Do you agree or disagree? 1. Seasons are caused by the changing distance between Earth and the Sun. 2. The Moon has a dark side upon which the Sun never shines. 3. The solar system contains nine planets. 4. Earth is the only planet that has a moon. Chapter Introduction

Do you agree or disagree? 5. The Sun is more massive than 90 percent of other stars. 6. The solar system is at the center of the Milky Way. Chapter Introduction

Lesson 1 Reading Guide - Vocab The Sun-Earth-Moon System revolution rotation equinox solstice waxing waning tide eclipse Lesson 1 Reading Guide - Vocab

Earth and the Universe Earth is one of eight planets that orbit the Sun. The Sun is one of billions of stars that make up the Milky Way galaxy. The Milky Way is one of billions of galaxies in the universe. Lesson 1-1

The Sun is 100 times wider than Earth and 10 times wider than the planet Jupiter. The Sun and Jupiter are the two largest objects in the solar system. Lesson 1-1

Motions of Earth (cont.) The orbit of an object around another object is revolution. Jason Reed/Getty Images Lesson 1-2

Motions of Earth (cont.) Rotation is the spin of an object around its axis. Earth spins, or rotates, on its axis like a top. Lesson 1-2

Motions of Earth (cont.) Earth’s rotation causes day and night. Lesson 1-2

Earth’s Tilt and Seasons Seasons occur because Earth’s tilt does not change as Earth orbits the Sun. Lesson 1-3

When the North Pole is toward the Sun, it is summer in the northern hemisphere. When the South Pole is toward the Sun, it is winter in the northern hemisphere. Lesson 1-3

Earth’s Moon (cont.) The Moon is visible because it reflects sunlight. The Moon completes a cycle of phases every 29.5 days. Lesson 1-4

Tides Tides are the periodic rise and fall of the oceans’ surfaces caused by the gravitational force between Earth and the Moon and the Sun. The Moon has more influence on tides than the Sun because it is closer to Earth than the Sun. Lesson 1-5

Tides (cont.) High tides on Earth occur at locations closest to and farthest from the Moon. Most coastlines have two high tides and two low tides each day. Lesson 1-5

During a solar eclipse, a small part of Earth is in the Moon’s shadow. The Moon appears to completely or partially cover the Sun. Lesson 1-6

During a lunar eclipse, Earth’s shadow completely or partially covers the Moon. The Moon is visible during a total lunar eclipse because light changes direction as it passes through Earth’s atmosphere. Lesson 1-6

How long does it take Earth to revolve once around the Sun? A. 5 years B. 6 months C. 24 hours D. 365.25 days Lesson 1 – LR2

A lunar eclipse occurs during which type of moon? A. full moon B. new moon C. waning moon D. waxing moon Lesson 1 – LR3

Lesson 2 Reading Guide - Vocab The Solar System planet dwarf planet moon asteroid comet meteoroid meteor Lesson 2 Reading Guide - Vocab

Lesson 2-3

Lesson 2-3

The Solar System (cont.) What objects are in the solar system? Lesson 2-4

The cores of the inner planets are mostly iron. The four inner planets formed from rocks and heavy elements left behind from the creation of the solar system. The cores of the inner planets are mostly iron. Mercury: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington; Venus: NASA; Earth: NASA Goddard Space Flight Center; Mars: NASA/JPL/Malin Space Science Systems Lesson 2-4

The inner planets are the smallest planets. They have few or no moons, no rings, and they rotate more slowly than the outer planets. Mercury: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington; Venus: NASA; Earth: NASA Goddard Space Flight Center; Mars: NASA/JPL/Malin Space Science Systems Lesson 2-4

The four outermost planets formed farther from the Sun than the inner planets did. They have more gases and other materials with low boiling points and are often called the gas giants. Earth: NASA Goddard Space Flight Center; Jupiter: NASA/JPL/USGS; Saturn: NASA and The Hubble Heritage Team (STScI/AURA)Acknowledgment: R.G. French (Wellesley College), J. Cuzzi (NASA/Ames), L. Dones (SwRI), and J.; Uranus, Neptune: NASA/JPL Lesson 2-5

They are larger than the inner planets, they rotate more quickly, and they each have rings. These planets do not have solid surfaces. They have thick atmospheres of hydrogen and helium. Earth: NASA Goddard Space Flight Center; Jupiter: NASA/JPL/USGS; Saturn: NASA and The Hubble Heritage Team (STScI/AURA)Acknowledgment: R.G. French (Wellesley College), J. Cuzzi (NASA/Ames), L. Dones (SwRI), and J.; Uranus, Neptune: NASA/JPL Lesson 2-5

The Solar System (cont.) How do the inner and outer planets differ? Lesson 2-5

Lesson 3 Reading Guide - Vocab Stars, Galaxies, and the Universe star light-year galaxy Big Bang theory Lesson 3 Reading Guide - Vocab

Stars A star is a large sphere of hydrogen gas hot enough for nuclear reactions to occur in its core. Lesson 3-1

Stars (cont.) When measuring distances to stars, astronomers use a unit of distance based on the speed of light. A light-year is the distance light travels in one year. Light travels 300,000 km/s. One light-year equals 9.46 trillion km. Lesson 3-1

Stars (cont.) The color of a star indicates its temperature. Lesson 3-1

Stars (cont.) Blue stars are the hottest stars, followed by blue-white, white, yellow, orange, and red stars. The Sun is a yellow star. Lesson 3-1

Stars (cont.) The Sun is larger and more massive than 90 percent of other stars but is still tiny compared to the some giant stars. Lesson 3-1

Stars (cont.) The Sun will continue to shine for another 5 billion years. Then it will became a small, dense, white dwarf star. SOHO (ESA & NASA) Lesson 3-1

Stars (cont.) How does the Sun compare in size to other stars? Lesson 3-1

Stars (cont.) In a binary star system, two stars orbit each other’s center of mass. In a multiple-star system, two or more stars orbit the entire system’s center of mass. Lesson 3-1

Galaxies A galaxy is a huge collection of stars, gas, and dust. Astronomers classify galaxies by their shapes. JPL/NASA Local Group Galaxies Survey Team, NOAO, AURA, NSF NASA/JPL-Caltech/S. Willner (Harvard-Smithsonian Center for Astrophysics) Elliptical galaxy Irregular galaxy Spiral galaxy Lesson 3-2

The Universe Most galaxies are pulled by gravity into clusters of galaxies. The Milky Way is part of a cluster called the Local Group, which contains about 30 galaxies. Superclusters are some of the largest structures in the universe and may contain thousands of galaxies. Lesson 3-3

The Universe (cont.) How is the universe structured? Lesson 3-3

The Universe (cont.) The Big Bang theory states that the universe began from one point and has been expanding and cooling ever since. Photodisc/Getty Images Lesson 3-3

Which is the distance light travels in one year? A. astronomical unit B. galaxy C. light year D. supercluster Lesson 3 – LR1

Astronomers classify galaxies by which of these? A. color B. density C. shape D. size Lesson 3 – LR2

Which type of star system has two or more stars that orbit the entire system’s center of mass? A. binary B. elliptical C. irregular D. multiple Lesson 3 – LR3

5. The Sun is more massive than 90 percent of other stars. Do you agree or disagree? 5. The Sun is more massive than 90 percent of other stars. 6. The solar system is at the center of the Milky Way. Lesson 3 - Now

How long does it take the Earth to make one full rotation? A. 24 hours B. 6 months C. 365.25 days D. 5 years Chapter Review – MC2

Which term describes small, rocky objects that orbit the Sun? A. moons B. dwarf planets C. comets D. asteroids Chapter Review – MC3

When a meteoroid impacts the Earth, what does it become? A. meteorite B. meteor C. comet D. asteroid Chapter Review – MC4

Which term refers to a huge collection of stars, gas, and dust? A. galaxy B. light year C. solar system D. universe Chapter Review – MC5

Which describes the spin of an object around its axis? A. orbit B. revolution C. rotation D. solstice Chapter Review – STP1

Which occurs when Earth’s rotation axis is tilted neither toward nor away from the Sun? A. eclipse B. equinox C. solstice D. tides Chapter Review – STP2

Which is a natural satellite that orbits an object other than a star? A. dwarf planet B. meteoroid C. moon D. planet Chapter Review – STP3

Which describes the streak of light produced when a meteoroid enters Earth’s atmosphere? A. asteroid B. comet C. meteor D. meteorite Chapter Review – STP4

Which is a large sphere of hydrogen gas hot enough for nuclear reactions to occur in its core? A. star B. planet C. light-year D. galaxy Chapter Review – STP5