These pages let you explore the sun at different times in the solar
cycle, and using different frequencies of light (white, x-ray, h-alpha,
and extreme ultraviolet). Read below for more information, or go
straight to the interactives: SolarMax,
Seeing the Sun in Different Ways
|| A schematic view of the sun showing
the different layers of the solar atmosphere and the light
we can use to see it.
When you look at something, your eye interpretes different frequencies
of light as different colors. But there are far more frequencies
of light than your eye can see. Infrared, ultraviolet, x-rays and
microwaves may not be visible to your eye, but we can see them with
specially designed instruments, and use them to learn more about
On the sun, different frequencies of light are formed in different
parts of the solar atmosphere. That means that if we filter the
light so that we see only a particular frequency, we can see different
layers of the sun's atmosphere. The visible layer of the sun's atmosphere
-- the part that produces visible light -- is called the photosphere.
Above that is the chromosphere, which produces ultraviolet light,
and above that is the solar corona, which produces x-rays. At 1
million degrees F the corona is the hottest part of the solar atmosphere.
explore the different layers of the sun, click on the icon at right.
For more information on the the different frequencies of light
used by these filters, and how they are formed, click here.
The Solar Cycle
Like Earth, the Sun has seasons. More precisely, it has a cycle
that lasts about 11 years. During the peaks of this cycle, the sun
is much more active, with many sunspots visible on its surface.
Click on the dates to explore the sun near solar minimum, near solar
maximum, or mid-way between minimum and maximum.
|The current solar cycle, showing actual
results (yellow) and predictions for the future (white and
blue). For the latest information vist the Space
What You Need to View These Pages
These pages require a browser compatible with Java 1.2 or better.
Reasonably current versions of Internet Explorer on the PC or Macintosh
should be able to view them. Netscape may require the most recent
version, especially on the Macintosh.
These pages will need to load several images, so it may take some
time to download over a modem. The applet will begin working before
all the images are downloaded, so don't let that confuse you!
Some questions to ponder
- How do sunspots (the dark areas in the white-light image) look
using the different filters?
- Do regions that look active in one filter always look active
in another filter?
- Can you make any guesses about whether magnetic fields are important
factors in solar activity?
- Look at the sunspots using the magnetogram filter. Can you guess
why sunspots tend to appear in pairs or groups?
- You might notice that the different solar images are not perfectly
lined up. The images start out at different sizes and orientations,
and are scaled and rotated to line up as well as possible. In
addition, though, the images were taken at somewhat different
times, with up to a maximum of a few hour gap. The sun rotates
once on its axis in about 27 days. How big a difference do you
think this few hour difference makes?