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Sunspots: Calculating the Rotation Period of the Sun (page 2)

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Author: Jennifer, Grade 7

The Sunspot Cycle

Sunspots follow an approximate cycle between 9.5 and 11 year, on average 10.5. Heinrich Schwabe was the first to note this cycle in 1843. The part of the cycle with high sunspot action is called a solar maximum. When there is little action it is called a solar minimum. Scientists have found that at the end of each cycle the magnetic poles of the sun switch. After the next 11 years the poles return to their original positions. The sunspot cycle results from the recycling of magnetic fields by the flow of energy in the interior.

History

In 1611 Italian astronomer Galileo, discovered dark blotches on the sun. Chinese astronomer also reported sunspots as early as 200 BC, but they did not think of the sun as an evolving body. Galileo's discovery marked the beginning of a new approach to the studying of the sun. The sun was then viewed as an evolving body, and its properties then could be understood scientifically.

Effects on Earth

Sunspots, as well as solar flares, have effects on Earth. From 1645 to 1715 there was a mini ice age in Europe. During this time almost no sunspots were detected. Some tree rings show that their growth is affected in the 11 year cycle of sunspots, but this is now under investigation by scientists. Sunspots tell us that are sun is active. An active sun can cause geomagnetic storms that disrupt commutations, endanger satellites, and disrupt power systems on Earth. An active sun can give airplane passengers a dose of radiation equivalent to a medical x-ray. It also heats the Earth's atmosphere so that spacecrafts are exposed to more atmosphere drag.

Size and Number

Sunspots change in size and shape, and usually last about 30 days, but some can last much longer or shorter. In the beginning, a group of sunspots develop and become visible. Then, the sunspots spread apart and grow in the next 5 to 10 days. Next, the group begins to disappear over the next couple of weeks.

Duration and Rotation Period

Scientists have found that the sun takes 27 days to complete one rotation. The average sunspot lasts for several days, but some have lasted for weeks. Since the Sun is a ball of gas it and not solid it does not rotate like the solid planets and moons do. In fact, the Sun's equatorial regions rotate faster, taking about 24 days, than the polar regions, which rotate once in more than 30 days. The source of this different rotation is under current research in solar astronomy.

Problem and Hypothesis

Problem

  1. What is the rotation rate of the sun determined by sunspots? (See Table)
  2. Is there a daily change in the number of sunspots?
  3. What is the duration of sunspots?

Hypothesis

  1. I predict that the rotation period of the sun will be about 27 days.
  2. I hypothesize that all sunspots will gradually increase in number and appear more frequently near the equator of the sun.
  3. I predict that there is a smaller amount of large sunspots when compared to small ones and that they will last up until 30 days.

Procedures: Mapping

Method #1: Use reflecting telescope

  1. Take telescope outside and put on a stool.
  2. Line sun up with center of telescope.
  3. Take a piece of white paper and draw a circle on it. Place on clipboard.
  4. Focus image and line it up inside circle.
  5. Have a friend hold the clipboard and with a pencil make a mark where you see a sunspot. Remember, the image is backward.

Method #2: Download from Stanford University

http://sohowww.nascom.nasa.gov/data/synoptic/sunspots/

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