TOTAL SOLAR ECLIPSE – 22 July, 2009

TOTAL SOLAR ECLIPSE – 22 July, 2009
Dr. Debiprosad DuariDirector, Research & AcademicM. P. Birla Planetarium, Kolkata
A rare and spectacular celestial event will be experienced on 22nd July, 2009. For every Indian, it will be an opportunity to see a solar eclipse at the early morning hours of the day. But, for people present within a patch of land, roughly around 258 km wide and stretching from the western coast of India in Gujrat to the north-eastern tip in Arunachal Pradesh it will be a total solar eclipse. The eclipse is an extremely rare one since the next time a full total solar eclipse that will be seen from the Indian subcontinent will be only on 3rd June, 2114. Though, there will be another total eclipse that will technically touch India in 2034, but it will be just over the inhospitable northernmost tip of Kashmir. So, after 22nd July, 2009 one has to wait another 105 years to see the fascinating beauty of an eclipsed sun.
A solar eclipse happens when the Sun, Moon and the Earth comes in a straight line. One can then expect that at every new moon a solar eclipse will occur, but this does not happen since the orbital plane of the moonaround the earth and the orbital plane of the earth around the sun is tilted at one another at an angle of 5 degrees, and only when the three bodies comes along the line of intersection of these two planes a solar eclipse takes place. The shadow of the moon has two distinct regions, one is called the umbra – which is a conical shaped area where the shadow is darkest and no light from sun can reach this region, the other is called the penumbra, where light rays from the sun partially illuminates the shadowed region. Only when the tip of the umbral cone touches a particular region on the surface of the earth, the people in that region experiences a total solar eclipse, whereas, the penumbral shadow falling on earth, produces a partial eclipse for the people observing the eclipse from the partially shadowed portion. Though any eclipse is an interesting phenomenon, but, the beauty of a total eclipse surpasses any of the experiences of a partial one. The tip of the umbral cone touches a particular area with the daybreak and ends up in another point on the earth just as the sun sets. The path of totality can cross continents and oceans in a curved path because of the spherical nature of the earth.
On 22nd July, 2009, the total eclipse starts at the western coast of India with the sun rising over the Gulf of Cambay and then the path of totality will pass over certain parts of Gujrat, Madhya Pradesh, Uttar Pradesh, Bihar, West Bengal, Assam, Arunachal Pradesh in the Indian mainland. Then onwards the umbral shadow will pass over Mynamar, China, through the south Japan Sea and will end over the Pacific Ocean near Kiribati Islands. A partial eclipse will be seen from all parts of India and certain parts of East Africa, Asian mainland, north eastern Australia and a small part of New Zealand. The uniqueness of this particular solar eclipse is that, it will be of the longest duration in this century. At the maximum, the total eclipse will continue for 6 minutes 39 seconds over a region on the Pacific Ocean. In India, within the region from where the total eclipse will be visible, the duration of the eclipse will be, on an average three and half minutes, with the maximum being at Coochbehar in northern part of West Bengal, where it will be for 3 minutes 53 seconds.
For the huge number of enthusiasts who have already made plans to be present near the path of totality to observe the total eclipse one big concern is that of cloud. Because of the rainy season, there is a distinct possibility that presence of clouds can mar the excitement of observing the total eclipse. Given by some of the statistics, a huge population will be converging on Patna for the eclipse, since the possible cloud cover is predicted to be less over Patna than other places. But, this do not mean, that from other places it will not be seen. One has to depend upon his/her own luck for the skies to be cloud free during the time of totality. Since the eclipse will be happening in the morning hours the altitude of the eclipsed sun will be quite low and so those interested to observe, has to find a place from where the eastern horizon is relatively free of any obstructions.
One has to be very cautious in observing a solar eclipse. When the eclipse is in its partial phase, one should not look at the partially eclipse sun directly. The best way to observe is to either see the phenomenon through a Nos. 14 Welder’s Glass, or aluminized Mylar filter which cuts down the intensity of the sun’s glare considerably. The other option can be, to project the image of the sun on a clean surface and it will allow any people to see the event at the same time. Enthusiasts can make pin holes and project the sun onto a plain surface and observe the projected image of the sun. Only during totality, when the sun is completely obscured by the moon, one can look directly at the totally eclipsed sun.
Most of the people who have earlier experienced viewing a total solar eclipse have described it as a lifetime experience. Specially, moments before and after the totality sets in, there are a series of dramatic events. Around a minute before the totality, if one is lucky, the shadow bands can be seen. These are ripples of light and shadows which can be viewed on a flat, light coloured surface and is believed to be caused by turbulence in the atmosphere. Near totality one can expect to see the formation of Bailey’s beads, the sun looks like a necklace beaded with pearls! This happens when light from the sun passes through the valleys on the surface of the sun, thus creating this pearl drop effects. The next event one can experience is the famous diamond ring effect, which happens because of the last rays of sun, before getting totally blocked by the moon passes through the region between two highlands on the lunar surface. Just as the totality begins, scientists have seen what is known as flash spectrum, which scientifically is quite important. One has to remember that the presence of helium was discovered by seeing the flash spectrum of the Sun during total eclipse from India. If someone is viewing the totality through a telescope or a high powered binocular, they can also see, or, photograph the pink glow around sun called the chromosphere and sudden eruption of solar flares. With proper photographic techniques one can also capture the beautiful corona, a region of pearly white radiation coming out of the sun during the totality.. During the totality, the surrounding become dark and one can perceive a distinct fall in temperature. Altogether it’s a memorable experience for anyone to view a total solar eclipse.
One can only wish luck to sky enthusiasts and general public, some of whom have made preparations long back to view this total eclipse on 22nd July, 2009 and hope that clouds will not play spoilsport for one of the most interesting and beautiful celestial phenomenon to be experienced by humans.
Photo: Courtsey NASA