High Celestial Drama - Longest Solar Eclipse of the 21st Century - July 22, 2009

The phenomenon of an eclipse is as old as the universe itself. In the olden days people did not realize that an eclipse was just a celestial phenomenon, but associated the occurrence of an eclipse with bad omens or the wrath of Gods. This is no longer the case and science understands the phenomenon of eclipses to a great extent. Still the craze and urge to see an eclipse is as strong as the fear and awe that must have existed in the days of the yore.

Basically the term eclipse refers to a situation wherein the light of a celestial object is partially or completely blocked by another object so that a shadow appears in its place. You might compare it to a light bulb and your hand projecting its image on the wall which seems quite a simple phenomenon but the grandeur of the event lies in its scale. We are not talking about petty objects or even giant structures here, but of complete planets and celestial bodies. You can take a look at the sketch below to understand this concept of a solar eclipse

We will only talk about eclipses which involve the Sun, Moon and the Earth. In this context, eclipses can be divided broadly into two types - solar eclipses and lunar eclipses. We will concentrate on the former here and leave the latter for separate discussion. A solar eclipse can be further subdivided into various sub-categories such as total solar eclipse, partial solar and annular eclipse.

The total solar eclipse occurs when the moon is positioned between the Sun and the Earth in such a manner that it completely obscures the visibility of the Sun from the Earth even if for a brief period of few minutes. This is a very spectacular sight to observe. But as luck would have it, such an eclipse is due on the July 22, 2009 which is very near at the time of writing this article (if you happen to read this article after this date, don’t worry for there be will other chances as well).

You might think that since the Moon is much smaller in size than the Sun, how can it totally cover the latter? Well if I may remind you that if the Sun is bigger than the Moon (infact much bigger), it is also located very far off from the Earth as compared to the Moon. Hence the apparent size of the two happens to be the same, whenever the Moon comes at a particular position during the cosmic cycle. At that brief point of time a total eclipse is evident in a narrow range of land on the Earth which is of the order of few hundred miles. The people in most other parts of the world see partial eclipse depending on their location on the planet. Look below at the spectacular image of a solar eclipse

This phenomenon is going to occur on July 22, 2009 and you can check out the NASA website for more details. This eclipse is going to be the longest ever in the past 2000 years so you can imagine the importance of this eclipse. Though this will pass through several countries of Asia including India, Nepal, Bhutan and Bangladesh, it will be best viewed from China and the picture below shows a map of the track of this eclipse passing through various parts of China. As you can see this track is a narrow belt which covers the whole of China and the total eclipse during this phase will be around 6 minutes which is really a long time even by astronomical standards. After that the eclipse would be directed southwards towards the Pacific Ocean

One last thing: In the excitement of watching the event do not forget the safety aspects of viewing the total solar eclipse (or any other solar eclipse for that matter). Your eyes are very important and delicate and should be protected from radiation effects of the sun by using appropriate vision aids for watching the eclipse.

http://eclipse.gsfc.nasa.gov/SEmono/TSE2009/TSE2009iau/TSE2009-fig03.GIF

http://eclipse.gsfc.nasa.gov/SEmono/TSE2009/TSE2009iau/TSE2009-fig01.GIF