The Solar System

The Solar System

Middle School

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Learning Objectives

• Define the key components of the solar system, like the Sun, planets, and moons.

• Compare and contrast the characteristics of the inner and the outer planets.

• Explain the classification of asteroids, comets, and meteoroids.

• Describe the heliocentric model and the official definition of a planet.

Key Vocabulary

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Star

An extremely hot, dense mass of gases that gives off light as the gases burn.

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Planet

A celestial body that orbits the Sun, is nearly spherical, and has cleared its orbital path.

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Moon

A celestial body held in orbit by the gravitational pull of the planet it orbits.

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Asteroid

A small, rocky object that orbits the Sun, mostly located in the asteroid belt.

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Meteoroid

A rocky object that is smaller than an asteroid and moves between the planets in space.

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Comet

A small mass of dust and ice that has a long, elliptical orbit around the Sun.

Key Vocabulary

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Heliocentric Model

The model of the solar system that places the Sun in the center with planets revolving around it.

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Axis

An imaginary line running through the center of a sphere on which the sphere rotates.

The Sun and Solar System

• The Sun is the most massive object in our solar system.

• Its gravitational pull keeps planets and other objects in orbit.

• The Sun is at the center of the heliocentric solar system.

Multiple Choice

Which statement accurately describes the arrangement of the heliocentric solar system?

• The Sun is at the center, and planets orbit it.

• The Earth is at the center, and the Sun orbits it.

• The planets are all lined up in a straight line from the Sun.

• The Sun and planets all float randomly without a central point.

Multiple Choice

What is the relationship between the Sun and the planets' orbits?

• The Sun's gravitational pull keeps them in their paths.

• The Sun's light pushes the planets forward in a circle.

• The planets are all connected to the Sun by invisible strings.

• The planets move in straight lines until they hit something.

Multiple Choice

Based on the information, what is the most likely consequence if the Sun were a much less massive star?

• The Sun's gravitational pull would be weaker, and planets might not stay in orbit.

• The Sun's gravitational pull would become stronger, pulling planets closer.

• The planets' orbits would remain unchanged regardless of the Sun's mass.

• The Sun would get brighter, but the planets' orbits would be the same.

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Inner vs. Outer Planets

Inner Planets

• ​The four planets closest to the Sun are known as the inner planets.

• ​​They are smaller, mostly solid, and made of rock and minerals.

• ​These planets have much higher average temperatures due to their proximity to the Sun.

Outer Planets

• ​The four planets farthest from the Sun are known as the outer planets.

• ​​They are much larger than the inner planets and are composed mostly of gas.

• ​The outer planets are significantly colder due to their distance from the Sun.

Multiple Choice

What are the main characteristics used to classify planets as either inner or outer planets?

• Their distance from the Sun and what they are made of.

• The number of moons each planet has.

• The speed at which the planets spin.

• The color and brightness of the planets.

Multiple Choice

What is the primary reason for the major temperature differences between the inner and outer planets?

• The speed of their orbit.

• Their distance from the Sun.

• The presence of rings.

• Their size and mass.

Multiple Choice

Imagine a new planet is discovered that is much larger than Earth and is located very far from the Sun. Based on these characteristics, what can you conclude about this planet?

• It is likely a hot planet made mostly of rock.

• It is likely a cold planet made mostly of rock.

• It is likely a hot planet made mostly of gas.

• It is likely a cold planet made mostly of gas.

Defining Planets, Dwarf Planets, and Moons

• A planet orbits the sun and has cleared its path of smaller objects.

• A dwarf planet has not cleared its orbit of other smaller celestial objects.

• A moon is a celestial object that orbits a planet.

Multiple Choice

What is the key difference used to distinguish a planet from a dwarf planet?

• A planet is much larger than a dwarf planet.

• A planet has moons, while a dwarf planet does not.

• A planet orbits a star, while a dwarf planet orbits a planet.

• A planet has cleared its orbital path of other objects, while a dwarf planet has not.

Multiple Choice

What is the main relationship that distinguishes a moon from a planet?

• A moon is smaller than a planet.

• A moon orbits a planet, while a planet orbits the sun.

• A planet is a celestial object, while a moon is not.

• A planet is solid, while a moon is made of gas.

Multiple Choice

Imagine a newly discovered celestial object that orbits the sun, but its path is cluttered with many other small objects. Based on this information, how would this object most likely be classified?

• A planet

• A dwarf planet

• A moon

• An asteroid

Asteroids, Meteors, and Comets

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Asteroids

• ​Asteroids are rocky objects that are too small to be called planets.

• ​​They orbit the Sun, mostly in the asteroid belt between Mars and Jupiter.

• ​The asteroid belt separates the inner planets from the outer planets.

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Meteors

• ​A meteoroid is a rocky object that is smaller than an asteroid.

• ​​A meteor is a meteoroid that burns up in Earth's atmosphere.

• ​A meteorite is a piece of a meteoroid that lands on Earth.

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Comets

• ​A comet is a small mass of dust and ice that orbits the Sun.

• ​​As it nears the Sun, it develops a visible cloud called a coma.

• ​It also forms a tail of dust and gas pointing away from the Sun.

Multiple Choice

What is the primary difference in composition between an asteroid and a comet?

• Asteroids are mainly rock, while comets are mainly ice and dust.

• Asteroids are made of gas, while comets are made of rock.

• Asteroids orbit planets, while comets orbit the Sun.

• Asteroids have visible tails, while comets do not.

Multiple Choice

What is the correct sequence to describe a piece of a rocky object from space as it encounters Earth?

• It is a meteoroid in space, becomes a meteor in the atmosphere, and then a meteorite if it lands on Earth.

• It is a meteor in space, becomes a meteoroid in the atmosphere, and then a meteorite if it lands on Earth.

• It is an asteroid in space, becomes a meteor in the atmosphere, and then a comet if it lands on Earth.

• It is a meteorite in space, becomes a meteor in the atmosphere, and then a meteoroid if it lands on Earth.

Multiple Choice

A comet develops a coma and a tail as it nears the Sun. What would most likely happen to the comet as it travels away from the Sun and back towards the asteroid belt?

• Its coma and tail would shrink and become less visible.

• It would get larger and brighter.

• It would likely turn into an asteroid.

• Its tail would start to point toward the Sun.

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Common Misconceptions

Misconception	Correction
All objects in the solar system orbit the Earth.	All planets and other objects in the solar system orbit the Sun.
Planetary orbits are perfect circles.	Planetary orbits are elliptical, or oval-shaped.
'Shooting stars' are actually stars.	‘Shooting stars’ are meteors burning up in Earth's atmosphere.
The Sun is not a star.	The Sun is a medium-sized star.

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Summary

• Our solar system is heliocentric, with the Sun at its center.

• It has four rocky inner planets and four gas giant outer planets.

• Planets clear their orbits, but dwarf planets, asteroids, and comets do not.

• All planets rotate on an axis and revolve in an orbit around the Sun.

Poll

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

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