noun, the star at the centre of our solar system. It is a gaseous body having a highly compressed core, in which energy is generated by thermonuclear reactions (at about 15 million kelvins), surrounded by less dense radiative and convective zones serving to transport the energy to the surface (the photosphere). The atmospheric layers (the chromosphere and corona) are normally invisible except during a total eclipse. Mass and diameter: 333 000 and 109 times that of earth respectively; mean distance from earth: 149.6 million km (1 astronomical unit). Related adj solar

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©HarperCollins 2008. Collins English Dictionary definition of sun