Environment & Biodiversity

125 Years of Kodaikanal Solar Observatory

This year marks the 125th anniversary of the Kodaikanal Solar Observatory (KoSO).

About Kodaikanal Solar Observatory (KoSO)

  • The notion for an Indian solar observatory arose in the late nineteenth century, with the then-government approving the creation of the Solar Physics Observatory in Kodaikanal in August 1893.
  • Following Charles Michie Smith’s surveys, Kodaikanal in Tamil Nadu’s Palani hills was chosen as the site for the observatory due to its favourable atmospheric conditions.
  • Lord Wenlock, the then-Governor of Madras, laid the foundation stone for KoSO in 1895.
  • The systematic observations at KoSO began on March 14, 1901.
  • KoSO was originally designed to house solar observation instruments, such as telescopes for studying sunspots, prominences, and solar radiation.
  • KoSO currently houses modern instruments such as the H-alpha telescope and the White Light Active Region Monitor (WARM) for high-resolution solar imaging.

Historical Perspective

  • Ancient Legacy: Seafarers, mathematicians, astronomers, and physicists have spent centuries studying the Sun and its celestial phenomena.
  • British Era Initiatives: In 1792, the British East India Company erected the pioneering Madras Observatory, which was a watershed moment in regional astronomy research.
  • Madras Observatory Legacy: The Madras Observatory logged important astronomical observations between 1812 and 1825, establishing the groundwork for solar research in India.
  • Switch to systematic observations: Dedicated solar observations began in 1878, promoting a better understanding of solar phenomenon.
  • Methodological advancements: The use of systematic observational techniques enabled more complete and detailed investigations of the Sun’s behaviour. 

Need for such an observatory

  • The Great Drought of 1875-1877: This event, caused by insufficient rainfall, prompted the need for extensive solar studies to understand its effects on weather patterns.
  • India’s Geographical Significance: India’s drought was part of a bigger global phenomena that affected other nations and resulted in widespread hunger.
  • Scientific Inquiry: Scientists recognised the possible importance of solar variability in influencing climatic patterns, motivating research into the Sun’s behaviour and its relationship to environmental events.

Scientific endeavours of KoSO

  • The observatory provided significant discoveries to solar physics, notably the discovery of the Evershed Effect, which describes the radial motion of sunspots.
  • Over time, KoSO’s scientific interests evolved beyond solar physics to encompass cosmic rays, radio astronomy, ionospheric physics, and star physics.
  • KoSO was transferred from the India Meteorological Department (IMD) to the Indian Institute of Astrophysics (IIA) in Bengaluru in April 1971.

Repository for the KoSO

  • From 1904 to 2017, all sun observations were documented on photographic films and plates.
  • A new telescope equipped with CCD cameras took over and has been observing the Sun since 2017.
  • Prof J C Bhattacharyya began digitising the documents in 1984, and others have continued the task.
  • KoSO currently has a digital collection of 1.48 lakh solar photos, totaling 10 terabytes of data.
  • These comprise 33,500 white-light photos (showing sunspots), 45,000 Ca II K spectral line images (revealing plages), and 70,000 H-alpha photographic plates (showing prominences).

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