125 Years of Kodaikanal Solar Observatory

The Kodaikanal Solar Observatory (KoSO) is a solar observatory located in Kodaikanal, Tamil Nadu. Established in 1899, it is one of the oldest solar observatories in the world and has been at the forefront of solar research for over 125 years. The observatory, which celebrates its 125 years of existence, is currently operated by the Indian Institute of Astrophysics (IIA), Bengaluru.


The need for a solar observatory in India was first recognized in the late 19th century, following the Great Drought of 1876-1878. The Madras Observatory, established by the British East India Company in 1792, had been recording astronomical observations, but a dedicated solar observatory was deemed necessary to study the relationship between solar activity and India’s monsoon patterns.

In 1893, the British Government sanctioned the establishment of a Solar Physics Observatory under the meteorological budget. The site selection process, led by Charles Michie Smith, a professor at Madras Christian College, eventually chose Kodaikanal as the ideal location due to its favorable weather conditions and clear skies.

The observatory’s foundation stone was laid in 1895 by Lord Wenlock, the then Governor of Madras. Regular observations began on March 14, 1901, with Charles Michie Smith serving as the first director of KoSO.

Instruments and Observations

Over the years, KoSO has housed several important instruments, including:

  • Bhavnagar Telescope: A 16-inch Newtonian/Cassegrain telescope, which was the largest in India from 1888 to 1968.
  • Spectroheliograph: Used for studying the Suns chromosphere and prominences.
  • H-alpha Telescope: For full-disc imaging of the Sun.
  • White Light Active Region Monitor (WARM): Enables simultaneous observations of the photosphere and chromosphere.

The observatory has made significant contributions to solar physics, including:

  • The discovery of the Evershed effect by John Evershed, who served as the director of KoSO from 1911 to 1922.
  • Regular sunspot observations and measurements of solar radiation.
  • Spectroscopic studies of the solar chromosphere and prominences.

Digital Archive

KoSO maintains a vast archive of solar data, with observations spanning over a century. In recent years, the observatory has undertaken a digitization project to preserve and make accessible its valuable collection of solar images.

  • The digital archive contains over 1.48 lakh digitized solar images, amounting to 10 terabytes of data.
  • The collection includes 33,500 white-light images of sunspots and thousands of other solar images recorded daily since the early 20th century.

KoSOs digital archive is one of the most comprehensive and longest-running solar data collections in the world, with a coverage of more than 75% of the period.

Current Status and Research

Today, KoSO continues to be a premier institution for solar research in India. The observatory is equipped with state-of-the-art instruments and is actively involved in various national and international collaborations.

Some of the current research areas at KoSO include:

  • Solar activity and its impact on space weather
  • Study of solar flares and coronal mass ejections
  • Investigation of the solar magnetic field and its evolution
  • Solar-terrestrial relationships and their influence on Earths climate

The observatory also plays a crucial role in training and education, hosting workshops, and providing research opportunities for students and scientists from India and abroad.



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