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What are the Earth and Sun made of?

The earth consists mainly of the following chemical elements (as a percentage by mass):

  • Oxygen (O): about 46.6%
  • Silicon (Si): about 27.7%
  • Aluminum (Al): about 8.1%
  • Iron (Fe): about 5%
  • Calcium (Ca): about 3.6%
  • Sodium (Na): about 2.8%
  • Potassium (K): about 2.6%
  • Magnesium (Mg): about 2.1%
  • Other elements: makeup about 1.5%

The sun, like a star, is made up primarily of hydrogen (H) and helium (He). As a percentage by weight:

  • Hydrogen (H): about 74.9%
  • Helium (He): about 23.8%
  • Other elements (including heavy elements): about 1.3%
  • Figures from different sources may vary slightly.

Wasn’t it always like this?

Arthur Eddington is an English astrophysicist and astronomer. One of his most famous and significant expeditions was an expedition to the island of Príncipe (West Africa) during a solar eclipse on May 29, 1919. This expedition made successful observations, and the results of the expedition confirmed Albert Einstein’s theory of relativity.

In his famous monograph The Internal Constitution of the Stars, Arthur Edington suggested that the composition of stars and the Sun is dominated by heavy elements – oxygen, silicon, aluminum, and even iron.

Cecilia Payne – an American astrophysicist established the composition of the sun and stars. Her research differed from the conventional view. Edington agreed with her that hydrogen could dominate the surface of stars, but went no further.

Sessilia, working under the guidance of Harlow Shapley, studied a huge number of stellar spectra and found that stars are mainly composed of hydrogen and helium, and not of heavier chemical elements.

A hundred years ago, these data were not known to anyone, incl. Edington. Astronomers of the time considered it impossible for hydrogen to exist in the universe on such a scale. They initially did not believe the 25-year-old graduate of the University of Cambridge Cecilia Payne, who was the first to understand which atoms dominate the universe.

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