The Solar System
Journey through the eight planets, asteroids, and comets that make up our solar neighbourhood.
Our Solar System
Our solar system consists of the Sun (a star) and everything that orbits around it -- eight planets, dwarf planets, moons, asteroids, and comets. The Sun's gravity holds everything in place.
The Eight Planets (in order from the Sun)
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Sun
Mercury
Venus
Earth
Mars
Jupiter
Saturn
Uranus
Neptune
Inner vs Outer Planets
Inner Planets (Rocky)
Closer to the Sun, smaller, made of rock and metal, have few or no moons.
- Mercury -- Smallest planet, closest to Sun, no atmosphere, extreme temperatures
- Venus -- Hottest planet (thick atmosphere traps heat), spins backwards, similar size to Earth
- Earth -- The only planet known to have liquid water and life, 1 moon
- Mars -- "The Red Planet" (iron oxide dust), has 2 small moons, thin atmosphere
Outer Planets (Gas/Ice Giants)
Farther from the Sun, much larger, made of gas and ice, have many moons and rings.
- Jupiter -- Largest planet, Great Red Spot (giant storm), 95+ moons
- Saturn -- Famous for its stunning rings (ice and rock), 146+ moons
- Uranus -- Tilts on its side, ice giant, blue-green colour, 28 moons
- Neptune -- Farthest planet, ice giant, strongest winds in the solar system, 16 moons
Other Objects in the Solar System
Asteroids
Rocky objects orbiting the Sun, mostly found in the asteroid belt between Mars and Jupiter.
Comets
Balls of ice, dust, and rock. When they pass near the Sun, they develop a glowing tail.
Dwarf Planets
Smaller bodies like Pluto, Eris, and Ceres. Too small to be full planets.
Key Vocabulary
Orbit
The curved path one object takes around another due to gravity (e.g. Earth orbits the Sun).
Solar System
The Sun and all the objects that orbit around it, including planets, moons, asteroids, and comets.
Gravity
The force that pulls objects toward each other. The Sun's gravity keeps the planets in orbit.
Atmosphere
The layer of gases surrounding a planet. Earth's atmosphere has the air we breathe.
Asteroid
A small rocky object that orbits the Sun, mostly found between Mars and Jupiter.
Comet
An icy body that, when near the Sun, develops a visible tail of gas and dust.
Worked Examples
Which planet is closest to the Sun, and which is farthest?
Step 1: Recall the order: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune.
Answer: Mercury is closest to the Sun. Neptune is farthest from the Sun.
Why is Venus hotter than Mercury, even though Mercury is closer to the Sun?
Step 1: Mercury has almost no atmosphere, so heat escapes easily.
Step 2: Venus has a very thick atmosphere made of carbon dioxide, which traps heat (like a greenhouse).
Answer: Venus's thick atmosphere creates a greenhouse effect, trapping heat and making it the hottest planet at about 465 degrees C.
What is the difference between an asteroid and a comet?
Asteroids: Made of rock and metal. Found mostly in the asteroid belt. No tail.
Comets: Made of ice, dust, and rock. When they approach the Sun, the ice melts and creates a glowing tail.
Knowledge Check
Select the correct answer for each question. Click "Check Answer" to see if you are right.
Question 1
What is the largest planet in our solar system?
Question 2
Which planet is the 4th from the Sun and known as "The Red Planet"?
Question 3
What keeps the planets orbiting around the Sun?
Question 4
Which planet is famous for its rings?
Question 5
Put these planets in order from closest to farthest from the Sun: Earth, Mercury, Mars, Venus
Key Concepts Summary
- ●The 8 planets in order: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune.
- ●Inner planets (Mercury-Mars) are small and rocky; outer planets (Jupiter-Neptune) are large gas or ice giants.
- ●The Sun's gravity holds the solar system together, keeping planets in orbit.
- ●Asteroids are rocky, comets are icy with tails, and dwarf planets (like Pluto) are smaller bodies.
- ●Earth is the only known planet with liquid water and life.