The Solar System — Planets, Sun & Facts Explained
Key Points At A Glance
- The solar system is the Sun and everything that orbits it.
- The Sun is a star holding over 99% of the system's mass.
- There are eight planets, kept in orbit by the Sun's gravity.
- Inner planets are small and rocky; outer planets are gas and ice giants.
- The asteroid belt lies between the inner and outer planets.
- It also includes moons, dwarf planets, asteroids and comets.
Look up at the night sky and you are looking at our cosmic neighbourhood — the solar system. It is home to our planet, seven other planets, dozens of moons, and a giant star at the centre that makes life possible. Let's take a simple tour of it, planet by planet.
What Is the Solar System?
The solar system is the Sun and everything that orbits around it — held together by the Sun's powerful gravity. This includes eight planets, their moons, dwarf planets, asteroids, comets and dust.
It formed about 4.6 billion years ago from a giant cloud of gas and dust.
The Sun — The Star at the Centre
The Sun is a huge ball of hot, glowing gas at the heart of the solar system. It makes up more than 99% of the system's total mass, and its gravity keeps all the planets in orbit. The Sun gives us light and heat, without which life on Earth could not exist.
The Eight Planets in Order
Moving outward from the Sun, the eight planets are:
- Mercury — the smallest planet and closest to the Sun.
- Venus — the hottest planet, covered in thick clouds.
- Earth — our home, the only planet known to support life.
- Mars — the "Red Planet", with iron-rich red soil.
- Jupiter — the largest planet, a giant ball of gas.
- Saturn — famous for its beautiful rings.
- Uranus — an ice giant that spins on its side.
- Neptune — the farthest planet, cold and windy.
A common trick to remember the order is the sentence: "My Very Easy Method Just Speeds Up Naming."
Inner and Outer Planets
The planets fall into two groups:
- Inner planets (Mercury, Venus, Earth, Mars) — small, rocky and solid.
- Outer planets (Jupiter, Saturn, Uranus, Neptune) — huge, made mostly of gas and ice.
Between these two groups lies the asteroid belt, a region full of rocky objects.
Other Members of the Solar System
- Moons — natural satellites that orbit planets. Earth has 1; Jupiter has dozens.
- Dwarf planets — small round bodies like Pluto, which was reclassified from a planet in 2006.
- Asteroids — rocky objects, mostly in the asteroid belt.
- Comets — icy bodies that grow a glowing tail when they come near the Sun.
Amazing Solar System Facts
- A day on Venus is longer than its year.
- Jupiter is so big that all other planets could fit inside it.
- Saturn would float in water because it is so light for its size.
- Light from the Sun takes about 8 minutes to reach Earth.
Important Exam Questions
- Name the eight planets in order from the Sun.
- What keeps the planets in orbit around the Sun?
- What is the difference between inner and outer planets?
- Why is Pluto called a dwarf planet?
Quick Summary
- The solar system is the Sun and everything orbiting it.
- There are eight planets, held in orbit by the Sun's gravity.
- Inner planets are rocky; outer planets are gas and ice giants.
- It also contains moons, dwarf planets, asteroids and comets.
Space becomes exciting when you connect facts to the night sky, so try spotting a planet or the Moon tonight. To remember the planet order and facts before an exam, use the methods in How to Memorize Faster. Explore more Science notes and all our study notes any time.
Frequently Asked Questions
The solar system is the Sun and all the objects that orbit it, including eight planets, their moons, dwarf planets, asteroids and comets — all held together by the Sun's gravity.
From the Sun outward, they are Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune.
The Sun's powerful gravity keeps all the planets moving in their orbits around it.
In 2006, Pluto was reclassified as a dwarf planet because it is small and has not cleared other objects out of its orbital path, unlike the eight major planets.
Jupiter is the largest planet. It is a gas giant so big that all the other planets could fit inside it.
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