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The core of the Sun is considered to extend from the center to about 0.2 solar radius. It is the hottest part of the Solar System. It has a density of up to 150,000 kg/m3 (150 times the density of water on Earth) and a temperature of close to 15,000,000 Kelvins (by contrast, the surface of the Sun is close to 6,000 Kelvins). Energy is produced by exothermic thermonuclear reactions (nuclear fusion) that mainly convert hydrogen into helium. The core is the only location in the Sun that produces an appreciable amount of heat via fusion: the rest of the star is heated by energy that is transferred outward from the core. All of the energy produced by fusion in the core must travel through many successive layers to the solar photosphere before it escapes into space as sunlight or kinetic energy of particles. Image File history File links SunLayers. ...
Image File history File links SunLayers. ...
“Sol†redirects here. ...
“Sol†redirects here. ...
In astronomy, the solar radius is a unit of length used to express the size of stars and larger objects such as galaxies. ...
Major features of the Solar System (not to scale; from left to right): Pluto, Neptune, Uranus, Saturn, Jupiter, the asteroid belt, the Sun, Mercury, Venus, Earth and its Moon, and Mars. ...
Impact from a water drop causes an upward rebound jet surrounded by circular capillary waves. ...
In thermodynamics, the word exothermic describes a process or reaction that releases energy in the form of heat. ...
In physics, nuclear fusion (a thermonuclear reaction) is a process in which two nuclei join, forming a larger nucleus and releasing energy. ...
The deuterium-tritium (D-T) fusion reaction is considered the most promising for producing fusion power. ...
General Name, Symbol, Number hydrogen, H, 1 Chemical series nonmetals Group, Period, Block 1, 1, s Appearance colorless Atomic mass 1. ...
General Name, Symbol, Number helium, He, 2 Chemical series noble gases Group, Period, Block 18, 1, s Appearance colorless Standard atomic weight 4. ...
For other uses, see Heat (disambiguation) In physics, heat, symbolized by Q, is energy transferred from one body or system to another as a result of a difference in temperature. ...
Prism splitting light High Resolution Solar Spectrum Sunlight in the broad sense is the total spectrum of the electromagnetic radiation given off by the Sun. ...
The kinetic energy of an object is the extra energy which it possesses due to its motion. ...
About 3.6 ×1038 protons (hydrogen nuclei) are converted into helium nuclei every second, releasing energy at the matter-energy conversion rate of 4.3 million tonnes per second, 380 yottawatts (3.8 ×1026 W) or 9.1 ×1010 megatons of TNT per second. The rate of nuclear fusion depends strongly on density, so the fusion rate in the core is in a self-correcting equilibrium: a slightly higher rate of fusion would cause the core to heat up more and expand slightly against the weight of the outer layers, reducing the fusion rate and correcting the perturbation; and a slightly lower rate would cause the core to cool and shrink slightly, increasing the fusion rate and again reverting it to its present level. In physics, the proton (Greek proton = first) is a subatomic particle with an electric charge of one positive fundamental unit (1. ...
The watt (symbol: W) is the SI derived unit of power, equal to one joule per second. ...
A megaton or megatonne is a unit of mass equal to 1,000,000 metric tons, i. ...
R-phrases S-phrases Related Compounds Related compounds picric acid hexanitrobenzene Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa) Infobox disclaimer and references Trinitrotoluene (TNT) is a chemical compound with the formula C6H2(NO2)3CH3. ...
In physics, thermal expansion is the tendency of matter to increase in volume or pressure when heated. ...
A spring scale measures the weight of an object In the physical sciences, weight is a measurement of the gravitational force acting on an object. ...
Look up perturbation in Wiktionary, the free dictionary. ...
The high-energy photons (gamma and X-rays) released in fusion reactions take a long time to reach the Sun's surface, slowed down by the indirect path taken, as well as by constant absorption and reemission at lower energies in the solar mantle. Estimates of the "photon travel time" range from as much as 50 million years[1] to as little as 17,000 years.[2] After a final trip through the convective outer layer to the transparent "surface" of the photosphere, the photons escape as visible light. Each gamma ray in the Sun's core is converted into several million visible light photons before escaping into space. Neutrinos are also released by the fusion reactions in the core, but unlike photons they very rarely interact with matter, so almost all are able to escape the Sun immediately. For many years measurements of the number of neutrinos produced in the Sun were much lower than theories predicted, a problem which was recently resolved through a better understanding of the effects of neutrino oscillation. In modern physics the photon is the elementary particle responsible for electromagnetic phenomena. ...
The optical spectrum (light or visible spectrum) is the portion of the electromagnetic spectrum that is visible to the human eye. ...
Neutrinos are elementary particles denoted by the symbol ν. Travelling close to the speed of light, lacking electric charge and able to pass through ordinary matter almost undisturbed, they are extremely difficult to detect. ...
The solar neutrino problem was a major discrepancy between measurements of the neutrinos flowing through the Earth and theoretical models of the solar interior, lasting from the mid-1960s to about 2002. ...
Neutrino oscillation is a quantum mechanical phenomenon predicted by Bruno Pontecorvo whereby a neutrino created with a specific lepton flavor (electron, muon or tau) can later be measured to have a different flavor. ...
Fusion in the Solar Core The most important fusion process in nature is that which powers the stars. The net result is the fusion of four protons into one alpha particle, with the release of two positrons, two neutrinos, and energy. For stars the size of the sun, the proton-proton chain dominates. Image File history File links FusionintheSun. ...
Image File history File links FusionintheSun. ...
The proton-proton chain reaction is one of two fusion reactions by which stars convert hydrogen to helium, the other being the CNO cycle. ...
An alpha particle is deflected by a magnetic field Alpha radiation consists of helium-4 nuclei and is readily stopped by a sheet of paper. ...
At the temperatures and densities in the solar core the rates of fusion reactions are extremely slow. For example, at solar core temperature (T ~ 15 MK) and density (~150 g/cm3), the energy release rate is only ~11 W/m3 for the core (~0.25 W/m3 for the sun) - millions of times less than the rate of energy release of ordinary candles and hundreds of times less than the rate at which a human body generates heat. Thus, reproduction of stellar core conditions in a lab for nuclear fusion power production is completely impractical.
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