Unit 13 — Earth, the Solar System, and Space Science

Welcome back!

When you look into the night sky, you see only a tiny part of an enormous universe.

Our planet is one of many worlds that travel around the Sun.

Scientists use telescopes, satellites, spacecraft, and mathematics to study space and better understand our place in the cosmos.

Today you will explore Earth, the Solar System, and the universe beyond.

Earth in Space

Earth is a planet that orbits the Sun.

It has the conditions needed to support life, including:

• liquid water
• an atmosphere
• suitable temperatures
• energy from the Sun

Earth rotates on its axis once every 24 hours, producing day and night.

It revolves around the Sun once each year.

The Sun

The Sun is a star.

It is the center of our Solar System.

The Sun provides:

• light
• heat
• energy

Without the Sun, life on Earth would not exist.

Its gravity keeps the planets in orbit.

The Planets

Our Solar System contains eight major planets.

In order from the Sun:

• Mercury
• Venus
• Earth
• Mars
• Jupiter
• Saturn
• Uranus
• Neptune

The four inner planets are rocky.

The four outer planets are much larger and are made mostly of gases and ices.

Each planet has unique characteristics.

Moons, Asteroids, and Comets

Many planets have natural satellites called moons.

Other objects in the Solar System include:

• asteroids
• comets
• dwarf planets
• meteoroids

These objects help scientists learn about how the Solar System formed.

Gravity in the Solar System

Gravity keeps planets, moons, and other objects in motion.

Without gravity:

• planets would not orbit the Sun
• moons would not orbit planets
• galaxies would not stay together

Gravity acts across enormous distances.

Stars and Galaxies

The Sun is only one of billions of stars.

Most stars belong to enormous groups called galaxies.

Earth is located in the Milky Way Galaxy.

Beyond our galaxy are billions of other galaxies spread across the universe.

Space Exploration

People explore space using:

• telescopes
• satellites
• robotic spacecraft
• space probes
• space stations
• astronauts

Space exploration has increased our understanding of Earth and the universe.

Many technologies developed for space missions are now used in everyday life.

Protecting Earth

Studying space also teaches us about our own planet.

Scientists monitor:

• weather
• climate
• forests
• oceans
• natural disasters

Satellites help us better understand and protect Earth's environment.

Activity

Create a model of the Solar System.

Label:

• the Sun
• the eight planets
• Earth's Moon
• the asteroid belt

Then choose one planet and prepare a one-page report describing:

• size
• distance from the Sun
• atmosphere
• temperature
• moons
• one interesting fact

Practice

Answer these questions.

Why is the Sun important?

Name the eight planets in order from the Sun.

What causes day and night?

What is gravity?

What is a galaxy?

How do satellites help scientists?

Review

Today you learned:

• Earth is one planet in the Solar System
• the Sun provides light, heat, and energy
• gravity keeps planets and moons in orbit
• the Solar System contains many different objects
• our Solar System is part of the Milky Way Galaxy
• space exploration expands scientific knowledge
• satellites help us study and protect Earth

Studying space helps us better understand both the universe and our own planet.

Looking Ahead

Next we will explore ecosystems, biodiversity, and environmental stewardship, learning how living things interact and how people can help protect Earth's natural systems.