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Name ______Date ______
Partners ______
Astronomy Exercise #7: Sunspotsby ML West after Travis Rector
Objective: to become familiar with the sun and its sunspots
Equipment: PC with Scion Image, NOAO RBSE CD, calculator, Excel or graph paper, ruler
Background: The sun usually has several sunspots on its face. These are regions of somewhat cooler gas than the majority of the sun's visible layer. Because the sun spins on its own axis, the sunspots are carried across the sun's face and eventually disappear from our view on Earth. Sometimes they fade away, or new ones appear before the sun carries them around itself.
We will use astronomical digital images taken by the Kitt Peak Vacuum Telescope (KPVT) in Arizona, and are part of the Research Based Science Education (RBSE) CD-ROM written by Dr. Travis Rector of the University of Arizona. They are stored in FITS format (Flexible Image Transport System).
Procedure:
1. Turn on the PC and launch Scion Image (Start, All Programs, Scion Image, Scion Image) Click OK, OK to questions.
2.Insert the RBSE CD-ROM Pull down Special, Load Macros. Go to the CD, RBSE data, Software, Windows, Scion Image, Solar Macros (Select Solar Macros.txt)
3. Counting Sunspots
Open an image of the sun by pulling down Special, Import FITS. Look in the RBSE CD-ROM under KPVT Data and pick a date in 1999 Intensity or in 2000 Intensity. (Someone's birthday is a good choice.)
Date of your first image ______
Count the number of sunspot groups ______on the whole image.
Also count the total number of individual sunspots ______on the whole image.
On average, how many sunspots are in a group? ______(Divide the total number of sunspots by the number of groups)
Did you notice any group with a considerably higher number of spots in it? ______
The "sunspot index" for a day is (the number of groups) times ten, then plus (the number of individual spots).
Sunspot Index = (______x 10) + ______= ______
The official sunspot index is done counting really tiny spots, so your number will be smaller than the official number. Find the official sunspot number ______for your date at or the 2000 version.
The official SESC number is ______times your estimate.
4. Examining a single sunspot group
Pick the largest or most complex sunspot group on your image, and zoom in on it using the magnifying glass tool in the toolbox. Sketch the group:
Choose Special, Read Coordinates, then mouse click on the approximate center of the sunspot group. An Info window should give you the solar latitude and solar longitude of the group.
Solar Latitude ______Solar Longitude ______
We can also estimate the area of the sunspot group. Choose Options, Density Slice.
Use the LUT window to adjust the red density slice range. Make it so that the sunspots are highlighted in red, but not the surrounding brighter part of the sun.
Use the rectangle tool to select the whole sunspot group. Start in its upper left and drag to the group's lower right.
Choose Special, Sunspot Area.
Area in pixels ______
Adjusted area in pixels ______
Adjusted area (approximately) in km2 ______
5. Observing a sunspot group over time. Taking Data
Examine the image to find a sunspot group near the left-hand edge of the image. We want to make measurements of this group on successive days in order to track its motion and its area behavior.
Make the measurements and record them in the data table below.
Then load the image for the next date and make measurements of the same sunspot group for that day. Continue for seven days of good data. (Cloudy days do not count.)
RECALL: For loading use Special, Import FITS.
For latitude and longitude use Special, Read Coordinates.
For Area use Options, Density Slice. Do not change the red level. Use the rectangle tool to select the area, then Special, Sunspot Area to measure the red region inside the dotted rectangle.
Sunspot Group Data Table:
Date / Solar Latitude / Solar Longitude / Adjusted Area (km2)6. Analysis of the sunspot group over time
We want to make three similar graphs arranged vertically over each other.
Type your measurements into an Excel spreadsheet.
Label the horizontal axis of each graph "Date" and mark your seven dates near the center of the axis, leaving 7 days both before and after your week. (These days without data will soon come in handy.) An easy way to do this is to include the two extra dates (1 week previous and 1 week after your data) in your Excel spreadsheet, but without data for latitude, longitude, or area.
First graph:Label the vertical axis of your first graph "Solar Latitude" going from 0 to 90 degrees (or from 0 to -90), and plot your data. Draw a single straight trendline through the points as best you can. Describe the sunspot group's solar latitude vs. time:
Second graph:Label the vertical axis of your second graph "Solar Longitude" and make the scale go from -90 to +90 degrees, and plot your data. (Use Layout, Axes, Primary vertical axis, More options.) Draw a single straight line through the points as best you can. Fit a trendline and describe the sunspot group's solar longitude vs. time:
Extend this straight line until it exceeds -90 and +90 degrees. Mark these crossings. Count the days from -90 to +90 degrees in longitude. ______. This is how long the sunspot would take to cross the whole front of the sun. It would take twice as long to go all the way around the sun. This would be ______days.
How close did you come to the sun's accepted rotation period of 27.28 days? ______
Third graph:Label the vertical axis of your third graph "Adjusted Area" and choose a scale and plot your data. Sketch a curve through the points as best you can. Describe the sunspot group's area vs. time:
For your sunspot group is birth or death more gradual?
7. Future work in this field: