Time Required: approximately 2-3 hours
We’ll start by looking at the solar interior more closely. Study the materials you’ll find at the Solar Interior
If you enlarge the image (by clicking on it), it shows you the various layers of the Sun. You can use this image along with your textbook to draw and label your diagram with both the inner and outer layers of the Sun.
Now use the website to read about what is occurring in each layer, and how we know this information.
In 1611 Galileo first looked at the Sun with his telescope and was surprised to view several dark blemishes on its surface which came to be known as “Sunspots.” Upon additional observations Galileo was able to determine that these sunspots were moving across the Sun’s surface indicating that the Sun, like the Earth, was rotating on its axis. The rate that sunspots move across the Sun’s surface can be used to determine the velocity of the Sun’s rotation.
On the Sunspot Tracking Images sheet are solar images for six consecutive days of several sunspot groups moving across the surface of the Sun taken by a NASA solar satellite known as SOHO, Solar and Heliospheric Observatory. You will be tracking three of these groups with this part of the activity. Sunspot group 1731 (near the equatorial area to the far left of the April 25th image), Sunspot group 1728 (above and to the right of Group 1731), & Sunspot Group 1730 (below and to the right of group 1731).
Important: In your typed lab report, clearly label all of your answers to the following questions. For any calculations below, be sure to show all of you work and not just the end answer. Make sure your worded answers are in full sentences. Any data in tables should be typed.
Identify and mark the same sunspot groups on each image (for the larger sunspot groups draw a circle around the whole group and mark a dot at the center of the circle as a reference point for your measurements). For reference, the North Pole of the Sun is the top of each image with the South Pole at the bottom. East is to the left of each image and West is to the right of each image.
For each sunspot group, use a ruler to draw a horizontal line from the left edge of the Sun’s image through the sunspot group and end the line at the right edge.
For each day measure the distance (in millimeters) from the Sun’s left edge to the center of each sunspot group. Create or copy the below table into your lab report. Record your data in the table.
Sun and Sunspot Groups
Date of Solar Image
Distance (in millimeters) from left edge of Sun
Group 1728
Group 1730
Group 1731
1
2
3
4
5
6
The distance that each sunspot group has traveled is the difference between the first distance entered in the table and the last distance entered in the table.
Sunspot Group 1730 ____________ mm
Sunspot Group 1731 ____________ mm
From one of the solar images measure the diameter, the greatest distance across the disk, of the Sun in millimeters.
The Scale factor for the images is simply the ratio of the diameter in kilometers (from step 3) divided by the diameter in millimeters (step 4).
Use this scale factor to calculate the actual distance the sunspot traveled. The actual distance = the distance the sunspots traveled in millimeters (step 2) × the scale factor (step 5).
Sunspot group 1730 traveled: ___________ km.
Sunspot group 1731 traveled: ___________ km.
Determine how fast the sunspots are moving across the surface of the Sun. The distance the spot traveled was calculated above. We know how long it took the spot to move this far, since we know the date of each photograph. The velocity is the distance the spots traveled divided by the time it took the spots to go that distance.
Each sunspot must travel a distance equal to the Sun’s circumference in order to make a full rotation around the Sun. As observed from Earth, the rotation period, or the time it takes a sunspot to go around the Sun once, is given by the Sun’s circumference divided by the rotation speed.
To know if your analysis makes sense, we should compare the measured value with the known value. The sunspots we have chosen for analysis are very close to the Sun’s equator.
[(measured value – known value) / known value] × 100% = ___________
You may have noticed in your calculations that the three groups of sunspots do not move across the surface of the Sun at the same velocity. Unlike the Earth, the Sun is not a solid ball on its surface but is a state of matter known as “plasma”. This allows to Sun to experience differential rotation of its surface.
The Sun is the energy source of all life here on Earth but it was unknown for a very long time what is the energy source of the Sun itself. Some suggestions included gravitational potential energy, energy created as the Sun gravitationally collapses in on itself, and chemical combustion, or “burning” as we would understand the term.
But both were quickly proven to be an inadequate energy source since, even with the humongous size of the Sun, they would not be able to maintain the energy output over billions of years needed for life to evolve here on Earth. Scientists had ample evidence to prove the age of the Earth at billions of years old and it would make no sense for the Earth to be older than the Sun.
The Sun creates its energy by nuclear fusion processes in its core through what is known as the Proton-Proton Chain. In this process lighter elements are fused into heavier elements releasing energy which powers the Sun (the amount of energy released is equal to Einstein’s famous equation E =mc2{“version”:”1.1″,”math”:”<math xmlns=”http://www.w3.org/1998/Math/MathML”><mi>m</mi><msup><mi>c</mi><mn>2</mn></msup></math>”}).
For this part of the activity you will be viewing a Proton-Proton Chain simulation created by the University of Nebraska-Lincoln. Follow this weblink for the animation.
Astronomy Education at the University of Nebraska-Lincoln. Astronomy Simulations and Animations. Proton-Proton simulation.
There are three basic steps involved in the proton-proton chain, first the formation of 2H, second the formation of 3He, and lastly the formation of 4He, Helium, the final product of hydrogen fusion. View the animation to answer the following questions (using complete sentences).
Higher mass stars however use a different method of energy production known as the CNO cycle. For this part of the activity you will be viewing a CNO Cycle simulation created by the University of Nebraska-Lincoln. Follow this weblink for the simulation.
Astronomy Education at the University of Nebraska-Lincoln. Astronomy Simulations and Animations. CNO Cycle Animation. (Make sure to answer in your own words an din complete sentences.)
NOTE: You must provide a reference list showing the source(s) that you used, including our own textbook, in proper APA citation format.
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