Planets

Planets

Middle School

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Learning Objectives

• Describe the basic structure of our solar system, including the Sun and planets.

• Compare the differences between the rocky inner planets and the gas giant outer planets.

• Name the eight planets of our solar system in their correct order from the Sun.

• Recall at least one unique and interesting feature for each of the eight planets.

Key Vocabulary

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Terrestrial Planets

The four inner planets which have hard, rocky surfaces and are smaller and closer to the sun.

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Jovian Planets

The four outer planets, also known as Gas Giants, which are large and made mostly of gasses.

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Asteroid Belt

A region between Mars and Jupiter where most of the solar system's asteroids are found orbiting the sun.

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Dwarf Planet

A celestial body that is smaller than a planet and may share its orbital path with other objects.

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Comet

A cosmic snowball of frozen gases, rock, and dust that orbits the Sun, developing a tail when close.

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What is the Solar System?

• The solar system is 4.5 billion years old, containing many different celestial objects.

• It includes the Sun, eight planets, moons, dwarf planets, asteroids, and comets.

• The Sun is the largest object, made of hydrogen and helium gas.

• The eight planets are Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune.

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Multiple Choice

What are the two main components of the Sun, which is the largest object in our solar system?

• Iron and Nickel

• Rock and Ice

• Hydrogen and Helium

• Oxygen and Carbon Dioxide

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The Inner, Terrestrial Planets

Mercury

• As the planet closest to the sun, Mercury has no real atmosphere to regulate its temperatures.

• It experiences extreme temperature swings, from 800°F during the day to -180°F at night.

• Its magnetic field interacts with solar winds, which is known to create powerful magnetic tornadoes.

Venus

• Venus is the hottest planet in our solar system due to a runaway greenhouse effect.

• Its day is longer than its year because it has a slow, backward (retrograde) rotation.

• Its thick atmosphere of carbon dioxide traps heat, causing extreme surface temperatures of around 880°F.

Multiple Choice

Which inner planet is known for its extreme temperatures and which for its retrograde rotation?

• Mars and Earth

• Mercury and Venus

• Venus and Mercury

• Earth and Mars

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The Inner Planets: Earth & Mars

Earth

• ​Earth is the only planet currently known to have liquid water on its surface.

• ​​Its atmosphere and liquid water make it the only world known to support life.

• ​The planet is protected by a strong magnetic field and has one large moon.

Mars

• ​Mars is called the 'Red Planet' because of the iron oxide, or rust, on its surface.

• ​​It is about half the size of Earth and has a very thin atmosphere.

• ​It has two small moons and the solar system's largest volcano, Olympus Mons.

Multiple Choice

What is the nickname for Mars and what geological feature is it famous for?

• The Blue Marble, its oceans

• The Ringed Planet, its rings

• The Red Planet, the volcano Olympus Mons

• The Hot Planet, its acid clouds

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The Outer, Jovian Planets

Jupiter

• Jupiter is the largest planet in the solar system, made mostly of hydrogen and helium gas.

• It rotates faster than any other planet and has the strongest magnetic field in the solar system.

• Jupiter has dozens of moons, including Europa, which may have an ocean under its icy crust.

Saturn

• Saturn is the second-largest planet and is most famous for its large and complex ring system.

• It is the least dense planet in our solar system and would actually float in water.

• Like Jupiter, Saturn has many moons, with its largest being Titan, a world with a thick atmosphere.

Multiple Choice

Which of these is a key characteristic of the Jovian planets like Jupiter and Saturn?

• They have solid, rocky surfaces for landing.

• They are smaller and denser than Earth.

• They are large, gaseous, and have many moons.

• They are closer to the Sun than Mars.

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The Ice Giants & Other Regions of the Solar System

The Ice Giants

• Uranus and Neptune are made of a hot, dense fluid of materials like water, methane, and ammonia.

• Uranus is tilted at a 98-degree angle, causing extreme seasons with 42 years of light and then darkness.

• Neptune, the smallest gas planet, was discovered using mathematical calculations rather than direct observation from Earth.

Beyond Neptune

• The Kuiper Belt is a donut-shaped region of many icy bodies located just beyond the orbit of Neptune.

• Far beyond the Kuiper Belt lies the Oort Cloud, a giant spherical shell of icy debris and objects.

• The Kuiper Belt and the Oort Cloud are both known to be the original sources of comets.

Multiple Choice

Why is Uranus unique among the planets?

• It is the largest planet.

• It is the least dense planet.

• It is tilted on its side at a 98-degree angle.

• It was discovered using math.

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Other Solar System Objects

Asteroids & Meteors

• Asteroids are rocky remnants from the early solar system, mostly found in a belt between Mars and Jupiter.

• Meteoroids are 'space rocks' that become meteors, or ‘shooting stars,’ when burning up in our atmosphere.

• If a piece of the meteoroid survives and hits the ground, it is then called a meteorite.

Dwarf Planets

• Dwarf planets are celestial bodies, smaller than planets, that also orbit the Sun.

• Unlike planets, they share their orbit with other objects, like Pluto does with Neptune.

• Ceres is another example of a dwarf planet and is the largest object in the asteroid belt.

Multiple Choice

What is the main difference between a meteoroid and a meteorite?

• A meteoroid is in space, a meteorite has hit the ground.

• A meteoroid is made of ice, a meteorite is made of rock.

• A meteoroid is in the asteroid belt, a meteorite is in the Kuiper Belt.

• A meteoroid is a 'shooting star', a meteorite is a space rock.

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Common Misconceptions

Misconception	Correction
Pluto is still the ninth planet.	Pluto is a dwarf planet because it has not cleared its orbital path.
You can land a spaceship on Jupiter or Saturn.	Gas giants have no solid surface; spacecraft would be crushed by the pressure.
The asteroid belt is a crowded, dense field of rocks.	The space between asteroids is vast; the belt is mostly empty space.
All planets rotate in the same direction.	Venus spins backward compared to most other planets.

Multiple Choice

Based on their composition, why are the inner planets smaller and denser than the outer planets?

• They formed in a colder region of the solar system.

• They are made of heavier rock and metal, while outer planets are made of lighter gases.

• They have stronger gravity which compresses them more.

• They spin slower than the outer planets.

Multiple Choice

How does the extreme tilt of Uranus affect its seasons compared to Earth's?

• Uranus has no seasons because of its tilt.

• Its seasons are shorter and more extreme than Earth's.

• Its seasons are extremely long, with decades of continuous daylight followed by decades of darkness.

• Its seasons are mild and similar to Earth's all year round.

Multiple Choice

A scientist discovers a new celestial body. It is large, gaseous, has many moons, and a faint ring system. Where in the solar system would you predict this object is located and why?

• Between Mars and Jupiter, because that is where the asteroid belt is.

• Close to the sun, because it is large.

• In the outer solar system beyond Mars, because its features match those of the Jovian planets.

• In the Oort cloud, because it is gaseous.

Multiple Choice

Where is the Kuiper Belt located?

• Between Mars and Jupiter

• Just beyond Neptune’s orbit

• Surrounding the entire Solar System

• Between Earth and Venus

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Summary

• Our solar system is centered around the Sun and contains eight planets.

• The four inner planets are rocky and smaller, while the four outer planets are gaseous and large.

• Each planet has unique characteristics, such as Venus's retrograde rotation and Uranus's extreme tilt.

• The solar system also contains dwarf planets, the asteroid belt, the Kuiper Belt, and the Oort Cloud.

Poll

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

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