Sunspots: Cooler Surface Regions

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Author: Janice VanCleave

In the early 1600s in Paris, a German astronomer and Jesuit priest, Christoph Scheiner (1573–1650), was convinced he saw dark spots on the Sun. He was criticized for that idea because the renowned Greek philosopher Aristotle (384–322 B.C.) had stated that everything in the universe except Earth was perfect and without flaws. Scheiner revised his opinion and stated that the spots were caused by something near but not on the Sun. However, Galileo (1564–1642), an Italian scientist, saw the sunspots, studied their motion, and argued that they originated on the Sun. He is often credited as the first to discover them.

In this project, you will investigate the layers of the Sun. You will discover the photosphere, the area that appears to be the Sun's surface. You will observe the movement of sunspots to confirm that the Sun rotates. You will also learn how sunspots cycle and how they affect the Sun's activity.

Getting Started

Purpose: To build a model of the Sun's internal structure.


      serrated knife (use with adult approval)
      Styrofoam ball, 6 inches (15 cm) in diameter or larger
      2 different colored permanent markers
      four 1-by-4-inch (2.5-by-10-cm) white labels
      4 round toothpicks


  1. Use the knife to cut away one-fourth of the Styrofoam ball. Set the ball aside.
  2. With one of the markers, paint an area in the center of the ball to represent the Sun's core.
  3. Use the second marker to draw a band surrounding the core to represent the convection zone.
  4. Prepare four flags using these steps:
    • Touch the two sticky ends of a label together, leaving a gap near the folded end.
    • Insert a toothpick through the gap and press the label on the toothpick to make a flag (see Figure 7.1).
    • Sunspots Cooler Surface Regions

    • Write the names of the Sun's layers on the flags: Photosphere, Convection Zone, Radiation Zone, Core.
  5. Stick the flags in the Sun model as shown in Figure 7.2.
  6. Make a Layers of the Sun table like Table 7.1, showing the thickness and temperature of each layer.


You have made a model showing the layers of the Sun and a table describing some of their characteristics.

Sunspots Cooler Surface Regions


The Sun's core (center of a celestial body) is its hottest part. In the core, nuclear fusion (the combining of the nuclei of atoms) releases enormous amounts of radiation (energy that is transferred by electromagnetic waves, which have both magnetic and electrical properties). Energy from the hot core moves through the area outside the core called the radiation zone. From there, gases expand and rise. When they cool, they become denser and sink back down again. Circulating gas forms the convection zone. The next layer, the photosphere, is actually the first layer of the Sun's atmosphere. But from Earth, it looks like the Sun's surface. Your model does not show the layers of the atmosphere above the photosphere: the chromosphere and the outermost layer, the corona.

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