The corona of the Sun is not usually visible to the naked eye; even though it is fairly bright, the Sun itself is so MUCH brighter that you cannot see it. Except during a solar eclipse, when the Moon blocks the direct rays of the Sun.
But astronomers can see the Sun's corona at any time,by using an instrument called a coronagraph; this device blocks the direct rays and allows astronomers to study the corona. Think of it as an artificial eclipse maker.
Sometimes, during a total solar eclipse, the corona of sun is visible to our eyes.
chromosphere
corona
CORONACORONA
There were partial solar eclipses visible from Phoenix including a 71% eclipse on April 7, 1940. There were no total solar eclipses visible in Phoenix during the 1940's.
The Umbra
The corona.
The outermost layer of the sun, corona, is visible during a total solar eclipse.
The red ring that is visible around the darkened disk of the Moon during a total solar eclipse is called the solar corona. It is the outermost layer of the Sun's atmosphere, composed of superheated plasma. The corona is usually invisible due to the overwhelming brightness of the Sun, but during a total solar eclipse, it becomes visible as a beautiful halo of red or white light.
The next solar eclipse will be a total solar eclipse on July 22, 2009. The eclipse will be visible in a path from northern India through China and across the Pacific ocean. It will not be visible in Europe or the Americas.
The last total solar eclipse for Dallas was Feb 20th 2008
The next total solar eclipse is on the 22nd of July, 2009. It will be visible in parts of Asia and the Pacific.