According to one hypothesis about a source of energy that keeps the temperature of the Sun constant, it has long been believed that the Sun is a continuously burning object. Refute this hypothesis based on the fact that the Sun is 73% hydrogen, 25% helium and other elements with a lower concentration. The specific heat of combustion of hydrogen is 141 MJ / kg. According to the hypothesis, it is assumed that the sun has access to an unlimited amount of oxygen for burning.
1) (calculation of the possible combustion energy)
Helium is an inert gas, therefore it cannot enter into a chemical combustion reaction with oxygen. This means that all the energy that will be released during the combustion of the volume of the substance that is part of the Sun can only be the energy of combustion of oxygen:
Q = qm = 0.73 * 1.989 * 10 ^ 30 * 141 * 10 ^ 6 = 204/7 * 10 ^ 36J.
2) (relationship with power and luminosity)
The luminosity of the Sun is equal to the power of its burning: P = L, and the power is the amount of energy during the time P = Q / t
3) (the hypothesis was correctly rejected, calculations were carried out and a conclusion was made (two points for each))
If we assume that the Sun’s matter would burn uniformly (that is, the luminosity would be constant), then the released energy would be enough for a time t = Q / P = 204.7 * 10 ^ 36 / (3.88 * 10 ^ 26) = 52.76 * 10 ^ 10 (c) or about 16,770 years, which is less than even the time of human existence. In addition, the Sun does not have such an amount of available oxygen. The hypothesis was rejected.
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