Why does the sun shine?

The sun glows and heats up in the central area through the reaction of hydrogen fusion into helium.

This is a nuclear fusion reaction on the sun.

The surface temperature of the sun is about 6000 degrees, but inside it, the temperature is as high as150000 degrees. At this temperature, four hydrogen nuclei can be fused into 1 helium nuclei. In this process, 0.7% of matter is converted into energy.

According to Einstein's mass-energy formula E = MC 2, every "burning" 1 kg of hydrogen can release 6.4×10/4 joules of energy, which is equivalent to the energy generated by burning 19000 tons of coal. According to the current total radiation of the sun, more than 600 million tons of hydrogen is converted into helium every second. This sounds a lot, but it is actually only a small part of the mass of the sun. If the mass of the sun is an integer, it is about 2×10 33g, or 2×10 27g. The sun converts 6× 10 8 tons of hydrogen into helium every second, and "burns" less than 2×10/6 tons of fuel every year. According to this consumption rate, only 2× 10.26 tons of hydrogen is used in10 billion years, accounting for only 10% of the total mass of the sun. In the long period of 5 billion years, the sun consumed less than 5% of its mass. According to the current nuclear fusion reaction rate of the sun, the sun can "burn" stably for 3.32× 10/7 seconds, which is about 10 10 years, that is,10 billion years, so the sun has just reached middle age. It can also "burn" stably for more than 5 billion years.