Science NetLinks: Sunspots 1: A Look at Sunspots

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	4A The Universe #3 Increasingly sophisticated technology is used to learn about the universe.... 4A The Universe #3 Increasingly sophisticated technology is used to learn about the universe....

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Sunspots 1: A Look at Sunspots

Purpose

Students will understand how the development of new technology has increased our knowledge of how the sun works.

Context

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 currently circling the sun (Yohkoh and SOHO 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 6-8 lesson entitled The Sun.

Planning Ahead

Materials:

Page 2 of the History section of Exploratorium's Sunspots online guide
Science NetLinks Student Sheet, Modern Research on Sunspots
Color transparencies of the following:**

A recent x-ray image of the sun (be sure to date it).
To obtain recent pictures of the sun, go to the Soft X-ray Telescope: Most Recent Images page of the Yohkoh Public Outreach Project website. Click on the Full Sun Image link to obtain a full-scale image of the sun.

Daily pictures of the sun are posted on this site. These pictures are 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. The spacecraft was built in Japan and the observing instruments have contributions from the U.S. and from the U.K. The name Yohkoh is Japanese for "sunbeam."
The electromagnetic spectrum.
A good Electromagnetic Spectrum diagram can be found at the Microworlds site from Berkeley Lab.
A visible light image, ultraviolet image, and x-ray image of the sun.
These images can be found at the Exploratorium's Sunspots online guide in the first page of the Modern Research section. Click on each image to obtain a larger, full-scale image of the sun. Do not label any of these images with the type of electromagnetic radiation used to visualize the sun.

**Note: This activity requires the use of color transparencies. However, if it is not possible to make color transparencies, black and white copies will suffice. An alternative to making color transparencies is to have students visit the sites at the school computer lab and make observations. Download times for the images should be checked before students view images at the computer lab.

Students will need to know how to use a Web browser. Students should also 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.

Both the Exploratorium and Yohkoh Public Outreach Project sites contain many images that may require significant time to view depending on the type of connection available. The approximate load times for images on these two sites are listed below for each corresponding connection type:

Connect Rate	Connect Time
14.4K	44.41 sec.
28.8K	24.60 sec.
56K	16.63 sec.
ISDN 128K	6.12 sec.
T1 1.44bps	1.81 sec.

Note: A short film is viewed as part of this activity. The film requires RealMedia plug-in player.

Motivation

Ask students:

What is the largest object in our solar system? (The sun-it contains 99.8% of the mass of our solar system.)

What is the sun made of? (Hydrogen and helium; 75% and 25%, respectively.)

How far away is the earth from the sun? (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 8264 miles away!)

Show students a recent, dated x-ray image of the sun taken by the Japanese Yohkoh satellite. The image should be on a color transparency.

Ask students:

Describe the features of the sun as seen in this image. (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.)

What are sunspots? (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.)

How do you think they are produced? (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.)

Why do you think scientists study sunspots? (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.)

How do you think scientists study sunspots? (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.)

What are some barriers to studying sunspots using technology? (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.

Development

Have students read page 2 of the "History" section of the Exploratorium's Sunspots online guide. Because this short reading is only one page, copies of the page can be made and distributed to each student for reading in the class. 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.

After all students have read the article, ask them:

Are sunspots visible to the naked eye? (Given the proper conditions such as fog, haze, or viewing the sun at sunset, it is possible to observe sunspots with the naked eye.)

What problems did astronomers face by viewing the sun with the naked eye? (Due to its intense brightness, looking at the sun directly is a very difficult and dangerous thing to do. Light from the sun can permanently damage the eyes. Students may be aware of the damage the can be caused by the sun during a lunar eclipse. In preparation for the eclipse, people are told to not look directly at the sun during an eclipse. That is because powerful ultraviolet radiation can severely burn and damage the eyes even though this form of light cannot be seen.)

How do you think the telescope changed the study of astronomy and specifically, sunspots, forever? (Telescopes not only protect the eye from direct contact with the sun, they also allow scientists to observe the sun and other solar bodies that are far away. With the invention of the telescope, observers were able to confirm the existence of sunspots on the sun and use the instrument to make detailed observations about their size, shape, and movement across the sun.)

Tell students that older telescopes, like our eyes, allow us to see in the visible light, or white light range.

Ask students:

What is visible light? (Students should know that visible light refers to the wavelengths of light that are visible to the human eye.)

If white light were exposed to a prism, what colors would emerge? (Red, orange, yellow, green, blue, indigo, and violet.)

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.

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.

Ask students the review questions at the Microworlds site using the picture of the electromagnetic spectrum:

What kind of electromagnetic radiation has the shortest wavelength? (Gamma rays)

What kind of electromagnetic radiation has the longest wavelength? (Radio waves)

What kind of electromagnetic radiation could be used to "see" molecules? (X rays)

What kind of electromagnetic radiation could be used to "see" a cold virus? (Ultraviolet)

Some insects, like bees, can see light of shorter wavelengths than humans can see. What kind of radiation do you think a bee sees? (Ultraviolet)

Distribute the student sheet, Modern Research on Sunspots, to each student. Have students read pages 1, 2, 4, and 5 of Modern Research, part of the Exploratorium's Sunspots 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 color transparencies of the visible light image, ultraviolet image, and x-ray image of the sun. These images can be found on the first page of the Exploratorium's Sunspots online guide Modern Research section. The color transparencies should not be labeled with the type of electromagnetic radiation used to visualize the sun.

Put up the images one at a time and ask students:

Which image depicts the sun through the use of visible light? (Allow students time to try to figure out which of the images shows visible light emitted by the sun. Then tell students which one of the three solar images is the visible light image. Label this image "Visible Light" with a transparency marker.)

Which image depicts the sun through the use of ultraviolet light? (Repeat above directions.)

Which image depicts the sun through the use of X rays? (Repeat above directions.)

Describe the features of the sun that can be seen using visible light that cannot be seen in the other two images using non-visible light. (Students should understand that the visible light picture of the sun shows what parts of the sun emit visible light. After comparing and contrasting the three images, students may state that the visible light image shows the surface of the sun and sunspots as dark and light regions on the surface.)

Describe the features of the sun that can be seen using non-visible light that cannot be seen in the image using visible light. (Students should understand that the non-visible light pictures of the sun show what parts of the sun emit non-visible light. For example, the UV image shows the parts of the sun that emit UV light; similarly, the x-ray image shows the parts of the sun that emit x-ray light. After comparing and contrasting the three images, students may state that the UV solar image seems to show a halo around the sun. The x-ray image shows active and calm regions on the sun.)

Where does ultraviolet fall in the electromagnetic spectrum? Does it have shorter or longer wavelengths than visible light? (This a review question. UV comes after violet in the visible light range and thus, has a shorter wavelength than visible light.)

Where do X rays fall in the electromagnetic spectrum? Do they have shorter or longer wavelengths than visible light? Than ultraviolet light? (X rays are at the end of the electromagnetic spectrum with the longest wavelengths. Thus, their wavelengths are longer than both visible and UV lights.)

If X rays show more detail than visible light, why do you think scientists still continue to take satellite pictures of the sun using visible light? (Each of the images shows different aspects of the sun. While X rays show details about the active vs. calm regions of the sun, visible light images detail the surface of the sun. These images used together give a more detailed picture of the sun that neither of these images could do alone.)

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? (Visible)

What is white light? (All wavelengths between 400 and 700 NM of the electromagnetic spectrum. These wavelengths correspond to red, orange, yellow, green, blue, and purple.)

Is red light visible or non-visible light? (Visible)

What is red light? (Light only in the red range at 400 NM)

How do you think a telescope takes a red light image of the sun? (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.)

Are X rays visible or non-visible light? (Non-visible)

How do you think a telescope takes an x-ray image of the sun? (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.

Ask students:

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? (The surface of the sun appears smooth and yellow with dark sunspots.)

How many sunspots can you count in this visible light image? (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 2000 km above the photosphere. The temperature of the chromosphere is anywhere between 6000 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? (It is bright and emanates out from the sun.)

How are the photosphere, chromosphere, and corona related? (These are all different parts of the sun that emit different types of light in the electromagnetic spectrum.)

How are active regions of the corona related to sunspots of the photosphere? (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.)

Assessment

Have students write their answers to the following questions in their own words. Have students 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?

Extensions
Follow this activity with the second and third lessons in the Science NetLinks series: Correlating Sunspots to Active Regions and Tracking the Movement of Sunspots.

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:

CNN: Sun aims powerful flares at Earth (3/1/00)
Seattle Times: Stormy weather forecast for sun could disrupt technology on Earth (2/23/00)

NASA: A Twisted Tale of Sunspots (2/29/00)
Australian Broadcasting Corporation: Sunspots and climate (4/12/99)

The following resources also post current findings about sunspots:

SpaceWeather.com has up-to-date information about the Sun-Earth environment

NASA: Sunspots and the Solar Cycle has up-to-date monitoring of sunspots and the solar cycle

Created :10/20/2001