Grolier Online
Discover the content connection—the definitive, fully integrated database collection and online research portal. It includes seven encyclopedia databases: Encyclopedia America, Grolier Multimedia Encyclopedia, The New Book of Knowledge, La Nueva Enciclopedia Cumbre, America the Beautiful, Lands and Peoples, and The New Book of Popular Science.

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.

  • Teacher Store
  • The Teacher Store  
    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.

    Each grade–level selection offers four individual subject packs, available separately. Each subject pack* includes 55 trade paperbacks and helps teachers integrate the CCSS into reading instruction through:
    • Read Aloud (1 title, 1 copy)
    • Anchor Text (1 title, 30 copies)
    • Supporting Texts (4 titles, 6 copies each)
    • 4 text–based skill–building sheets for students (1 per supporting text and each noted with the specific CCSS ELA standard addressed)
    • Teacher Implementation Letter with Essential Question Prompts, Suggested Writing Topics and more
    • Book bin

    Text Sets are essential for every K–6 classroom, and align with the CCSS by:
    Engaging the whole class on a single topic
    • Modeling a
    close reading of a text
    • Deepening subject knowledge by
    reading across multiple texts
    • Providing opportunities for text–dependent responses from students

    Text Sets optimize every classroom reading opportunity, and its flexible configuration is ideal for whole class teaching, small group instruction, and independent reading.

    Order all four subject packs in each grade for a total of 220 books per grade level.

    *(The Kindergarten pack includes math too.)

    See below for complete list of titles. Appropriate titles of equal value may be substituted if any of the listed titles are unavailable at shipping time.

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

    $235.00 You save: 51%
    Paperback Book Collection | Grade 3
    Add To Cart
    Educators Only
    Text Set Grade 3: Solar System
    Grade 3 $235.00
    Add To Cart
  • Teacher Store
  • The Teacher Store  
    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!

    Features full-color, up-close photographs of the planets in the Earth's solar system.

    A simple explanation of the sun, moon, and the nine planets, with additional facts about asteroids and space exploration.

    $5.95 You save: 25%
    Paperback Book | Grades 2-3
    Add To Cart
    Educators Only