Solar System and the Universe

Solar System and the Universe

Middle School

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Learning Objectives

• Define the parts of our solar system and the role of gravity.

• Compare planets, dwarf planets, moons, and other objects in space.

• Describe the characteristics of the inner and outer planets.

• Explain the scientific theory of how the solar system formed.

• Understand the units used to measure large distances in space.

Key Vocabulary

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Solar System

The solar system includes the sun and all the objects that orbit it, like planets and moons.

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Astronomical Unit (AU)

An astronomical unit is the average distance from the center of the Earth to the sun's center.

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Planet

A planet is a large, round body that orbits the sun and has cleared its orbital path.

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Dwarf Planet

A dwarf planet is a spherical object that orbits the sun but has not cleared its path.

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Natural Satellite

A natural satellite is a celestial body, such as a moon, in orbit around a host planet.

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Asteroid

An asteroid is a small, primarily rocky body that is in orbit around the sun.

Key Vocabulary

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Meteoroid

Chunks of rock or dust that are smaller in size than an asteroid.

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Meteor

A streak of light that is created by a meteoroid due to air friction.

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Meteorite

A meteoroid that successfully passes through the atmosphere and strikes the surface of the Earth.

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Comet

A loose ball of ice and rock that has a very long and narrow orbit.

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What Makes Up Our Solar System?

• Our solar system has the sun, planets, their moons, and smaller objects.

• The sun’s gravity keeps all of these objects in their orbits.

• Gravitational pull depends on the mass of and distance between the objects.

• An astronomical unit (AU) measures the distance between the Earth and sun.

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Multiple Choice

What is responsible for keeping all the components of our solar system, including planets, moons, and smaller objects, in their orbits?

• The magnetic field of the planets

• The rotation of the Earth

• The sun's gravitational pull

• The light emitted by the sun

Multiple Choice

What does an astronomical unit (AU) measure?

• The distance between Earth and the Moon

• The distance between Earth and the Sun

• The diameter of Earth

• The size of the Solar System

Multiple Choice

Which of the following best describes a dwarf planet?

• A body that orbits a planet and is spherical

• A spherical object that orbits the Sun but has not cleared its orbit

• A rocky object that enters Earth’s atmosphere

• A planet that has no moons

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Inner and Outer Planet

Inner Planets

• ​The four inner planets are the planets located closest to the sun.

• ​​They are small and are made mostly of rock and metal.

• ​Earth is an example of a small, rocky inner planet.

Outer Planets

• ​The four outer planets are located much farther from the sun.

• ​​They are very large and are made mostly of gas and liquid.

• ​Jupiter is an example of a large, gaseous outer planet.

Multiple Choice

Which characteristic is primarily used to classify planets as either inner or outer planets?

• Their size and mass

• The color they appear in the sky

• Their location relative to the sun

• The number of moons they have

Multiple Choice

How do the general characteristics of inner planets compare to those of outer planets?

• Inner planets are small and gaseous, while outer planets are large and rocky.

• Inner planets are large and gaseous, while outer planets are small and rocky.

• Inner planets are small and rocky, while outer planets are large and gaseous.

• Both groups of planets are small and rocky.

Multiple Choice

A scientist discovers a new planet that is very large and composed mostly of gas and liquid. Where is this planet most likely located?

• Between the inner and outer planets

• Far from the sun, with the other outer planets

• Close to the sun, with the other inner planets

• In the same orbit as Earth

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Dwarf Planets and Moons

Dwarf Planets

• A dwarf planet is an object that orbits the sun and is massive enough to be spherical.

• It has not cleared the area of its orbit of other smaller objects and debris.

• The five known dwarf planets are Pluto, Eris, Ceres, Makemake, and Haumea.

Moons

• A moon, or natural satellite, is a celestial body that orbits a host planet.

• The gravitational pull between the planet and its moon keeps the moon in orbit.

• Among the eight planets, only Mercury and Venus do not have any moons.

Multiple Choice

Which statement best describes a dwarf planet?

• It is one of the eight major planets in our solar system.

• It is kept in orbit by the gravitational pull of a larger planet.

• It is an object that orbits the sun and has not cleared its orbital area.

• It is a celestial body that orbits a host planet.

Multiple Choice

What is the primary reason a moon orbits a planet?

• The moon is always spherical, just like a planet.

• The planet's gravitational pull keeps the moon in orbit.

• The moon has not cleared its orbit of other objects.

• The moon is smaller than the planet it orbits.

Multiple Choice

An astronomer discovers a new, spherical celestial body. It orbits the sun, but it shares its orbital path with many other small objects. How would this body most likely be classified?

• As a planet, because it is spherical and orbits the sun.

• As a moon, because it orbits the sun just like a planet's moon.

• As a dwarf planet, because it has not cleared its orbital area.

• As a moon, because it is near other objects.

Smaller Solar System Objects

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Asteroids

• ​Asteroids are small, rocky bodies that are found orbiting the sun.

• ​​Many of them are located in the asteroid belt.

• ​This area exists between the orbits of Mars and Jupiter.

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Meteoroids and Meteors

• ​Meteoroids are small chunks of rock or dust in space.

• ​​A meteor is the streak of light they make in our atmosphere.

• ​When it hits the ground, it is called a meteorite.

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Comets

• ​Comets are large balls made of ice, rock, and dust.

• ​​They travel around the sun in very long, narrow orbits.

• ​As comets get closer to the sun, they develop tails.

Multiple Choice

What is a key characteristic of asteroids?

• They are streaks of light that appear in Earth's atmosphere.

• They are small, rocky bodies primarily found in a belt between Mars and Jupiter.

• They are chunks of dust that are only found far away from the sun.

• They are large balls of ice that develop tails near the sun.

Multiple Choice

How does the composition of a comet differ from that of an asteroid?

• Comets are made of ice, while asteroids are made of dust.

• Comets are made of rock and metal, while asteroids are made of gas.

• Comets and asteroids are both made primarily of rock.

• Comets are made of ice, rock, and dust, while asteroids are primarily rocky.

Multiple Choice

A small, rocky object is traveling through space before it enters Earth's atmosphere and burns up, creating a bright streak of light. Which terms correctly describe the object's journey?

• It was a meteoroid in space, and it became a meteor in the atmosphere.

• It was a comet in space, and it became a meteor in the atmosphere.

• It was a meteorite in space, and it became a meteor in the atmosphere.

• It was a meteor in space, and it became a meteoroid in the atmosphere.

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How the Solar System Formed

• The solar system formed 4.6 billion years ago from a huge gas cloud.

• Gravity pulled this cloud into a dense, hot, and spinning disk.

• The hot center created our sun through a process called nuclear fusion.

• Rock, ice, and gas in the disk formed the planets and moons.

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Multiple Choice

What did the solar system form from about 4.6 billion years ago?

• A massive cloud of gas

• A single, large planet

• The explosion of a star

• A collection of asteroids and comets

Multiple Choice

What caused the original gas cloud to form into a dense, hot, and spinning disk?

• The force of gravity pulling it together

• The cloud's own rapid spinning motion

• A large explosion from within the cloud

• The heat from a nearby star

Multiple Choice

Which statement best explains why the sun is at the center of the solar system?

• The planets formed first and were then drawn towards the largest one, which became the sun.

• The sun was a pre-existing star that captured the planets with its gravity.

• The center of the spinning gas disk became the hottest and densest part, forming the sun through nuclear fusion.

• The rock and ice in the gas cloud were heavier, so they all collected in the middle to form the sun.

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Common Misconceptions

Misconception	Correction
The sun is a solid ball of fire.	The sun is a star of hot gas that makes energy through nuclear fusion.
All planets are solid and rocky like Earth.	The outer planets are large and made mostly of gas and liquid.
‘Shooting stars’ are actually stars.	They are streaks of light from small rocks burning up in our atmosphere.
Pluto was ‘demoted’ because it is too small.	Pluto is a dwarf planet because it has not cleared its orbital path.

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Summary

• Our solar system is a gravity-bound system with the sun at its center.

• It formed about 4.6 billion years ago from a giant cloud of gas and dust.

• Planets are either inner, rocky worlds or outer, gas-and-liquid giants.

• Other objects include dwarf planets, asteroids, comets, and meteoroids.

Poll

On a scale of 1-4, how confident are you about the concepts covered in today's review?

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