ASTRONOMY

Centenary of a solar observatory

The Kodaikanal Observatory will celebrate its centenary in the coming months with scientific colloquiums and other events.

T.S. SUBRAMANIAN
in Kodaikanal and in Bangalore

DAY after day for close to 95 years now, as sure as the sun rises in the eastern sky each morning, a six-inch telescope at the Kodaikanal Observatory has been photographing the sun's spots from its perch in the rarefied heights of the Western Ghats. Thes e images, captured by one of the world's oldest extant telescopes, provide invaluable data to astronomers the world over - many of whom will gather in Kodaikanal later this year for the celebrations to mark the centenary of the observatory.

The Indian Institute of Astrophysics (IIA) has drawn up big plans to celebrate the centenary over the next few months. An International Astronomical Union colloquium is being organised, and about 50 scientists from abroad are expected to participate in i t. Further, specialised seminars would be held in Bangalore, Ladakh and Kavalur (Tamil Nadu), according to IIA Director Prof. Ramanath Cowsik. The IIA will also install the world's highest-altitude telescope, a two-metre infrared and optical telescope, a t Hanle in southeastern Ladakh, at an altitude of 15,000 feet. "It will be a national and international celebration, and the Kodaikanal Observatory will be the fulcrum of the activities," Cowsik said.

The Kodaikanal Observatory, which is one of only three solar observatories that are more than 75 years old (the other two are at Meudon in Paris and at Mount Wilson in the United States), has a notable history. According to Prof. Rajesh K. Kochchar of th e IIA, who has written several papers on the history of the Kodaikanal Observatory and other observatories in India, the Madras Observatory, which was set up in 1786, was Kodaikanal's predecessor. In a paper titled "The Growth of Modern Astronomy in Indi a, 1651-1960", published in 1991 in Vistas in Astronomy (Vol.34, pp.69-105), a science journal published from England, Kochchar wrote that in 1786, William Petrie, an "influential civil servant" and an astronomer, "set up an iron-and-timber observ atory at his 11-acre residence at Egmore, Madras, and furnished it with his own instruments." This signalled the beginning of the Madras Observatory.

According to Kochchar, on May 19, 1790, "the Court of Directors (of the East India Company) decided to accept Petrie's offer and to establish an observatory for 'promoting the knowledge of Astronomy, Geography and Navigation in India'."

DAVID GEORGE
The Kodaikanal Observatory, which boasts of one of the world's oldest extant telescopes.

He wrote: "In 1791, a garden house was purchased at Nungambakkam, Madras, while the instruments were removed to the Fort because of the war against Tipu, Sultan of Mysore... A separate 20 ft x 40 ft single room was constructed in 1792 as the Observatory. "

In 1891, after the death of Norman Robert Pogson, who was the Director of the Madras Observatory for 30 years, the question of building a new observatory came up for consideration. This followed a famine in Madras Presidency, which underscored the need f or a study of the sun so that monsoon patterns could be better understood. Kochchar wrote: "Thanks to the efforts of John Eliot, Meteorological Reporter to the Government of India (the post was later renamed Director-General of Observatories), it was fin ally decided in 1893... to establish a solar physics observatory at Kodaikanal in the Palani Hills of South India with the Madras Astronomer Charles Michie Smith as the Director; to transfer all astronomical activity from Madras to Kodaikanal; and to pla ce the new observatory under the control of the Central Government." The Kodaikanal Observatory came into existence on April 1, 1899.

In another paper, titled "Kodaikanal Observatory: Instruments and Buildings", which was presented during the bicentenary of the Madras Observatory in 1987, Kochchar wrote: "In 1895, the 100-acre observatory site was taken over, a road was built to the to p of the hill, and material collected for the Director's residence. In October 1895, the foundation stone of the Summit Hall (which is today called the Main Hall)... was laid by Lord Wenlock, the Governor of Madras, even though the building would not be ready for another four years. In July 1897, Michie Smith laid the north-south line, and in December that year, work on the building was begun." Then, the foundation for the Director's residence was laid. On moving to his residence in February 1899, Michi e Smith's first task was to complete the Main Hall, atop the Nadingapuram hill.

DAVID GEORGE
At the museum at Michie Smith Hall, panels depicting solar images recorded at the observatory. The plates of solar images at the observatory provide invaluable data to astronomers the world over.

According to the official Annual Report for the Madras and Kodaikanal Observatories for 1899-1900, "As soon as the towers for the domes were ready, the Director personally undertook the erection of the domes. As no skilled workmen were provided, he had w ith his own hands to do all the work that could not be done by a common native village carpenter or blacksmith. This included the driving of some 2,300 rivets. Both the domes were... completed by December. Before this time, the whole of the buildings had been roofed in, and the laboratory and computer's room were in use."

THE two domes of the Main Hall house the six-inch solar telescope, which is still in use, and an eight-inch stellar telescope, which is no longer in use. Another building in the Kodaikanal Observatory houses a spectroheliograph for photographing the sun not only in calcium k spectral line but in hydrogen alpha. It has been in use since 1912. An inscription at the entrance to the building reads: "In this building, on January 5, 1909, John Evershed made the discovery of the phenomenon of radial motion in sun spots, that is now known as the Evershed effect."

In their book Astronomy in India, A Perspective(1995), a diamond jubilee publication of the Indian National Science Academy, New Delhi, Kochchar and Jayant Narlikar wrote: "The arrival of John Evershed in 1907 (as Assistant Director to begin with) heralded the Observatory's golden age. Choosing to come to India, no doubt to work in solitary splendour, Evershed made Kodaikanal into a world-class, state-of-the-art observatory."

The Kodaikanal Observatory also has a 20-inch telescope, which came in 1912 from Pune when the Maharaja of Bhavnagar Taktasinhji Observatory was closed down; an ionospheric laboratory, from where the earth's ionosphere is continuously observed with the h elp of an ionosonde; a solar tunnel telescope acquired in 1958, in which mirrors in a 11-metre-high tower direct sunlight into a 60-metre-long underground tunnel, where a lens forms a stationary image of the sun, 34 cm in diameter and showing in fine det ail the solar features; and a museum in what was Michie Smith's residence.

The pride of place, however, goes to the six-inch telescope, installed at the entrance to the Main Hall. The images of sunspots that it has captured for close to 95 years go to make up an invaluable collection of plates which are stored in the plate vaul t of the Main Hall. The telescope has a lens through which sunlight streams in and photographs of the "white light" (which comprises the seven colours of the rainbow) of the sun are taken, day after day. These photographs show the surface of the sun with sunspots. Sunspots are darker than the surrounding areas because the temperature at sunspots is lower than that in their surroundings. Sunspots are regions of high magnetic field. According to IIA scientists, these magnetic fields make the sun an intere sting object of study. Once in 11 years, the number of sunspots increase; once in 11 years, their number declines. The number of sunspots is expected to increase between June 2000 and December 2001.

DAVID GEORGE
Prof.Ramanath Cowsik, Director of the Indian Institute of Astrophysics.

According to IIA scientists, the Kodaikanal Observatory also studies solar flares, which are sudden bursts of energy in the plages of the chromosphere of the sun when high magnetic fields develop. The flares release charged particles at very high speed, which travel to the earth's atmosphere. This phenomenon is called coronal mass ejection. In the earth's ionosphere, the particles affect radio communication. Solar flares can debilitate satellites and power transformers.

The scientific community looks ahead to the centenary celebrations with the hope that the deliberations and the media attention they will generate will provide an impetus to solar studies and the good work being done at the Kodaikanal Observatory.