Nature of the Sun

The sun is a star. It is often called an "average" star, though stars vary so much in size, energy output, and other characteristics that to call any star average is in a sense misleading. But the Sun is indeed roughly intermediate among the various classes of stars. The most luminous known stars are roughly a million times brighter than the Sun, while the least luminous known stars are three hundred thousand times less bright than the Sun. "Supergiant" stars are a hundred to a thousand times larger in diameter than the Sun. "Main Sequence" stars (most of them) are from ten times to one tenth the Sun's size. "White dwarf" stars are a hundred times smaller than the Sun (about the size of the Earth), while "neutron stars" are only a few miles across (Noyes 7-11).

The basic characteristic of stars is that they shine. Starlight comes from heat, which in turn is produced in one of three basic ways. Early and late in life, stars shine from heat generated by their own gravitational compression. White dwarfs stars at the end of life -- shine

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t in the form of infrared radiation. In the early stages of collapse the infrared escaped freely, but as the dust grew denser it was trapped, and the material of the solar nebula, previously cold, began to heat up. About half a million years had passed since the beginning of the collapse. At this time, the solar nebula made the gradual transition into a protostar. The temperature increased most rapidly towards the center of the solar nebula-protostar, reaching thousands and eventually millions of degrees (Ibid. 232). Part of the resulting heat escaped from the solar protostar, and it became identifiable from a distance as an infrared star. Cold opaque dust in the outer portion of the nebula still made it undetectable at the wavelengths of visible light. Eventually this dark outer cloak was driven away by the solar wind, and the Sun became a visible star. A belt of outlying matter survived in a ring around the proto-Sun's equator to form the planets and other bodies of the Solar System -- including, ultimately, ourselves. The Sun finally became visible to human-like eyes, to whom it would have appeared as an irregular red variable. It was for a while several hundred times brighter than the Sun we know today, shining fro
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Approximate Word count = 1765
Approximate Pages = 7 (250 words per page)

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