Sunspots and Climate

Students identify sunspots on images of the Sun, discovering that the number, location, and size of spots are not always the same. During the first part of the activity, students make a graph that shows how the number of sunspots has changed over the past 30 years, discovering that there is a regular pattern to the number of sunspots (the 11-year sunspot cycle). During the second part of the activity, students interpret a graph of sunspot data from the coldest part of the Little Ice Age (Maunder Minimum) to discover that the regular pattern of sunspots was disrupted in the past and this had an effect on the climate of our planet.

Learning Goal

Students will learn that when the temporal pattern of sunspots has been disrupted in the past, there has been climate change on Earth.

Learning Objectives

  • Students will understand that the Sun has features called sunspots.
  • Students will understand that the number and location of sunspots change over time.
  • Students will learn through graphing data that the number of sunspots varies over time with a regular pattern.

Materials

Copies for each student:

Student Pages (pages 1-2) Sunspots and Climate Activity

 

Preparation

  • Copy Student Page 1 (Graphing Sunspots) and Student Page 2 (Sunspots and Climate) for each student.
  • Familiarize yourself with the sunspot images (slide 2 of the slide deck)

Directions

Introducing the Lesson

This is four images of the Sun, all taken in 2005, that show the changing number and location of sunspots. The number of sunspots decreases throughout the year, with the first image from March showing the most sunspots, and the last image from August showing almost none.
  1. Tell students that they should never look directly at the Sun. (This can cause blindness.)
  2. Show students the images (below) of the Sun using the slide deck (slide 2). Describe how pictures like this are taken. (They are not photographs; the data is collected by a remote sensing instrument called MDI that is on the SOHO spacecraft and made into a representation or image that looks like a photograph.)
  3. Start with the upper left picture (A, courtesy of spaceweather.com). This shows a very large sunspot and quite a few smaller ones. To provide a sense of scale, there is a small dot to indicate the size of Earth as compared with the sunspots (point this out to students).
  4. Look at the other images on the slide (B-D) and see if members of the class can find sunspots. All three of these images show the Sun on different days of July 2005. The date and time are in the lower left of each image. (All three images courtesy of NASA SOHO.)
  5. Discuss the following as a class:
    • Do the number of spots stay the same? Brainstorm ideas about why the number of visible sunspots might change over time. There are two reasons why this might be: 1) we are not always looking at the same side of the Sun because the Sun rotates and Earth orbits, thus the number of spots we can see can vary with the time of day over a few days or weeks (example: compare images B-D); 2) the number of sunspots can change over weeks, months, years (example: compare image A with the others).
    • Are all the spots the same? Notice that some spots are large and others are small.
    • Tell students that scientists have been observing the number of spots on the sun for hundreds of years. In this lesson they will investigate this data to see if there is a pattern to the number of spots.

Facilitating the Lesson

  1. Pass out Student Page 1: Graphing Sunspot Data.
  2. Describe to students that listed in the data table on the student page is the average number of sunspots for each year. Scientists take the size and number of sunspots into account in their observations as well as the side of the Sun they can view and the technology used to collect the sunspot data.
  3. Have students graph the points and answer the interpretation questions at the bottom of the student page.
  4. Discuss the answers to the interpretation questions, especially the pattern of the sunspot numbers. Describe that the pattern they are seeing is called the Solar Cycle. This cycle also correlates with other types of phenomena such as solar storms and other changes in space weather.
  5. Next, tell students that they are going to examine a graph of sunspot data from 1630 to 1770. Ask students to predict the type of pattern they would expect to see in the number of sunspots, based on their knowledge of sunspots built during this lesson so far.
  6. Hand out Student Page 2: Sunspots and Climate and review the directions with the class. Discuss how to interpret a graph.
  7. After students have had a chance to work individually on their answers to the questions on the Student Page,,discuss answers as a group. Students have hopefully recognized that the climate cooled when there were few sunspots. This period of time (1645-1715) was called the Maunder Minimum. It was the coldest period of the Little Ice Age. (See Background Information)

Background

When viewed through a telescope, sunspots have a dark central region surrounded by a somewhat lighter region. The dark area is slightly cooler than the surrounding area. This cool area is likely related to a strong magnetic field around the sunspot. Sunspots typically last anywhere from a few days to a few months.

People have been observing and keeping records of sunspots for hundreds of years. In 1612, Galileo proved there were spots on the Sun. He used a telescope to look at the Sun (not directly!). At the time, telescopes (and other optics) were very recent innovations and were allowing scientists such as Galileo to discover new aspects of our planet and space. Galileo's discovery was highly controversial at the time because the spots he found were viewed as imperfections. Many of his 17th century colleagues did not believe the Sun could be imperfect!

This is a graph showing that sunspots peak and decline in a predictable 11 year pattern.

This graph of yearly sunspot numbers shows the repeating pattern of 11-year solar cycles.

Over time, scientists have noticed a pattern in the number of sunspots. About every 11 years, the number of sunspots reaches a high and then decreases again. This is known as the Solar Cycle. Other sorts of solar activity are related to this cycle as well, such as solar flares, which tend to occur on areas of the Sun near sunspots. The year 2011 will be a solar maximum, making 2006 and 2015 close to solar minimums.

When the Sun has fewer sunspots, it gives off less energy. This results in less energy making its way to Earth, and our planet cools. More than 300 years ago, when the climate was cooler for a time called the "Little Ice Age," people noticed there were no sunspots for several decades. This possible correlation between the number of sunspots and temperature is what students should find on the graph on Student Page 2.

Extensions

  • Take a look at sunspots WITHOUT LOOKING AT THE SUN! To do this safely, you will need to project an image of the Sun through either a pair of binoculars, a telescope, or a device called a Sunspotter onto a piece of white paper or a white wall. For more information about how to safely look at sunspots with your class, see the websites listed in the Related Resources section below.
  • Take a field trip to a local observatory, if possible.

Related Resources