Name
Class
Phys1411
Sunspots and Solar Rotation
Part 1: Read and understand the Introduction
Read and understand the introduction that is provided to you with this worksheet. Find a partner to discuss these
concepts and ideas. You can work together with a partner but you must do your own individual work and submit
individual worksheet.
Part 2: Sunspot Data Table
Using the SOHO images provided in the introduction document record the data for each group of sunspots. Do not
choose more than one sunspot from the same sunspot group. Estimate the number to the nearest whole degree. Also
record the average latitude.
Group A
Group B
Group C
Avg. Latitude:
Avg. Latitude:
Avg. Latitude:
Date
Time
Longitude
1
Longitude
Longitude
Part 3: Data Analysis
The goal here is to find the rotation period of the sun, to do that we need to process the data so we can perform the
necessary calculations.
1. Calculate how far each sunspot group has moved from one day to the next by subtracting the smaller longitude from
the larger. Record the result to the nearest whole degree in Table 2.
2. Recall that the Earth moves around the Sun in the same direction as the sunspots, so we are chasing the sunspot by
about 1 degree per day. To compensate for this Earth motion, we need to add 1 degree per day to our longitude
difference. Record the corrected longitude change in Table 2.
3. Assuming that the sunspots do not physically change their position on the sun over the course of a day we can
calculate the period of rotation (in days) using the following proportion.
360 𝑑𝑑𝑑𝑑𝑑𝑑𝑑𝑑𝑑𝑑𝑑𝑑𝑑𝑑
𝑐𝑐𝑐𝑐𝑐𝑐𝑐𝑐𝑐𝑐𝑐𝑐𝑐𝑐𝑐𝑐𝑐𝑐𝑐𝑐 𝑙𝑙𝑙𝑙𝑙𝑙𝑙𝑙𝑙𝑙𝑙𝑙𝑙𝑙𝑙𝑙𝑙𝑙
=
𝑋𝑋 𝑑𝑑𝑑𝑑𝑑𝑑𝑑𝑑
1 𝑑𝑑𝑑𝑑𝑑𝑑
Solve for X and do the calculation for each corrected longitude in Table 2.
4. Calculate the average rotation period to the nearest tenth of a day and record it in Table 2.
5. Repeat steps 1-4 for the rest of the sunspot groups.
Table 2 Sunspot Group A
Day 2 – Day 1
Change in Longitude Form Table 1
Corrected Longitude Change
Day 3 – Day 2
Day 4 – Day 3
Day 5 – Day 4
Day 6 – Day 5
Day 7 – Day 6
Day 8 – Day 7
Day 9 – Day 8
Day 10 – Day 9
Day 11 – Day 10
Day 12 – Day 11
Average Rotation Period:
2
Period of Rotation
Table 2 Sunspot Group B
Day 2 – Day 1
Change in Longitude Form Table 1
Corrected Longitude Change
Period of Rotation
Day 3 – Day 2
Day 4 – Day 3
Day 5 – Day 4
Day 6 – Day 5
Day 7 – Day 6
Day 8 – Day 7
Day 9 – Day 8
Day 10 – Day 9
Day 11 – Day 10
Day 12 – Day 11
Average Rotation Period:
Table 2 Sunspot Group C
Day 2 – Day 1
Change in Longitude Form Table 1
Corrected Longitude Change
Day 3 – Day 2
Day 4 – Day 3
Day 5 – Day 4
Day 6 – Day 5
Day 7 – Day 6
Day 8 – Day 7
Day 9 – Day 8
Day 10 – Day 9
Day 11 – Day 10
3
Period of Rotation
Day 12 – Day 11
Average Rotation Period:
6. Results: summarize your rotation period in the table below in order of increasing latitude from the equator.
Sunspot Group
Average Latitude
Rotation Period
a. Do your results show differential solar rotation: __________________________________
b. How can you justify your answer to a) with evidence or data?
Questions:
1. What would you need to do to improve the accuracy of your results?
2. How is the rotation of Earth different from what you find for the Sun?
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3. What other planets in our solar system might show differential rotation?
4. Inspect the images carefully. Do the sunspots form as a single entity, in close pairs or in groups. Explain.
5. From the images, it is possible to calculate how many Earths will fit in one of the large Sunspot. Assume that the Sun
is 100x the diameter of Earth. Identify the largest sunspot from group A, B or C in the images and calculate what is
its diameter in terms of Earth diameters. Print and attach the image you are going to use for this calculation and
explain and show how you did your calculations.
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