125 Years of Kodaikanal Solar Observatory

Nestled in the Palani Hills of Tamil Nadu, the Kodaikanal Solar Observatory (KSO), established on 1 April 1899, has been a leading centre for solar research in India for over a century. Operated by the Indian Institute of Astrophysics, this longest-running astronomical observatory in the country boasts one of the world’s longest continuous daily records of the Sun. Originally an extension of the Madras Observatory (est. 1792), KSO’s focus shifted exclusively to solar observation in Kodaikanal due to its strategic high-altitude location (2,343 metres), which offered optimal atmospheric conditions.

Nestled in the Palani Hills of Tamil Nadu, the Kodaikanal Solar Observatory (KSO), established on 1 April 1899, has been a leading centre for solar research in India for over a century. Operated by the Indian Institute of Astrophysics, this longest-running astronomical observatory in the country boasts one of the world’s longest continuous daily records of the Sun. Originally an extension of the Madras Observatory (est. 1792), KSO’s focus shifted exclusively to solar observation in Kodaikanal due to its strategic high-altitude location (2,343 metres), which offered optimal atmospheric conditions.

The Observatory’s contributions to solar physics are vast and varied. Researchers at the KSO have made pioneering studies of sunspots, solar flares, prominences, and the solar corona throughout its 125 years of operation. They have investigated the Sun’s magnetic field, activity cycles, and its impact on Earth’s climate. The KSO has also played a crucial role in developing advanced observational techniques and instrumentation for solar research.

The Observatory has meticulously recorded observations of the Sun’s photosphere and chromosphere on photographic plates and films for more than a century. To facilitate the study of historical solar activity, including sunspots, plages, filaments, and flares, these valuable records have recently been digitised, which has been made accessible to both national and international solar physicists.

Beyond solar physics, the KSO has made significant contributions to ionospheric research, and has helped us understand the complex interactions between the Sun and the Earth’s ionosphere, which has implications for radio communication and satellite operations.

As a primary centre for solar research in India and globally, KSO has trained many generations of Indian astronomers via innumerable workshops and schools. Strongly connected to the local educational community, KSO also features a modern astronomy museum that attracts approximately 50,000 tourists annually.

The Department of Posts is proud to release a commemorative stamp on 125 Years of Kodaikanal Solar Observatory. Recognising the legacy of the Kodaikanal Solar Observatory through this stamp is a fitting tribute to this key scientific institution of India, and serves as a reminder of India’s significant contributions to global science. The KSO has pioneered solar research, and its work remains vital today. By acknowledging the KSO, we highlight its role in shaping our understanding of the Sun and its impact on our planet. In conclusion, the Kodaikanal Solar Observatory is a national treasure that deserves to be celebrated for its rich history, scientific achievements, and enduring contribution to society.