The Physics
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Temperature at the Center of the Sun

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Pasachoff, Jay M. Peterson-First Guides to Astronomy. Boston: Houghton Mifflin, 1988. "It is about 15,000 °C (27,000 °F) at its center" 15,000 K
New Book of Knowledge. New York: Grolier, 1996: Vol. 17S. "so that at the center of the sun we should find a very hot core with a temperature that reaches about 27,000,000 °F (15,000,000 °C)" 15,000,000 K
Microsoft Encarta '95. Redmond, WA: Microsoft, 1995. "The approximate temperature at the center of the sun is 16,000,000 K (29,000,000 °F)" 16,000,000 K
Sagan, Carl. Cosmos. New York: Random House, 1980. "The temperature at the core is an incredible 59 million °F (15 million K)" 15,000,000 K
Concise Columbia Electronic Encyclopedia. New York: Columbia University, 1994. "The temperature of the core is an incredible 20 million degrees centigrade" 20,000,000 K

The determination of the sun's temperature has been one of the most difficult problems in solar astronomy. An English astronomer, Sir John Hershel at the Cape of Good Hope, and Claude-Servais-Mathias Pouillet in France (1837), observed that if the vertical rays of the sun were totally absorbed, would raise the temperature of a layer of water 1.8 cm deep by 1 °C/minute. The measurement is easy, but the atmospheric absorption has been the uncertain factor. The problem was solved in 1881 and again in 1904, when astronomers gathered the unknown data for the solar radiation of different wavelengths from data already known, in order to determine what the intensity of each would be if there were no intervening air.

The temperature at the center (core) of the Sun is about 15,000,000 K. The tremendous pressures on the densely packed atoms of helium and hydrogen within the sun are what causes the sun's interior to be extremely hot. If the sun had more mass, there would be greater pressure, therefore the temperature would be much higher because the nuclear-fusion of hydrogen and helium can only occur at extremely high temperatures. Different calculations give results from 13,000,000 K to 25,000,000 K. Not all scientists agree about the temperature within the sun's interior because they have different calculations of the mass of the sun and that is how they determine the pressure inside the core. The Sun emits energy over all wavelengths, from x-rays to radio waves. Approximately 40% of the emitted energy is in the visible portion of the spectrum, 50% is in the infrared, and the remainder is in the ultraviolet.

Dedra Forbes -- 1997