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Structure of the Sun: Inner Core

Structure of the Sun
From its innermost core to its corona and to the solar wind that extends far past the Earth, the Sun has a structure typical of most stars of its kind.

Inner Core. The weight of the Sun's outer layers compresses the gas of the innermost region to a density about 100 times that of water and raises the central temperature to about 15 million K (27,000,000° F). Throughout the Sun's interior, atoms collide frequently and with enough energy to ionize the gas, which is then referred to as a plasma. In the inner third of the Sun the collisions among ions are energetic enough to cause nuclear reactions at a rate sufficient to liberate the energy required to give the Sun's observed luminosity. The specific set of reactions thought to be most effective in generating energy in the Sun involves the burning of hydrogen to helium, following the specific sequence of reactions known as the proton-proton reaction. Present evidence suggests that the plasma of the central nuclear burning region of the Sun is not mixed with the material in the outer shells. Thus the proton-proton reaction will continue only until the hydrogen of the central region, some 10% of the Sun's mass, becomes transformed into helium after about 10 billion years. The Sun's age is estimated to be about 5 billion years. The gamma rays and X rays emitted by the nuclear reactions travel outward with little absorption through the solar interior, because the electrons that allow an atom to absorb light have mostly been stripped from the nuclei by interatomic collisions.

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    Pluto: Dwarf Planet

    Pluto: Dwarf Planet

    by Christine Taylor-Butler

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    11/1/07 School Library Journal
    These titles, which were originally published in 2005, all feature an updated boilerplate map of the planets (except in Mars, where Pluto's orbit is still visible) but only Pluto has undergone enough other revision to consider as a replacement. For libraries that don't own them already, however, they make appealing choices for their colorful layouts, simple writing, and emergent-reader-friendly facts.

     

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    First Encyclopedia of Science

    First Encyclopedia of Science

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    Breathtaking photographs and informative digital illustrations reveal the surprising science behind events in the everyday world. From the deep mysteries of the atom to the futuristic marvels of technology, enthusiastic young readers will learn about the breadth of the subject

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