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Sunspots 3: Tracking the Movement of Sunspots

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Materials

 
Sunspots 3: Tracking the Movement of 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 circling the sun (SOHO and the now-defunct Yohkoh satellites).

Through the activities of lessons 1 and 2, students should now be familiar with sunspots, active regions, and the type of imaging used to visualize these features of the sun. In this activity, students collect one of two types of images gathered by the SOHO satellite currently circling the sun about one million miles from earth. Over a two-week period, students will obtain images directly from SOHO's official site on the Web and track the movement of sunspots using a latitude/longitude grid.


Planning Ahead

Sunspot Data Recording Worksheet, from the Stanford SOLAR Center site, will be needed for each student; one worksheet is used for each day of observations. If students have a science journal, students should make the tables by hand and fill them out with their observations. Remind students to title and date their tables if they make them in their science journals.

Transparencies of 2-3 intensitygram images and 2-3 magnetogram images will need to be made. Intensitygrams are color pictures; if possible, make a color transparency. Example images of an intensitygram and magnetogram can be found at the SOHO Daily Images site.

Latitude/Longitude Grids will need to be made on transparencies for students to measure the location of the sunspots. Two types of grids are available on the Stanford SOLAR Center site. The first grid represents the sun as how it would look in an image if the earth's orbit were exactly around the sun's equator. While this grid can be used, the Stanford SOLAR Center site also provides more precise grids for each month of the year. These monthly grids reflect the angle of inclination of the earth as it orbits around the sun. The grids may have to be sized to fit the dimensions of the solar images printed from the SOHO website. Sizing can be done with a copier machine. Enough transparencies of the chosen grid can be made for each student; or, a class set of transparencies can be made from which all students must share.


Motivation

Ask students these questions to review material learned from the previous activities in the sunspots lesson series. These questions are designed to get students thinking as they begin the two-week project:

  • How are sunspots studied?
  • Why is technology essential to the study of sunspots?
  • Do you think a sunspot can move across the surface of the sun?
  • How do you think scientists determine if and how sunspots move?

Development

Tell students that they will track the movement of sunspots across the sun using images collected daily by the SOHO satellite.

Distribute copies of the SOHO: Exploring the Sun student sheet. Students should use their SOHO: Exploring the Sun student esheet to go to the SOHO site and answer the questions using information from the site. This activity can be done as homework or during class in the school computer lab.

Review the SOHO: Exploring the Sun student worksheet to ensure that all students understand what SOHO is, its mission, and the purpose of the MDI (Michelson Doppler Imager) instrument.

Tell students that they will study images taken by the MDI instrument every day and measure sunspot locations over a two-week period. The MDI instrument takes two types of images: an intensitygram and a magnetogram.

Show students a transparency of an intensitygram and then a magnetogram. Tell them to ignore the white box that appears in the middle of the image.

Ask students:

  • Describe the difference between these two images.
    • (If the intensitygram image is on a color transparency, students will first notice that the intensitygram shows a bright sun while the magnetogram depicts a black and white image of the sun. Both images seem to show only the sun's surface or the photosphere.)
  • What features of the sun do you think the intensitygram shows?
    • (The intensitygram shows the surface of the sun.)
  • Are sunspots visible in the intensitygram? If so, how many can you count?
    • (Sunspots appear as dark areas since they are cooler areas of the sun. The number of sunspots will depend on the image shown.)
  • What features of the sun do you think the magnetogram shows?
    • (Students will likely say that the magnetogram also shows the sun's surface. Have them try to determine why a magnetogram has the word "magnet" in it. A magnetogram is actually images of the sun's magnetic field.)
  • Are sunspots visible in the magnetogram? If so, how many can you count?
    • (Sunspots in magnetograms appear as black and white areas. Each sunspot has a black portion and a white portion, or a south pole and a north pole respectively.)
  • Do the two images show a relationship between the sunspots they show?
    • (This will depend on the two images shown.)

Tell students that intensitygrams are pictures that show how bright, or how intense, the sun is. Because sunspots are cooler than the rest of the sun, they show up as dark spots on intensitygrams. In contrast, magnetograms are pictures of the sun's magnetic field. Sunspots are magnetic eruptions and therefore show up on magnetograms as dark and light areas. The rest of the sun that does not have magnetic eruptions shows up as gray in the magnetogram images.

Ask students:

  • Which type of image do you think is better for studying sunspot location?
    • (This will depend on whether students think that determining the area of sunspots is easier to do on intensitygrams or on magnetograms. Students may think that the black and white sunspots on magnetograms are too blotchy. On the other hand, intensitygrams often show a lot of cooler, dark areas that are not actually sunspots.)

Tell students to choose which image they want to study. Ensure that both images will be studied by approximately equal numbers of students in the class.

Distribute copies of the student sheet, Tracking the Movement of Sunspots to each student. Also give each student 14 copies of the Sunspot Data Recording Worksheet.

Go over the directions for the project with students. Tell students that over the course of a two-week period, they will obtain a minimum of ten images of the sun (either an intensitygram or magnetogram) from the SOHO's Daily Images site. They must consistently choose an intensitygram or magnetogram every day.

Images are taken by the MDI instrument every 96 minutes. Thus, there may be more than one intensitygram or magnetogram for each day. In that case, tell students to pick the image taken the earliest in the day (there will be a time given with each image).

Once students have obtained their images, they need to identify each visible sunspot cluster. Students should to measure only the large blotches and not worry about the smaller dots. They should name each cluster (number or letter) in order to keep track of it as it moves across the sun over time. They can write the name of the cluster directly onto the image.

Next, students must identify the latitude and longitude of each sunspot cluster. Show students a transparency of the latitude/longitude grid they will use. Place the grid over the transparency of the intensitygram. Show students how to measure the latitude and longitude of each sunspot cluster—read the latitude and longitude at the center of each cluster in the intensitygram. For the magnetogram, tell students to ignore the large white square in the middle. To measure the sunspots in the magnetogram image, students must measure to the center of the cluster between the black and white portions.

Put up other intensitygram and magnetogram transparency images and have students measure the latitude and longitude. This will allow them to become familiar and comfortable with the procedure. Show students how to record the data onto the Sunspot Data Recording Worksheet. You can see a sample of a completed worksheet on the Stanford Solar Center site. The worksheet shows how a student identified each sunspot cluster with a letter and noted the corresponding latitude and longitude for each. The worksheet also shows how one of the clusters (B) disappeared, demonstrating the volatility of the sun's atmosphere.

Students should fill in the end of the Tracking the Movement of Sunspots student sheet.

After thoroughly going over the directions, students should print out their first solar image for homework and bring the image to class. The activity requires students to download images of the sun on a daily basis and print them out for observation. If all students do not have access to computers at home, students may be divided into groups in which at least one member of the group can download and print images from the Web. If students cannot obtain daily pictures from the site, 15 sample images can be printed from the Teacher's page at the Stanford SOLAR Center's site.

In class, provide students with the longitude/latitude grid and have them fill out the data worksheet. This will ensure that all students are comfortable with the following:

  • Obtaining the correct images from the SOHO site on the Web.
  • Identifying and labeling sunspot clusters.
  • Measuring the location of each sunspot cluster using the latitude/longitude grid.
  • Recording information and observations into the table.

Assessment

Students should bring in all their pictures and data worksheets to class. Provide them with a blank sheet of paper and a latitude/longitude grid. Students should trace the shape of the sun onto the blank sheet of paper so that it is equal to the size in all their printed images.

Using the information from their data worksheets, students should use a pencil to mark the position of each cluster over the two-week time period. This will give students the opportunity to visualize the movement of each sunspot cluster over time. It may be easier for students to visualize the movement of each cluster if a colored pencil is used for each sunspot group.

Divide students into groups so that they can share their final diagram of the movement of sunspots with other students. Groups should include students who measured intensitygrams as well as students who measured magnetograms.

Ask students the following questions. Their answers will depend upon their individual findings over the two-week period. Through the discussion questions as well as their own efforts over the two-week period, students should express an appreciation of the technology used to study the sun, and in overall, the universe. They should also be able to compare and contrast their own findings with those of other students and discuss constraints and other issues involved in gathering data. Students should also, as a class, reach a consensus about the movement of sunspots across the sun.

  • In general, how would you describe the movement of sunspots over time?
  • Describe the types of trends you noticed about sunspots over time.
  • How do the intensitygram findings differ from the magnetogram findings?
  • How do you explain the differences between the intensitygram and magnetogram findings
  • Were there differences between the findings of one intensitygram to another?
  • Were there differences between the findings of one magnetogram to another?
  • How would you explain the differences between images of the same type?
  • How was technology an essential part of this study?
(Answers may vary. Encourage students to explain their answers.)

Extensions

Students can project an image of the sun on a sheet of white cardboard, using binoculars or a small telescope. The activity allows students to observe sunspots, and watch the sun rotate from day to day. This activity can be a long-term project in which students monitor the movement of sunspots. The activity is described in the Exploratorium's Sunspots online guide.


Students can study other aspects of the sun using SOHO data collected daily. The SOHO site has six lessons designed for high-school students that study the following aspects of the sun using real-time data. These lessons can be found on the SOHO Lesson Plans page.


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