There are many telescopes up in space constantly observing the Sun. The Sun is the closest star to Earth, and is the easiest to study. By studying the Sun in detail, astronomers learn more about stars in general.
In this activity, we will explore the Sun by looking at almost live images of the Sun, taken in different wavelengths.
Go to : http://helioviewer.org/
The center of the page is the viewing screen, where you see the most current view of the Sun, and where you can zoom in and out. On the left, you will see the “Images” box where you can select different satellites and wavelengths to view the Sun.
I. Tracking Sunspots
1. Start with the latest images from the Solar Dynamics Observatory (SDO). In the “Images” box on the left, set the “Observatory” to SDO, the “Instrument” to HMI, and “Measurements” to “continuum”. With these settings, the Sun should look very similar to what you'd see through a telescope with a solar filter.
2. The Sun is pretty smooth and featureless today. It was a little more interesting a year ago, so let’s travel back in time. In the upper left corner, set your observation date to 2017/07/12.
3. Can you see any features on the Sun? Is it smooth? Spotty? Sketch what you see on the worksheet.
4. In the top right corner of the viewing screen is a box that shows the scale of the Earth. You can click and drag the box around the viewing screen to compare the size of the Earth to the features on the Sun.
If any sunspots are visible, how do they compare to the size of the Earth?
The Helioviewer has a huge collection of images of the Sun taken since 1950. With all this data, we can see how the Sun changes and moves. Just like the Earth and every other planet in the Solar System, the Sun too rotates on its axis. The Earth rotates once every 24 hours. How long does it take the Sun to rotate on its axis? How long is one “day” on the Sun?
By watching the sunspots move over time, astronomers know that the Sun takes about 25 days to rotate once. Using the data in Helioviewer, we can make a movie of the Sun and watch the motion of sunspots!
5. Click on “Create a Helioviewer Movie” at the top right corner of the viewer screen. In the “Generate a Movie” box (shown above), choose “Full Viewport”. In the “Movie Settings” box, set “Duration” to 28 days and click “OK”.
6. This step will take a few minutes, a lot of images are being collected and put together! While your movie is being generated, you can continue to use Helioviewer to view the Sun. Explore images taken in other observatories, instruments, and wavelengths. Find more cool features!
7. Once your movie is done, click the “Generate a Movie” button again, and find your movie as “HMI continuum” under “Movie History”. Click on it to load your movie.
8. Play your movie! Watch how the sunspots move.
Do any of the sunspots make it all the way around the Sun in your 28 day movie?
9. You can save your movie and view it at home! Click on “Download Movie” in the bottom left corner and save it anywhere you want as <your-movie-name>.mp4.
2. Comets and Coronal Explosions
Space telescopes looking at the Sun capture a lot of cool events! Below are a couple of these that happened a few years ago. Explore them!
1. We're going to load two layers of images. Set the Observatory to “SDO” as before. Change the Instrument to “AIA” and the measurement to “304”. This is image of the Sun in ultraviolet light!
2. Next, we're going to add another layer. Click on “+ Add Layer” next to Images. Another box will open below your first one. In this new box, set the “Observatory” to “SOHO”, the Solar and Heliospheric Observatory Telescope. Choose the Instrument “LASCO”, detector “C2”, and the measurement “white-light”. This instrument shows the hot, dim, outer layer of the Sun, called the “corona”, by blocking out most of the Sun. Your settings should look like this:
3. Zoom out a couple of times to see the entire image, which should look like this:
Comet ISON gets destroyed by the Sun!
1. The comet passed 725,000 miles from the Sun, which was simply too hot.
2. In the “Observation Date” box, just above the Images box, set the Date to “2013/11/28”, or November 28, 2013, and the “Jump” to “1 Hour”, like this:
3. Now generate another movie in Full Viewport, with the “Duration” set to 2 days.
A large explosion on the Sun, known as a “coronal mass ejection”
1. In the Observation Date” box, set the Date to “2013/08/20”
2. In the “Features and Events” window, select the “CME” box. This will label where the coronal mass ejections are.
3. Generate another movie in Full Viewport, with the “Duration” set to 2 days.
4. Do the same for 2012/01/22. Try adding another layer, this time LASCO C3. (And zoom out!)
5. Watch and enjoy all three movies when they're done!
If you're finished early, play around with the Helioviewer by adding multiple image layers from different satellites. Find other cool events, make more movies.