Pioneer of solar astronomy: Who is Charles Greely Abbot?

(1872-1973) US astrophysicist. He developed the pyrheliometer used in the measurement of solar temperature and determined the value of the solar constant. He was born in Wilton, New Hampshire. From 1928 to 1944 he was director of the Smithsonian Astrophysical Observatory in Washington, under the direction of the Smithsonian Research Foundation. During this mission, Abbot focused his work on solar astronomy and developed various methods and tools to measure the Sun's radiation and temperature. He died in Washington.

Charles Greeley Abbot (May 31, 1872 – December 17, 1973) was an American astrophysicist and the fifth secretary of the Smithsonian Institution, serving from 1928 until 1944.

While solar astronomy made great advances in the 19th century, the measurement of the "Sun" temperature was still one of the most difficult problems to be solved. The biggest factor in the failure of this measurement, which seems easy in principle, is the absorption property of the atmosphere. The sun emits energy in many different wavelengths, ranging from X-rays to radio waves. In 1881, for the first time, a solution to the temperature measurement problem was introduced, and it was thought that by determining the intensity of radiation at each wavelength separately, the Sun's temperature could be determined from the sum of all values. Abbot's most important contribution to this field is the determination of the distribution of energy in the solar spectrum to different wavelengths. While studying solar radiation and spectrum, he measured the solar constant, which was the only data at that time to find the value of the Sun's temperature. The approximate value of this constant, which is defined as "the total radiant energy per unit area of a theoretical surface on the Earth, at an average distance from the Sun and receiving the Sun's rays perpendicularly," is 1.9 cal/cm2/min.

In the Pyrheliometer developed by Abbot to measure the temperature of the Sun, the sun's rays are dropped on a silver plate and the value of the radiation is measured with a very sensitive thermometer.