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A depiction of the sun, and its six nearest planets: Mercury, Venus, Earth (show with moon), Mars, Jupiter, and Saturn.

In cosmology, sun (TR:591) (LH:21) (TL:612) is the star about which the earth rotates.


The sun by mass composition is 71% hydrogen, 27% helium, 1% oxygen, and 64 to 68 others elements in rarer amounts.[1] The reaction of hydrogen H with each other to produce helium He, the reaction of which shown below, is what makes for the heat and light output of the sun:


In particle terms, four protons combine into a new nucleus, during which time two of the protons transform into neutrons, two of the electrons are turned into photons, which we see as light

4 (   ) →   + heat + light

and the difference in mass between the products (one He) and reactants (four H) is:

m = 0.048 x 10-27 kg

This mass m, according to the mass-energy equivalence relation:


where E is the energy and c is the speed of light, is transformed into the following amount of energy:

E = 4.32 x 10-11 J

which multiplied by the mass of the sun is the heat felt on the earth.

Helium fusion

In 1920, Arthur Eddington, in his “The Internal Constitution of Stars”, after dismissing the “contraction hypothesis” model of the sun’s energy, e.g. as advanced by William Thompson, stated the sun’s energy comes from hydrogen transmuting into helium; the gist of which is as follows:[2]

“A star is drawing on some vast reservoir of energy by means unknown to us. This reservoir can scarcely be other than the sub-atomic energy which, it is known, exists abundantly in all matter; we sometimes dream that man will one day learn how to release it and use it for his service. The store is well-nigh inexhaustible, if only it could be tapped. There is sufficient in the sun to maintain its output of heat for 15-billion years. Certain physical investigations in the past year, which I hope we may hear about at this meeting, make it probable to my mind that some portion of this sub-atomic energy is actually being set free in the stars. Francis Aston's experiments seem to leave no room for doubt that all the elements are constituted out of hydrogen atoms bound together with negative electrons. The nucleus of the helium atom, for example, consists of four hydrogen atoms bound with two electrons. But Aston has further shown conclusively that the mass of the helium atom is less than the sum of the masses of the four hydrogen atoms which enter into it; and in this, at any rate, the chemists agree with him. There is a loss of mass in the synthesis amounting to about 1 part in 120, the atomic weight of hydrogen being 1.008 and that of helium just 4. I will not dwell on his beautiful proof of this, as you will, no doubt, be able to hear it from himself. Now mass cannot be annihilated, and the deficit can only represent the mass of the electrical energy set free in the transmutation. We can therefore at once calculate the quantity of energy liberated when helium is made out of hydrogen. If 5 percent of a star's mass consists initially of hydrogen atoms, which are gradually being combined to form more complex elements, the total heat liberated will more than suffice for our demands, and we need look no further for the source of a star's energy.”

In 1937, George Gamow and Carl Weizsacker proposed that the sun's energy was the result of a proton-proton chain reaction, wherein two protons p react to form a deuterium D, a positron e+, an electron neutrino  , releasing 1.42 mega electron volts of energy in the process:

  +   + 1.442 MeV

In 1939, Hans Bethe, building on this proton-proton reaction model, showed how similar reactions in stars could produce elements sized up to nitrogen, carbon, and oxygen.

In 1946, Fred Hoyle, in his “The Synthesis of the Elements from Hydrogen”, outlined how all the elements of the periodic table can be obtained from a process of “stellar nucleosynthesis” operating inside of stars.[3]

The following is a diagram of the 1948 Gamow-Alpher big bang nucleosynthesis model of the origin of hydrogen.[4]

In 1948, Gamow, and his PhD student Ralph Alpher, in their “The Origin of the Chemical Elements”, outlined a so-called “big bang nucleosynthesis” model of the origin of first elements, according to which the original “primordial matter” of the universe consisted of hot highly compressed neutron gas, or “overheated neutral nuclear fluid”, which started to decay into protons and electrons when the gas pressure fell down as the result of the expansion of the universe.[5]

“As pointed out by Gamow (1946), various nuclear species must have originated not as the result of an equilibrium corresponding to a certain temperature and density, but rather as a consequence of a continuous building-tip process arrested by a rapid expansion and cooling of the primordial matter. According to this picture, we must imagine the early stage of matter as a highly compressed neutron gas (overheated neutral nuclear fluid) which started decaying into protons and electrons when the gas pressure fell down as the result of universal expansion. The radiative capture of the still remaining neutrons by the newly formed protons must have led first to the formation of deuterium nuclei, and the subsequent neutron captures resulted in the building up of heavier and heavier nuclei.”

Here is another diagram of this:[6]


End matter

See also


  1. Composition of the sun – HyperPhysics.
  2. Eddington, Arthur. (1920). “The Internal Constitution of Stars”, Nature, 2653(106):14-20 Sep 2.
  3. Hoyle, Fred. (1946). “The Synthesis of the Elements from Hydrogen” (abs), Monthly Notices of the Royal Astronomical Society, 106(5):3343-83, Oct.
  4. Siegel, Ethan. (2014). “Why did the Universe start off with Hydrogen, Helium, and not much else?” (Ѻ),, Jan 8.
  5. (a) Alpher, Ralph; Gamow, George. (1948). “The Origin of the Chemical Elements” (pdf), Letter to the Editor, Physics Review, 73(7):803-04, Apr 1.
    (b) Alpher-Bethe-Gamow paper – Wikipedia.
  6. Klesman, Alison. (2019). “How did the first element form after the Big Bang?” (Ѻ),, Jan.

External links

  • Sun – Hmolpedia 2020.