9.9: The Sun- A Garden-Variety Star (Exercises)
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
- Describe the main differences between the composition of Earth and that of the Sun.
- 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.
- 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?
- Why do sunspots look dark?
- Which aspects of the Sun’s activity cycle have a period of about 11 years? Which vary during intervals of about 22 years?
- Summarize the evidence indicating that over several hundreds of years or more there have been variations in the level of the solar activity.
- What it the Zeeman effect and what does it tell us about the Sun?
- 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.
- Compare and contrast the four different types of solar activity above the photosphere.
- What are the two sources of particles coming from the Sun that cause space weather? How are they different?
- How does activity on the Sun affect human technology on Earth and in the rest of the solar system?
- How does activity on the Sun affect natural phenomena on Earth?
Thought Questions
- Table \(15.1.1\) indicates that the density of the Sun is 1.41 g/cm 3 . Since other materials, such as ice, have similar densities, how do you know that the Sun is not made of ice?
- Starting from the core of the Sun and going outward, the temperature decreases. Yet, above the photosphere, the temperature increases. How can this be?
- 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.
- 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.)
- 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?
- Why would a flare be observed in visible light, when they are so much brighter in X-ray and ultraviolet light?
- How can the prominences, which are so big and ‘float’ in the corona, stay gravitationally attached to the Sun while flares can escape?
- If you were concerned about space weather and wanted to avoid it, where would be the safest place on Earth for you to live?
- 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?