To help students understand how the development of new technology has increased our knowledge of how the sun works.
Ultimately, the sun is the source of all life on earth, providing light and warmth to the organisms that inhabit our planet. As a result, the sun has fascinated humans throughout history: it has been worshipped as a god, observed as it moves across our skies, and studied for its composition and behavior. Many cultures have built observatories to monitor the sun and its observable properties. As technology becomes increasingly sophisticated, we have been able to gather more and more information about the sun and use this data to infer things about the star's behavior.
This activity is part of a three-part series of lessons aimed at showing students how our knowledge of the universe must be inferred through the use of scientific tools. Specifically, students study sunspots in these lessons through the use of solar imaging from satellite instruments circling the sun (SOHO and the now-defunct Yohkoh satellites).
In this lesson, students are introduced to sunspots and the types of technology and solar imaging that can be used to collect information about the sun's features. The second and third lessons in the series are activities in which students apply information gathered by scientific instruments (telescopes and satellites) to infer knowledge about the behavior of sunspots.
In middle school, students should have had some introduction to the sun such as that provided in the Science NetLinks lesson entitled The Sun.
Students should be familiar with the electromagnetic spectrum and the properties of light (wavelength and frequency). Although this activity includes a brief review of light, this activity should not serve as an introduction to visible and non-visible energy.
Daily pictures of the sun were posted on the Yohkoh Public Outreach Project site. These pictures were taken by the Japanese Yohkoh satellite, an observatory for studying X rays and gamma rays from the sun. The satellite was launched from Kagoshima, Japan, on August 31, 1991, and operated until December 14, 2001. The spacecraft was built in Japan and the observing instruments had contributions from the U.S. and from the U.K. The name Yohkoh is Japanese for "sunbeam."
To begin this lesson, engage your students in a discussion by asking these questions:
- What is the largest object in our solar system?
- What is the sun made of?
- How far away is the earth from the sun?
- (The sun. It contains 99.8% of the mass of our solar system.)
- (It is made of hydrogen and helium; 75% and 25%, respectively.)
- (Often students, as well as adults, do not appreciate the vast size and layout of our solar system. To give students a visual of the distance between the sun and the earth, show students a beach ball to represent the sun. In this case, the earth would be the size of a pea, situated 164 feet, or 50 meters, away. A good way to show this to students is to measure the length of the classroom in feet using a tape measure and then extrapolate how much further earth should be from the sun if the beach ball is held at one end of the room. It will also surprise students to know that in this case, the next nearest star would be located on the other side of earth (away from the sun), 13,300 km or 8,264 miles away!)
Show students a dated X-ray image of the sun taken on the Yohkoh Public Outreach Project site. You can project the image on a screen or make use of a SmartBoard.
- Describe the features of the sun as seen in this image.
- What are sunspots?
- How do you think they are produced?
- Why do you think scientists study sunspots?
- How do you think scientists study sunspots?
- What are some barriers to studying sunspots using technology?
- (Students may mention the corona, as well as the bright and dark regions of the sun. They may also mention sunspots. Using a transparency marker, parts of the sun's X-ray image can be labeled.)
- (Students should brainstorm about what they think a sunspot is. Students will likely say that sunspots are flares rising up from the sun. Students do not need to know the technical definition of a sunspot. As they continue with the activity and read, their idea about what a sunspot actually is will be clarified.)
- (Students may have various theories and ideas about how sunspots are formed. These ideas can be brainstormed and listed on the board or a chart pack. As students do the activity, their ideas about how sunspots are formed will be clarified.)
- (Students should consider why studying sunspots and the sun in general are important fields of research. Our planet, as well as the entire solar system, receives its light from the closest star, the sun. Without the sun, there would be no life on earth. It is important to study and understand something as important as the sun because what happens on the sun and to the sun, ultimately affects our life on earth. Moreover, many scientists contend that sunspots directly affect our weather patterns on earth. By understanding sunspots, how they are formed, and their cycles on the sun, we are better equipped to deal with changes in our environment on earth.)
- (Through telescopes, satellites, and a multitude of imaging instruments that take different types of pictures of the sun. Students may not propose imaging instruments. This activity will add to their knowledge about the types of tools used by scientists to study the sun.)
- (Distance of the sun and the heat does not allow humans or instruments to get too close to the sun.)
Tell students that the solar picture is an X-ray image. The image was made by focusing the X rays that are produced by the sun's hot outer atmosphere. X rays are produced where the temperature of the super hot gas (or "plasma") reaches more than a million degrees, and where the density of the plasma exceeds a certain threshold. This occurs at the sun's outermost atmosphere, the corona. Since X rays are invisible, the image has had false-color applied so that one can see where the hottest, most dense, plasma is located.
Tell students that it was only 50 years ago that we learned that the sun produces X rays. Thus, the study of the sun through X-ray imaging is a relatively new science.
Students should use their student esheet to go to and read page 2 of Sunspots: History. Students can read out loud or silently for an allotted period of time.
Note: Mention is made of a scientist named Dearborn in the short reading. David Dearborn is an astronomer and stellar physicist. In particular, he is an archeoastronomer, studying the knowledge, myths, and ideas held by ancient civilizations about objects in the universe, such as the sun.
As students go through the resource, they should answer the questions on their student sheet. You can find answers on the A Look at Sunspots teacher sheet.
Remind students that light is a wave and different types of radiation travel at different wavelengths. For example, visible light travels at wavelengths between 400 and 700 nanometers. Only objects within that size range will absorb and reflect light of that wavelength. For example, we cannot use visible light to visualize atoms because atoms are much smaller than 400–700 nm. Similarly, microwaves do not pass through the holes of the microwave door because the holes are smaller than 1200 mm (the size of microwaves). The shorter the wavelength, the more detailed information you can get about an object.
Show students a color transparency of the electromagnetic spectrum. A good image can be found at Microworlds: Exploring the Structure of Materials from Berkeley Lab.
Ask students the review questions at the Microworlds site using the picture of the electromagnetic spectrum. Again, you can find answers on the teacher sheet.
Distribute the Modern Research on Sunspots student sheet to each student. Students should read pages 1, 2, 4, and 5 of Sunspot: Modern Research online guide, and answer the questions on the activity sheet. After students have finished the reading and activity sheet, review students' answers to the questions.
Show students the visible light image, ultraviolet image, and X-ray image of the sun from the first page of the Sunspots: Modern Research section. You can project them on a screen or use a SmartBoard.
Put up the images one at a time and ask students the questions on the teacher sheet:
Tell students that they will view a very short film that depicts the sun through white light, then red light, and finally through X rays. The film, which is called Wavelength Fade, is located at the Yohkoh Public Outreach Project.
Before showing the film, ask students:
- Is white light visible or non-visible light?
- What is white light?
- Is red light visible or non-visible light?
- What is red light?
- How do you think a telescope takes a red light image of the sun?
- Are X rays visible or non-visible light?
- How do you think a telescope takes an X-ray image of the sun?
- (It is visible light.)
- (All wavelengths between 400 and 700 nm of the electromagnetic spectrum. These wavelengths correspond to red, orange, yellow, green, blue, and purple.)
- (It is visible light.)
- (It is light only in the red range at 400 nm.)
- (The telescope is equipped with a filter that only detects red light that is emitted. In effect, it filters out all other wavelengths emitted by the sun and reads only wavelengths in the 400 nm range, or the red range. The resulting image shows parts of the sun that emit red light only.)
- (They are non-visible light.)
- (The telescope filters out all other wavelengths except for those that correspond to X rays. The resulting image shows parts of the sun that emit X rays.)
Show students the movie. This movie is very quick because it is only a few frames. Thus, the movie may need to be played multiple times. It may be helpful to pause the movie while it plays to better visualize frames at a time.
- How do the features of the sun change as the film goes from visible light to red light and finally to X rays?
- (Students should discuss how the sun looks different through the short movie.)
Tell students that the white light image shows the photosphere of the sun. The photosphere is the surface of the sun. This is what we see when we look at the sun using our eyes. (Directly looking at the sun can cause blindness.)
Pause the film at an image of the sun in visible light. Ask students:
- What does the photosphere of the sun look like?
- How many sunspots can you count in this visible light image?
- (The surface of the sun appears smooth and yellow with dark sunspots.)
- (There are four sunspots that can be seen in the visible light image.)
Tell students that the red light image shows the chromosphere of the sun. The chromosphere is a thick layer of gas located 2,000 km above the photosphere. The temperature of the chromosphere is anywhere between 6,000 to 50,000 degrees Celsius.
This layer of the sun gives off red light, which is why it can only be visualized using a telescope that filters out all other light except red light.
Pause the film at an image of the sun in red light. Ask students:
- What does the chromosphere of the sun look like?
- (It is red with some dark lines or filaments running through. These dark filaments are cooler parts of the sun, which don't give off as much red light. For this reason, they appear as dark areas of the chromosphere.)
Tell students that the X-ray images show the sun's corona, the outermost layer of the sun's atmosphere. The corona is very thin and faint and cannot be observed from earth. The corona emits energy of various wavelengths, including radio waves and X rays. However, all parts of the corona do not emit the same amount of energy. The most active regions emit the most X rays and are usually right above the sunspots that scientists see through visible light images. X-ray images of the corona show that this part of the sun is very stormy and constantly changes.
Pause the film at an image of the sun in X-ray energy. Ask students:
- What does the corona of the sun look like?
- How are the photosphere, chromosphere, and corona related?
- How are active regions of the corona related to sunspots of the photosphere?
- (It is bright and emanates out from the sun.)
- (These are all different parts of the sun that emit different types of light in the electromagnetic spectrum.)
- (Students may state that sunspots seen on the sun's surface are the active regions of the sun's corona. They may also suggest that the sunspots cause active regions to exist in the corona.)
Students should write their answers to the following questions in their own words. They can refer to the Exploratorium Sunspots online guide to help them. These questions review of the content introduced in this activity and assess that students can identify the types of technology used to study the sun and how these tools are used.
- Describe the types of solar imaging used to visualize the sun and its features.
- How do the different types of solar imaging differ from one another in terms of what they tell us about the sun?
- How does the use of technology aid in our understanding of the sun?
- Why is the study of the sun and its features important to our life on earth?
Students can research the technology used to observe the sun over time in different civilizations. Such a research project will give students the opportunity to appreciate the contribution of many cultures to our general understanding of the universe today.
- The Exploratorium Sunspots online guide has information about various cultures, including a RealMedia audio clip in which David Dearborn discusses the importance of the sun in ancient cultures.
- More information about Galileo's work with sunspots can be found at the Galileo Project website on these pages:
- Ancient Astronomy lists various observatories constructed by people over time to observe the universe. Students can use this list to identify a civilization and research the types of technology employed to study the sun.
Students can research current findings about sunspots and how their activity affects life on earth. This can be done on an individual student level. The activity can also be done in groups; each group can be assigned an article and make a formal presentation to the rest of the class. Some recent articles about sunspots include:
- The New York Times Green Blog: A Better Yardstick for Measuring Solar Cycles (1/19/11)
- Stormwatch 7 Blog: Solar Flares and Sunspots: Yes, There's an App for That (2/10/11)
- National Geographic Breaking Orbit Blog: Here Comes the [Entire] Sun (2/7/11)
The following resources also post current findings about sunspots:
- SpaceWeather.com has up-to-date information about the Sun-Earth environment
- NASA: The Sunspot Cycle has up-to-date monitoring of sunspots and the solar cycle