Winter Solstice day 2007

Winter Solstice, Mars Close approach and the Jantar Mantar

This year, the winter Solstice falls at about 11:00 AM on the 22^nd of December. What exactly happens at this moment? The winter solstice for the Northern Hemisphere, is that time of the year when the Sun has gone the maximum angular distance from the Equator that it can. The sun rises way south of East, and sets way south of West. The day is the shortest and the night longest.

Following this moment is the Uttarayana or the Northward movement of the Sun. A few thousand years ago, the Uttarayana also coincided with the entry of the Sun into the Zodiacal constellation of Capricorn. Similarly, the Summer Solstice coincided with the entry of the Sun into the constellation of Cancer. This was the reason why these two constellations have found their reflections on the terrestrial globe as the Tropic of Cancer and the Tropic of Capricorn.

With the passage of time, the precession of the axis of rotation of Earth, has resulted in a shift in the relative positioning of the Sun, against the background Zodiacal constellations, in such a way, that the Winter Solstice does not anymore coincide with the entry of the Sun into the constellation Capricorn. The Sun actually enters Capricorn around the middle of January. The celebration of Makar Sankranti is related to the entry of the Sun into the constellation of Capricorn – although, to begin with, the celebration of Makar Sankranti must also have been related to the Winter Solstice or the Dakshinayana. The two were taking place at the same time, a few thousand years ago. Now, however, the Dakshinayana and the Makar Sankranti are displaced by a few days as a result of the prcession of the Earth’s axis of rotation over these few thousand years.

It is this very precession, which also ensures that the Zodiacal constellations that the newspaper astrological columns claim to represent your birthdate, are actually wrong. Is anyone bothered and would like to know why all the astrological predictions are irrelevant in any case?

If so, be at the Jantar Mantar, on the 22^nd of December, the Winter Solstice. Volunteers from Nehru Planetarium, New Delhi and the Amateur Astronomers Association, Delhi, will be present from 11:00 AM till evening, to help visitors understand the exact usage of the Jantar Mantar instruments and measure the position of the Sun in the sky, on that day.

The best place to appreciate the Winter Solstice, for the citizen of Delhi, is the Jantar Mantar.  The marble Niyat Chakra instruments of the Misra Yantra are very well suited for giving an easy understanding to people, about the annual movement of the Sun in the sky. The exact moment when the changeover takes place, between the Dakshinayana to Uttarayana (about 11:37 AM IST, 22^nd of December) can be appreciated by looking at the position of the shadow of the Sun, on the Niyat Chakra. At this moment, the position of the shadow of the Sun, on this scale, should be equal to 23.5 degrees towards the South of the 0 marking on the scale – be there at 11:00 AM in the morning and participate in observations to test this and get a feel for the instruments of the observatory and celestial movements!

There is more. The Jaiprakas, a bowl shaped instrument reflecting the sky, originally had markings to delineate the position of the Tropic of Capricorn. The team from the Nehru Planetarium will be placing temporary cross wires over the Jai Prakas bowls and tracing the position of the Sun throughout the day, in the bowl. This will mark the position of the Tropic of Capricorn in the bowl, as the Sun is at the corresponding position in the sky on this day. Remember, the Sun is not in the constellation of Capricorn in the sky, which has moved away from its location of a few thousand years ago. The Sun is still in Sagittarius, but, has reached the Winter Solstice point. The historical names for the Tropics continue, creating all this celestial confusion!

The Jaiprakas also had markings originally, that showed the entry of the Sun into a given Zodiacal sign or Rashi. The presence of these markings would be a very good alert for people to realize that there are these changing celestial positions all around them! Conducting observations from the Jantar Mantar, on such celestially interesting days would also bring the observatory alive as an Astronomy Laboratory where celestial movements can be easily understood – which was the intention of the original creator of these instruments – Raja Jai Singh!

The position of Mars in the sky, during its current close approach, can also be better appreciated by observing after sunset, from the Ram Yantra. In 2003, when Mars was the closest to Earth in thousands of years, it appeared substantially due South. This year, however, it has moved Northwards and goes higher up in the sky as the night advances. These differences in the relative positions of Mars can be better appreciated from the Ram Yantra of the Jantar Mantar Observatory.

All in all, it will be an interesting day to spend at the Jantar Mantar – the 22^nd of December, the Winter Solstice day.

Written By. N. Rathnasree, Nehru Planetarium, New Delhi.