Unit Two: Investigating the Sun-Earth-Moon System
1. Sunspots Through Time
The sun is a constant in our lives. Day after day, year after year, it shines dependably and constantly. But, are changes in the output of the sun possible? Under the right conditions, ancient Chinese astronomers sometimes saw spots on the sun, but not always. Centuries later, Galileo also saw sunspots with his crude telescope and began to count them on a regular basis, an activity that modern solar observatories still continue. Every clear day, images are taken of the sun at observatories like the Big Bear Solar Observatory in California, or the National Solar Observatory on Kitt Peak in Arizona. These images provide a record you can use to investigate whether the sun is really unchanging or not.
Go to the Big Bear Solar Observatory Web site (BBSO): http://www.bbso.njit.edu/. Click on Images in the menu bar at left, and select Latest. The page that comes up gives you a selection of image available in the BBSO archive. These images show the sun in different wavelengths. Since the images are taken at the same time, they can be compared to each other. Access the archive of daily images by scrolling to the bottom of the page and clicking on FTP Archive. That will bring up a page with a folder for each year of solar observations at BBSO, beginning in 1982. Click on any year folder. You will see 12 folders for each month of that year. Click on a month folder to reach the daily image folders. Then click on a daily folder to get the archive images for that day. Look for files with "bbso_white_fi" in their names. These are the white light images. Click on these images to download them.
Navigate around the archive and collect one white light image for (about) each six months from the beginning of BBSO observations in late 1982. This will take a little persistence, since white light images were not taken every day due to bad weather or instrument problems.
- Open your images in a program like ImageJ and make a movie. Watch the movie and look for any changes in the number, size, and location of the sunspots. Do the sunspots change shape, size, or location (e.g., closer to the equator)? Are the changes regular or random over time? If the changes are regular, describe the pattern and frequency of change.
- Write up your observations and make a presentation to your class using your movie to what you have found.
- For an additional challenge, repeat the process, but this time using Hydrogen Alpha images (names "bbso_halph" in the BBSO archive), or ultraviolet images (http://sohowww.nascom.nasa.gov/data/soho_images_form.html) look for images with "171," "195," "284" or "304" in their names), or x-ray images (the Yohkoh site: http://umbra.nascom.nasa.gov/yohkoh_archive.html 1991 to 2001 only). How do changes in these images compare with the white light images?