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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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    Moon, The

    Moon, The

    by Christine Taylor-Butler

    Human beings first set foot on the Moon on July 20, 1969, marking one of the most important events in the history of space exploration. Since then, scientists have continued to learn more about Earth’s sole natural satellite. Readers will learn what it is like to walk on the surface of the Moon and what role the satellite plays in the solar system. They will also find out how scientists first began studying the Moon and how they are continuing their exploration today.

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    Earth

    Earth

    by Elaine Landau

    SET FEATURES:

    •     Superb age-appropriate introduction to curriculum-relevant subjects
    •     Covers all studies, from Animals to American History, Geography to Science
    •     "Words to Know" glossary clarifies subject-specific vocabulary
    •     "Learning More" section encourages independent study
    •     Index makes navigating subject matter easy

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      11/1/07 School Library Journal
      Featuring a new author and a colorful redesign, these volumes expertly update Larry Dane Brimner's 1998 editions, and also add a title that looks past Pluto into the Kuiper Belt, the Oort Cloud, and the search for extrasolar planets. Each one matches a clearly reasoned, matter-of-fact text to plenty of small but sharply reproduced color photos and pages of new or restated facts, and rounded off with multimedia lists of audience-appropriate further resources. Despite minor bobbles (for instance, Landau assigns the space probe New Horizons different speeds in Pluto and Beyond Pluto), these remain the gold standard for post-picture-book nonfiction, and should be first purchases for any library that serves fledgling readers.

       

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