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Grolier Online
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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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    Text Set Grade 3: Solar System

    Text Set Grade 3: Solar System

    Text Sets build proficient readers of informational text as students read deeply and widely on an array of science and social studies topics. Teachers will love the 'hands on' material and feel confident about how to integrate the Common Core State Standards into their reading instruction.

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    Title list:
    • Classroom Books Library Bin—2 Bins
    • Do Stars Have Points?
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    • First Encyclopedia of Space
    • First Encyclopedia of Space (skills sheet)
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    • Planets
    • Planets (skills sheet)
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    • Text Set Implement Letter Gr 3 Solar System

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    Paperback Book Collection | Grade 3
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    Text Set Grade 3: Solar System
    Grade 3 $235.00
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    Scholastic Science Readers™ Level 3: Solar System

    Scholastic Science Readers™ Level 3: Solar System

    by Gregory L. Vogt

    Learn what the sun is made of, and how the sun's gravity makes the planets orbit around it. Find out how far each planet is from the sun, how many moons each planet has, and what the planets look like up-close!

    Why study the solar system? Space exploration could explain the history of the universe. It may also reveal whether there is other life out there!

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    Paperback Book | Grades 2-3
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