Sunspots: Calculating the Rotation Period of the Sun

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Author: Jennifer, Grade 7


This project concerns activity happening millions of miles away, on the sun. Sunspots are cooler, dark regions of the sun where the magnetic fields are disturbed. They are signs to an active sun. They can disrupt commutations on Earth when there is a solar maximum, or many sunspots and activity on the sun. A solar maximum is apart of the 11 year sunspot cycle. At the beginning of the cycle there are few sunspots, solar minimum, then gradually more appear, solar maximum, then it returns back to a solar minimum.

I have an interest in the sun, so I chose to perform this project. The problem is to discover the rotation rate of the sun and if there is a daily change in the number of sunspots. The other problems were to find the duration of sunspots, and if there are changes in the sizes of spots. It was hypothesized that there would be a smaller amount of large sunspots when compared to lesser ones and that they will last up until 30 days. It was also predicted that the rotation period of the sun determined by sunspots would be about 27 days. I believe that all sunspots will gradually increase in number and appear more frequently near the equator of the sun.

To answer the problems, accurate maps of the sun were received by logging on the Internet and visiting NASA's web site. The angle in which a sunspot had moved over a period of time was found next. To find the total number of sunspots, the sunspots were grouped into sizes by comparing a mark on an index card to the spot on the maps. The groups were >3mm, 2-3mm, 1mm, and <1mm. The sunspots in each group were totaled to find the variation in the number of spots. I also mapped the sun on my own using a reflecting telescope and a piece of white paper.

It was found that it takes the sun about 26 days to make a complete rotation, which is close to the actual rotation period, and my prediction of 27 days. It was also found that there are more less than 1mm marks than any other size. Next came 1mm, 2-3mm and, the least most occurring size of a sunspot is greater than 3mm. The number of sunspots varied from 18 spots to 52 spots. The predictions that were made were correct! Scientists can use my data to more thoroughly understand the sun and sunspots. I now look at the sun in a different 'light'.

Background Information

What is a Sunspot?

A sunspot is a cooler, dark region of the sun that is magnetically disturbed. Magnetic fields produce pressure, and this pressure can cause gas inside a sunspot to become equal with the gas outside of a spot, but now at a lower temperature. The darkest part is the umbra, (the center portion) and is about 4500 Kelvin. Surrounding the umbra is the penumbra, a hotter portion of a sunspot. The penumbra is typically 5500 Kelvin, and appears lighter than the umbra because of the change in temperature. An average sized sunspot is as large as the Earth.

Solar Radiation

The sun produces many different types of light in the core. Scientists with new tools have captured the sun's emission and therefore scientists are able to compare the results and it gives them a new way to examine the sun. The energy produced by converting hydrogen into helium is carried outward into the convection zone, which is the outer 20-30% of the sun. The sun is so massive that it takes about 50,000,000 years for energy produced in the core to make it to the surface. Magnetism is the key to understanding the Sun. Magnetism, or the magnetic field, is produced on the Sun by the flow of electrically charged electrons. Magnetic fields are the root of all activity on the sun.

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