4.1d Surface Features of the Sun

Is the sun always the same?

For most of human history, people thought the sun didn’t change much. But technology has offered us a window into the sun’s life. SOHO and other technologies allow us to observe incredible sunspots, flares, and prominences. Some of these are featured in this lesson.

Surface Features of the Sun

The sun has many incredible surface features. Don’t try to look at them, though! Looking directly at the sun can cause blindness. Find the appropriate filters for a pair of binoculars or a telescope and enjoy!


The most noticeable magnetic activity of the sun is the appearance of sunspots.Sunspots are cooler, darker areas on the sun’s surface ( Figure below ). Sunspots occur in an 11-year cycle. The number of sunspots begins at a minimum. The number gradually increases to the maximum. Then the number returns to a minimum again.

Sunspots form because loops of the sun’s magnetic field break through the surface. Sunspots usually occur in pairs. The loop breaks through the surface where it comes out of the sun. It breaks through again where it goes back into the sun. Sunspots disrupt the transfer of heat from the sun’s lower layers.

The darker regions in this image are sunspots.

Solar Flares

A loop of the sun’s magnetic field may break. This creates solar flares . Solar flares are violent explosions that release huge amounts of energy ( Figure below ). The streams of high energy particles they emit make up the solar wind . Solar wind is dangerous to spacecraft and astronauts. Solar flares can even cause damage on Earth. They have knocked out entire power grids and can disturb radio, satellite, and cell phone communications.

The solar flare is the bright area in the lower right.

Solar Prominences

Another amazing feature on the sun is solar prominences . Plasma flows along the loop that connects sunspots. This plasma forms a glowing arch. The arch is a solar prominence. Solar prominences can reach thousands of kilometers into the sun’s atmosphere. Prominences can last for a day to several months. Prominences can be seen during a total solar eclipse.

Solar Dynamics Observatory

NASA’s Solar Dynamics Observatory (SDO) was launched on February 11, 2010. SDO is studying the sun’s magnetic field. This includes how the Sun affects Earth’s atmosphere and climate. SDO provides extremely high resolution images. The craft gathers data faster than anything that ever studied the sun.

To learn more about the SDO mission, visit: http://sdo.gsfc.nasa.gov

To find these videos for download, check out:http://www.nasa.gov/mission_pages/sdo/news/briefing-materials-20100421.htmland http://svs.gsfc.nasa.gov/Gallery/SDOFirstLight.html .


  • solar flare : Violent explosion on the sun’s surface.
  • solar prominence : Plasma loop flowing between sunspots.
  • solar wind : High energy particles that fly out from the sun.
  • sunspot : Cool, dark area on the sun’s surface that have lower temperatures than surrounding areas.


  • Sunspots occur in pairs. Each is one side of a loop of the sun’s magnetic field on the sun’s surface. Sunspots come and go on an 11-year cycle.
  • Sunspots are cooler and darker than the rest of the sun’s surface. They are marked by intense magnetic activity.
  • Solar prominences are the plasma loops that connect two sunspots.
  • Solar flares and coronal mass ejections are eruptions of highly energetic particles from the sun’s surface.


Use the resources below to answer the questions that follow.

  1. What are sunspots?
  2. What is a solar flare?
  3. How can solar flares affect Earth?
  4. Why do scientists study sunspots?
  5. What features do scientists study about sunspots?
  6. What is the normal sunspot cycle?


  1. What are sunspots? What is a sunspot cycle?
  2. How are solar prominences related to sunspots?
  3. What is being learned from the Solar Dynamics Observatory?

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