Learning about solar eclipse, Lunar eclipse and corona of sun

 What is a solar eclipse?

You probably know that the earth travels around the sun and the moon travels around the earth. As the moon revolves around the Earth, it passes between the Earth and the sun once every month. But the orbit of the moon around the earth is not in direct line with the earth’s orbit around the sun. So the moon usually does not pass directly in front of the sun. But when it does, it blocks out part or all of the sun and this event is called a solar eclipse.

The sun is much bigger than the moon but is so far away that the moon can cover it up, just as you cover up a distant house when you hold your hand before your face. When the moon is between the sun and the earth, the moon throws a shadow on the earth. This part of the earth covered by the shadow is in darkness. Thus a solar eclipse can’t be seen from all parts of the world. An eclipse never lasts more than about seven and a half minutes. The greatest number of solar eclipses possible in a year is five.

What is a lunar eclipse?

When the moon passes directly between the sun and the earth, we have a solar eclipse. When the earth passes directly between the moon and the sun, a lunar eclipse occurs. A lunar eclipse can occur only on full moon nights because only then it is on the other side of the earth from the sun. The earth casts a long shadow on the moon and we can see the lunar eclipse.

There may be no lunar eclipse in a year or there may be as many as three. A lunar eclipse can last much longer than a solar eclipse, up to 104 minutes.

Which is the brightest star in the sky?

The brightest star in our sky is named Sirius. This is located in the constellation Canis Major. This constellation is also called the Great Dog and hence the star is also known as the Dog Star.  Because of its brightness, the Greeks called it scorching which is the origin of the word Sirius. Ancient astronomers noticed that Sirius rose with the sun late in the summer. And the hot days of late summer were given the name dog days. The Egyptians worshipped this star as a god who helped farmers because, before the season of the Nile river floods, this star was seen in the mornings.

Actually, Sirius is no brighter than many of the other stars in the sky; it appears bright to us because it is closer to the Earth than some other big stars. It is only about 8.5 light years away which means the light we see left Sirius 8.5 years ago.

Sirius is not a single star but a double star. Canopus is the second brightest star we see from the Earth. It is many times much brighter than Sirius but is very far away. 111 light years away and hence looks less bright.

What is the corona of the sun?

If you see a photograph of the sun during a total eclipse, you can see an uneven glow of light all around the eclipse sun. This is called the corona.

The surface of the sun is not solid but is composed of hot gases. In fact, the sun is surrounded by four layers of gaseous matter that hide what is underneath. The outermost layer is called the corona. The next three are known as the chromosphere, the reversing layer, and the photosphere.

The chromosphere or the color sphere is about nine thousand miles thick and is made up mostly of hydrogen and helium gases. At the time of the total eclipse, it shines around the dark disc with a brilliant scarlet light. From this red border, flame-coloured clouds of the same material shoot out to great distances, sometimes even as long as a million miles. They look like huge irregular flames of fire.

The outermost layer of r the corona is made of light, gaseous matter. It has two parts; the inner one is close to the red chromosphere and is a band of pale yellow. The outer one is white, with streamers extending out millions of miles. It is normally difficult to see and study the sun and its layers. The best time to photograph and see the corona and the chromosphere is the time of total eclipse.