Historical Sunspot Activity: Finding Patterns

A Carolina Essentials™ Activity

Total Time: 30-45 mins

Prep: 15 mins | Activity: 30-45 mins

Earth and Space Science


High School


When studying the Sun, students are often told that there is an 11-year sunspot cycle and that the cycle of maximum and minimum number of sunspots can affect our weather here on Earth. Scientists have been studying sunspots, their location, groupings, and motion for hundreds of years. At the same time every day, astronomers in Belgium still map the number and location of sunspots by hand to help forecast solar weather.


In this activity, students use historical data from SILSO, the Royal Observatory of Belgium, to plot the monthly average of sunspots over a 30-year period. From the plot, students determine if a cycle exists, and if one does, the length of the cycle.


The data set is large and can be broken up into sections for individual students or groups of students if graphing by hand. The entire plot can be constructed from each group’s part. The procedure is simple, but the data visualization is a powerful tool for establishing the sunspot cycle pattern.


Look at the photo of the sun disk. Circle the individual and group sunspots. How might the disk appear in 3 days?


The Sun. Sunspots visible on the surface.

Essential Question

How does the sunspot cycle contribute to a model explaining the release of energy by the Sun?

Activity Objectives

  1. Use monthly sunspot averages to determine if a sunspot cycle exists.
  2. If a sunspot cycle exists, determine the length of the cycle.

Next Generation Science Standards* (NGSS)

PE HS-ESS1-1. Develop a model based on evidence to illustrate the life span of the Sun and the role of nuclear fusion in the Sun’s core to release energy in the form of radiation.

Science & Engineering Practices

Developing and Using Models

Disciplinary Core Ideas

ESS1.A: The Universe and Its Stars

Crosscutting Concepts

Scale, Proportion, and Quantity


Safety Procedures and Precautions

No PPE is required for the activity.

Teacher Preparation and Disposal

Print or download the student activity sheets and the sunspot data table. Divide the data table into group segments if desired. No disposal of materials.

Student Procedures

  1. Your teacher will assign you a section of the data table or the entire data table to graph.
  2. Decide as a class the scale that should be used for the x-axis and y-axis.
  3. Graph the data assigned.
  4. Mark the maximum points on the plot with a colored vertical line.
  5. Using a different color, mark the minimum points on the plot with a vertical line.
  6. If you were assigned a section of the data table, join your section of the graph (or plot) to the others in chronological order to make a complete plot.

Teacher Preparation and Tips

  1. To save time, segment the data table if students are graphing by hand. Then, tape all the individual graphs together to make one large plot. Students can take a gallery walk to check maximums and minimums.

Data and Observations

Analysis & Discussion

  1. In the space below, construct a data table with the date of every maximum and minimum for the 30-year period.

    Students answers may vary slightly in the month selected. Stress the importance to your students of reading the graph and the maximum and minimum points they selected in the procedure.

  2. Calculate the time in years and months between maximums and minimums.

    The time should be between 5 and 6 years, half of the sunspot cycle.

  3. Calculate the time in years and months between every 2 maximums.

    The time should be about 11 years, a full sunspot cycle.

  4. Average the lengths of time between every 2 maximums shown on the full plot.

    The average time should be about 11 years.

  5. Explain whether a sunspot cycle exists using the data above.

    A sunspot cycle of about 11 years exists. There is a regular pattern of maximum sunspot activity and minimum sunspot activity.

  6. Explain how the presence of a sunspot cycle models the Sun’s production of energy.

    The Sun’s core produces energy through nuclear fusion. The heat or thermal energy produced by fusion is large enough that the surface of the Sun is about 5,800 K. Heat moves from the core, where fusion is taking place, to the surface by convection currents, keeping the surface hot enough to be in the plasma state where there is an abundance of charged particles.

    Magnetic fields are associated with convection of the hot plasma, and in places a strong magnetic field can cause cooling of around 2,000 K. These cooler places are visible as the darker spots we call sunspots. Therefore, sunspots model the transfer of heat from the core to the photosphere, and their movement over time indicates the motion of magnetic fields.

*Next Generation Science Standards® is a registered trademark of Achieve. Neither Achieve nor the lead states and partners that developed the Next Generation Science Standards were involved in the production of, and do not endorse, these products.

This website uses cookies to improve your experience. We'll assume you're ok with this, but you can opt-out if you wish. Accept Read More