Happy Birthday Sunspot Plot - Sunspots and the Solar Cycle

Acknowledgements: Adapted from Happy Birthday Sunspot Plot, a NASA Thursday's Classroom activity. Background information includes excerpts from Sunspots and the Solar Cycle, sponsored by Science@NASA.

OBJECTIVES & UNDERSTANDINGS

After completing this activity, you should be able to:

MATERIALS

Each student will need a copy of the activity sheet and a pencil (to complete the graph).

BACKGROUND

What is "The Solar Cycle?" In a regular cycle, the Sun undergoes a period of great activity called the "solar maximum," followed by a period of quiet called the "solar minimum." One way scientists track solar activity is by observing sunspots. Sunspots are relatively cool areas that appear as dark blemishes on the face of the Sun. During solar maximum there are many sunspots; during solar minimum there are few.

Sunspot activity is monitored using an index called the "sunspot number." The sunspot number varies from day-to-day; daily sunspot numbers are averaged to derive an annual sunspot number. In this activity, you will explore the long-term cycle of solar activity by graphing the past 14 years of annual sunspot numbers.

Note: As a rule of thumb, if you divide the official sunspot number by 15, then you'll get the approximate number of individual sunspots visible on the solar disk if you look at the Sun by projecting its image on a white screen with a small telescope. [Caution: Never look directly at the Sun (especially through optical instruments such as telescopes) -- blindness may result!]

PROCEDURE

  1. Using the materials provided by your teacher, construct a bar graph of the annual sunspot number from 1986-1999.
  2. Answer the following activity questions.

ACTIVITY QUESTIONS

  1. Calculate the mean "average sunspot number" (annual sunspot number) for the past 14 years. How does this number compare with today's sunspot number (http://www.wsanford.com/~wsanford/exo/n-m_themes.html)?


  2. When (which year) was the last solar maximum? What was the annual sunspot number? Is the solar maximum a brief event, or does it tend to last for a period of months to years?


  3. When (which year) was the last solar minimum? What was the annual sunspot number?


  4. Assuming that the year 2000 turns out to be a solar maximum, how many years passed from the last solar maximum to the next (current) solar maximum? From such a relatively small data set, can the period of the solar cycle be determined with certainty?


  5. When (which year) were you born? Were you born during a solar maximum, solar minimum, or sometime in between? If the year 2000 turns out to be a solar maximum, then predict how old you will be during the next solar maximum.