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John Evershed (1911 - 1923) : [142]

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JOHN EVERSHED 1864 – 1956
  • Born on February 26, 1864 at Gomshall in Surrey, Evershed was educated privately and started to work in the chemical industry. At an early age he developed an interest in astronomy and established his own observatory at Kenley in Surrey in 1890. In 1906 he was appointed the assistant director of the Kodaikanal Observatory. In 1911 he succeeded Michie Smith as the director and at Kodaikanal he continued his work on prominences and with Mrs Evershed he published an important memoir on the distribution of prominences during the course of a solar cycle. Evershed had considerable experience of astronomical work before he joined Kodaikanal Observatory. Soon after his arrival here he took up a systematic study of the spectra of sunspots using two high dispersion grating spectrographs. On 7 January 1909 he made an outstanding discovery relating to sunspots, now known as ‘Evershed Effect’. His discovery revealed a radial motion of matter in the penumbral region of Sunspot – a result that was totally unexpected. This work, published in 1909, led to his election to the Royal Society in 1915 and to the award of the Gold Medal of the Royal Astronomical Society in 1916. Evershed also greatly improved the quality of the Spectroheliograms obtained at the Observatory. Another line of work to which Evershed and also Royds devoted considerable time and attention was the accurate measurement of the minute displacements of the solar absorption lines and the corresponding lines in the laboratory arc Spectra. Their intension being to clock the gravitational red shifts predicted from the general theory of relativity. Soon after his arrival in 1907, Evershed discovered the ultraviolet tail bands in Comet Daniel that are now described to CO+. Evershed made numerous studies of the planet Venus and of Nova Aquilae 1918. And his high dispersion spectra of Sirius have had the highest dispersion values employed in stellar spectroscopy until recently. While at Kodaikanal, he greatly improved the quality of the equipment of the Observatory, designing and building a large Spectrograph using a 5 – inch grating by Michelson.

     

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