ON WEDNESDAY, July 22, 2009 an exceptionally long duration total eclipse of the Sun will be visible in the eastern part of the globe. The path of the Moon’s umbral shadow begins in India and crosses through Nepal, Bangladesh, Bhutan, Myanmar and China. The instant of greatest eclipse occurs in the Pacific Ocean at 02:35:19 (UT). The maximum duration of totality here will be 6m39s. In Assam the eclipse will start around 5:30 am and will end around 7:40 am. The totality will be around 6:30 am in lower Assam and around 6.31 am in upper Assam. The duration of totality will vary from place to place. Guwahati being on the latitude of 26011’ (N), will be just out of the southern limit of path of totality at 26013’ (N). The northern limit here will be at 27054’ (N) and the width of path of totality will be around 225 km in Assam, Bhutan and Arunachal Pradesh. The totality will begin around 6:30 am in this region. The central line between northern and southern limit will have maximum duration of totality. Pasighat in Arunachal Pradesh is just south of central line in path of totality. Places away from central line on either side will have lesser time of duration of totality. (Places on either side of path of totality will see only partial solar eclipse.) Dhubri in the west and Dibrugarh towards east in Assam, although will be inside the path of totality, will have lesser duration of 2 minutes 41 seconds and 3 minutes 38 seconds respectively as both the places are away from central line.

Total eclipses of the Sun draw solar astronomy enthusiasts to the far corners of the globe. Amateurs are attracted by expectations of the breathtaking beauty of the eclipsed Sun during the few minutes of totality. The sky is then as dark as twilight. Only in the darkness of totality, the solar corona, the outer atmosphere of the Sun, can be viewed with the unaided eye. A total eclipse of the Sun is one of the grandest natural phenomena and the most spectacular celestial event. A total eclipse of the Sun occurs when the Moon passes between the Sun and the Earth and obscures the Sun completely.

A total eclipse, which is a life time experience, is a fascinating phenomenon — our Sun, which is so normally so reliable, is suddenly stained black by the Moon. Any solar eclipse is an interesting event, but a total solar eclipse is the most spectacular astronomical phenomenon that you’ll ever see.

During the last 500 years, only three total solar eclipses (TSEs) had swept Assam. The TSE of 17.10.1762 swept Barak Valley. The eclipse of 04.06.1788 swept Brahmaputra valley and third one on 17.07.1814 touched Arunachal Pradesh and Dibrugarh, Tinisukia in Brahmaputra Valley. In the last century, three total solar eclipses occurring in 1980, 1995 and 1999 were visible from Indian soil. However, totality of none was visible from the Northeast. The total solar eclipse occurring on July 22 will dramatically pass over Assam, Bhutan and Aruanachal Pradesh in morning, starting from Gujarat. The duration of totality in central line in the northeastern region will be more than four minutes, the longest duration in recent times.

Prominent places like Dhubri, Kokrajhar, Bongaigaon, Pathsala, Barpeta, Sarthebari, Tihu, Nalbari, Rangia, Tangla, Kalaigaon, Mangaldai, Kharupetia, Rowta, Udalguri, Dhekiajuli, Tezpur, Balipara, Jamuguri, Sootea, Bishanath Chariali, Gohpur, Narayanpur, Banderdewa, Bihpuria, Laluk, North Lakhimpur, Gogamukh, Dhemaji, Silapathar, Jonai, Murkongselek, Sivasagar, Dibrugarh, Tinisukia, Doomdooma, Digboi, etc in Assam will be very convenient to observe the event. All these places will be within the path of totality and few of them more or less closer to the central line. In the Northeast, the central line will pass through mostly hilly region making it difficult to observe the TSE from such terrains. As the eclipse will occur in morning, the elevation of the Sun during totality in lower Assam will be only about 200. In places like Dibrugarh, Tinisukia, the Sun’s altitude will be around 260 during totality.

A total solar eclipse is dramatic event. The sky begins to darken, the air temperature falls, the winds increase as the Moon’s umbra races towards us. Everything in nature responds; the birds go to roost, flowers close their petals, crickets begin to ring as if evening had occurred. As totality approaches, the landscape is bathed in shimmering bands of light and dark and the last few rays of sunlight peak out from behind the edge of the Moon. And finally pearly white corona blazes forth in a star-studded midday sky. It is an awesome sight.

The total phase of the eclipse is accompanied by the onset of rapidly darkening sky whose appearance resembles evening twilight about half an hour after sunset. The effect presents an excellent opportunity to view planets and bright stars in the daytime sky. The brightest and most conspicuous planet will be Venus. It is located in Taurus. During the totality on July 22, the Sun’s background constellation will be Cancer near its border with Gemini.

Solar eclipses result from the alignment of the Sun, Moon, and Earth on the day of New Moon. Total solar eclipses — in which the Sun is completely blocked by the Moon — are a spectacular and rare sight to witness. It is the most beautiful celestial event in the sky. The total phase of an eclipse can and should be seen without any filter. It is completely safe to do so. Certainly the most spectacular and awe-inspiring phase of the eclipse is totality. Photograph of the corona must be made without filter.

A solar eclipse offers students a unique opportunity to see a natural phenomenon that illustrates the basic principles of mathematics and science taught in school. Indeed many scientists (including astronomers) have been inspired to study science as a result of seeing a total solar eclipse. The rise and fall of environmental light levels during an eclipse illustrates the principles of radiometry and photometry, while biology classes can observe associated behaviour of plants and animals. It is also an opportunity for school children to contribute actively to scientific research — observation of contact timings at different locations along the eclipse path is useful in refining our knowledge of the orbital motions of the Moon and the Earth and sketches and photographs of the solar corona can be used to build a three-dimensional picture of the Sun’s extended atmosphere during the eclipse.

The partial phases of the total solar eclipse up to the display of ‘Diamond Ring’ or any partial or annular solar eclipses must be observed with proper solar filter only. The totality can be observed directly without any aid. It can also be photographed easily without any filter. The brightness by corona is slightly more than brightness of a full moon. As soon as totality ends, again filter should be used to protect our eyes. We should feel fortunate enough to have a longest duration total solar eclipse in our life time. There will not be any total solar eclipse over Assam in the next 900 years.

As the event will be occurring in the monsoon period, chance of enjoying the eclipse depends upon availability of clear sky in the morning of July 22, 2009. Doordarshan can arrange live telecast of the event from Dibrugarh University campus since Dibrugarh will be the most ideal place for observation in the south bank of Brahmaputra.

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