Viatouch
Teacher Articles
Science
Solar Eclipse: Seeing the Sun in the Shadow
by Amy S. Hansen
The mid-day sky darkens. A crowd of watchers grows quiet. After years of study, the disappearance of the Sun is still an occasion to stop and wonder.
For four minutes this March the Sun will be gone, hidden behind the Moon. The full eclipse will be seen in a small swatch of countries that includes parts of Brazil, Ghana, Egypt, Turkey, and Mongolia. But people from around the world will watch on television and on the Web.
What they're seeing is a matter of shadows. Put a lamp in a darkened room. Take off the lampshade. There is our Sun. Now take an orange (Earth) and a grape (Moon) and walk around the light. When the Moon comes between Earth and the Sun, the Moon's shadow will block out the Sun on parts of the Earth. It doesn't last long, and it isn't a very big shadow. But when it happens, people notice.
While watching the solar eclipse, people use special glasses to protect their eyes. The Sun seems to slip away. Suddenly, the middle of the day is dark. The temperature gets colder. Then bright lights appear around the edges of the Moon where the Sun is peeking out from behind. The lights are the corona (Greek for crown) of the Sun.
On Earth, a total solar eclipse makes it possible to catch a glimpse of the Sun's corona. The corona is a million times less bright than the center of the Sun. So on a normal day, it is hidden. But when the Moon's shadow blocks the bright Sun, suddenly we can all see pearly strands of energetic gas shooting off the Sun's surface.
In the 1800s, scientists who wanted to study the Sun had to move around the world, following the eclipses. They only got to see them for only a few minutes per year. From these studies, researchers learned for certain that the corona was attached to the Sun and not part of the Moon's shadow or something else.
Now scientists use satellites to see the corona 24 hours a day. From these satellites we know that the corona sends out the visible pearly strands and a lot of ultra-violet and x-ray energy—forms of energy that our eyes can't see. We also know that the gases on the corona are very, very hot. While the surface of the Sun is about 6,000 C°, the satellites show us that the corona is more like 1,000,000 C°. There are several theories, but scientists have yet to explain the difference in temperatures between the surface and the corona.
Sometimes that energy comes out. Great balls of energy shoot off of the Sun—like a campfire letting out a burst of flame. The burst of energetic, hot gas can reach Earth. We have a protective shield around the Earth that usually saves us from any harm, but we still feel the effects.
As the energy blows through space, it may damage our communication satellites, and astronauts need to take cover. When the solar burst's energy reaches Earth, we can sometimes SEE the results. The northern and southern lights are made much brighter by these corona explosions.
While beautiful, the Sun is not a quiet place. All of our lives are tied to the big ball of fire and we notice when it disappears. See for yourself. Watch the Sun hide behind the Moon on March 29 and remember your solar connections.
Watch the eclipse on:
http://www.exploratorium.edu/eclipse/
Follow news of the eclipse on these websites:
http://sunearth.gsfc.nasa.gov/evsecef.htm
http://sunearth.gsfc.nasa.gov/eclipse/SEmono/TSE2006/TSE2006.html
http://www.mreclipse.com/
Bibliography:
Espenak, Fred. 25 June 2005, personal e-mail.
"Our Sun Our Earth: Making Sun-Earth Connections." 2004. NASA SECEF/ OC Regents. CD-ROM. NASA: Greenbelt, MD.
"Space Weather. Seeing the Invisible." 2004. Space Update. CD- ROM. Rice University:
Houston, TX.
Thieman, Jim. "In a Different Light." Presentation at American Geophysical Union, 25 May 2005. New Orleans, LA.
Thieman, Jim. 25 June 2005, personal e-mail.
"Total Eclipse Solar Eclipses and the Mysteries of the Corona." 2003. Exploratorium and NASA's Sun-Earth Connection Education Forum. DVD. NASA: Greenbelt, MD.
Websites:
http://www.mreclipse.com/
http://www.spaceupdate.com
http://sunearth.gsfc.nasa.gov/eclipse/SEmono/TSE2006/TSE2006.html
http://sunearth.gsfc.nasa.gov/eclipse/TSE98reports/TSE98Espenak.html
Photos/Images:
http://sunearth.gsfc.nasa.gov/eclipse/TSE98reports/TSE98Espenak.html
http://www.mreclipse.com/
Photos courtesy of Fred Espenak - www.MrEclipse.com
