Facts About the Sun's Core
The sun's core, the innermost layer of the sun, is plasma, a type of gas that is sensitive to magnetism. The sun's energy is derived from its core. Fusion reactions that occur in the core release extreme amounts of heat and energy in the form of gamma rays and neutrinos.
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Properties
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The temperature in the core of the sun is 15 million Kelvin. It has a density of 150 g/cubic cm, which is 15 times that of lead (See Reference 1). However, even though the core of the sun is extremely dense, it remains plasma because of its extreme heat. The core's high temperature and density is because of a fusion reaction and the extreme pressure that exists in the core. Half of the sun's mass exists in the core while only containing about 2 percent of the sun's volume (See Reference 1).
Composition
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The initial composition of the sun by mass was 72 percent hydrogen, 26 percent helium and 2 percent heavier elements (See Reference 1). The fusion reaction that occurs in the core has changed its chemical composition. Today there is about 35 percent hydrogen by mass in the center of the core and 65 percent hydrogen by mass at the edge of the core (See Reference 1).
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Reaction
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A nuclear fusion reaction occurs in the sun's core. Through a series of reactions, hydrogen atoms containing a single proton are forced together. In normal situations, the protons would repel each other, but the high temperature and density of the core force the hydrogen nuclei together (See Reference 3). In a proton-proton chain reaction, two hydrogen atoms fuse together and immediately decay to form a positron, a neutrino and deuterium (a isotope of hydrogen with a mass of 2). Another hydrogen atom fuses with the deuterium, forming helium-3 and a gamma ray. Then, two helium-3 isotopes fuse to form helium-4 and two protons. In other words, in this reaction hydrogen fuses to become helium, releasing gamma rays, neutrinos and protons during the reactions. (See Resource 1).
Gamma Rays
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Gamma rays particles of light with extremely high energy and frequency. These gamma rays are emitted and reabsorbed in a series of reactions that occur in the sun's core. When they are released from the atoms, their energy is reduced. However, because energy cannot be created nor destroyed, when the energy of the gamma rays is reduced, the overall number of photons increases, thus, creating the same overall energy in the sun (See Reference 2).
Neutrinos
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Neutrinos are neutral particles that are released by the sun's core in a fusion reaction. They are non-reactive particles. Neutrino detectors have been built that use the isotope chlorine-37. When neutrinos pass through chlorine-37, it becomes argon-37. The ration of argon-37 to chlorine-37 can indicate how many neutrinos have passed through the detector (See Reference 2). Neutrinos have become a source of study and contention among scientists. It is estimated that the sun produces three times more neutrinos than are detected. Therefore, neutrinos are the focus of the dark-matter controversy that exists among physicists (See Resource 2).
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