www.livescience.com/11754-sun...nic-world.html. From the Starry Night company about storms from the Sun now and in the past (4:49).

    Sunspot Group AR 2339 Crosses the Sun: http://apod.nasa.gov/apod/ap150629.html. Short video (with music) animates Solar Dynamics Observatory images of an especially large sunspot group going across the Sun’s face (1:15).

    What Happens on the Sun Doesn’t Stay on the Sun: https://www.youtube.com/watch?v=bg_gD2-ujCk. From the National Oceanic and Atmospheric Administration: introduction to the Sun, space weather, its effects, and how we monitor it (4:56).

    Review Questions

    1. Describe the main differences between the composition of Earth and that of the Sun.
    2. Describe how energy makes its way from the nuclear core of the Sun to the atmosphere. Include the name of each layer and how energy moves through the layer.
    3. Make a sketch of the Sun’s atmosphere showing the locations of the photosphere, chromosphere, and corona. What is the approximate temperature of each of these regions?
    4. Why do sunspots look dark?
    5. Which aspects of the Sun’s activity cycle have a period of about 11 years? Which vary during intervals of about 22 years?
    6. Summarize the evidence indicating that over several hundreds of years or more there have been variations in the level of the solar activity.
    7. What it the Zeeman effect and what does it tell us about the Sun?
    8. Explain how the theory of the Sun’s dynamo results in an average 22-year solar activity cycle. Include the location and mechanism for the dynamo.
    9. Compare and contrast the four different types of solar activity above the photosphere.
    10. What are the two sources of particles coming from the Sun that cause space weather? How are they different?
    11. How does activity on the Sun affect human technology on Earth and in the rest of the solar system?
    12. How does activity on the Sun affect natural phenomena on Earth?

    Thought Questions

    1. Table \(15.1.1\) indicates that the density of the Sun is 1.41 g/cm3. Since other materials, such as ice, have similar densities, how do you know that the Sun is not made of ice?
    2. Starting from the core of the Sun and going outward, the temperature decreases. Yet, above the photosphere, the temperature increases. How can this be?
    3. Since the rotation period of the Sun can be determined by observing the apparent motions of sunspots, a correction must be made for the orbital motion of Earth. Explain what the correction is and how it arises. Making some sketches may help answer this question.
    4. Suppose an (extremely hypothetical) elongated sunspot forms that extends from a latitude of 30° to a latitude of 40° along a fixed of longitude on the Sun. How will the appearance of that sunspot change as the Sun rotates? (Figure \(15.2.5\) should help you figure this out.)
    5. The text explains that plages are found near sunspots, but Figure \(15.2.6\) shows that they appear even in areas without sunspots. What might be the explanation for this?
    6. Why would a flare be observed in visible light, when they are so much brighter in X-ray and ultraviolet light?
    7. How can the prominences, which are so big and ‘float’ in the corona, stay gravitationally attached to the Sun while flares can escape?
    8. If you were concerned about space weather and wanted to avoid it, where would be the safest place on Earth for you to live?
    9. Suppose you live in northern Canada and an extremely strong flare is reported on the Sun. What precautions might you take? What might be a positive result?

     

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