The solar system

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Lesson notes

The Solar System Overview

The solar system consists of a **star** (the **Sun**) and **eight planets**.
The **Sun** contains most of the mass of the solar system.
**Gravitational forces** keep the planets in orbit around the Sun.
The Sun's surface temperature is around **6000°C**.

Planets in Order from the Sun

1. **Mercury** – smallest planet, closest to the Sun.
2. **Venus** – has a carbon dioxide atmosphere, hottest planet.
3. **Earth** – only known planet with life.
4. **Mars** – colder than Earth, further from the Sun.
5. **Jupiter** – largest planet, Great Red Spot (storm lasting >400 years).
6. **Saturn** – second largest, rings made of ice and rock.
7. **Uranus** – third largest, rotates on its side.
8. **Neptune** – furthest planet, lowest average temperature.

Types of Planets

**Terrestrial (rocky) planets**: Mercury, Venus, Earth, Mars (closest four).
**Gas giants**: Jupiter and Saturn.
**Ice giants**: Uranus and Neptune.
**Pluto** is a **dwarf planet**, beyond Neptune.

Temperature and Gravity

Planet temperature generally **decreases** with distance from the Sun.
**Venus** is an exception – its CO₂ atmosphere traps heat (greenhouse effect).
**Neptune** has the lowest average temperature (furthest from Sun).
**Jupiter** has the largest gravitational field strength (25 N/kg).

Mnemonic for Planet Order

My Very Easy Method Just Speeds Up Naming (Planets).
Corresponds to: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune.

Diagram of the solar system showing the Sun and eight planets in order, with orbits.

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Practice questions

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1.How many planets are there in the solar system?
Easy
- A8
- B7
- C9
- D10
2.Which of the following are the four terrestrial planets?
Easy
- AMercury, Venus, Earth, Mars
- BMercury, Venus, Earth, Jupiter
- CVenus, Earth, Mars, Jupiter
- DEarth, Mars, Jupiter, Saturn
3.Which planets are the gas giants?
Easy
- AJupiter and Saturn
- BUranus and Neptune
- CSaturn and Uranus
- DJupiter and Neptune
4.Which planets are the ice giants?
Easy
- AUranus and Neptune
- BJupiter and Saturn
- CSaturn and Uranus
- DNeptune and Pluto
5.What is the correct order of planets from the Sun outward?
Medium
- AMercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune
- BMercury, Venus, Earth, Mars, Saturn, Jupiter, Uranus, Neptune
- CVenus, Mercury, Earth, Mars, Jupiter, Saturn, Neptune, Uranus
- DMercury, Earth, Venus, Mars, Jupiter, Saturn, Uranus, Neptune
6.Which planet has the highest average surface temperature and why?
Medium
- AVenus, because of its carbon dioxide atmosphere
- BMercury, because it is closest to the Sun
- CVenus, because it is closest to the Sun
- DJupiter, because it is a gas giant
7.What object contains most of the mass in the solar system?
Easy
- AThe Sun
- BJupiter
- CEarth
- DSaturn
8.What force keeps planets in orbit around the Sun?
Easy
- AGravitational force
- BMagnetic force
- CCentrifugal force
- DNuclear force

Revision notes

## The Solar System - The solar system consists of a star (the Sun) and eight planets. The Sun contains most of the mass, so its gravity keeps planets in orbit. - Surface temperature of the Sun: ~6000°C. ### Planets in order from the Sun: 1. **Mercury** – smallest, closest to Sun. 2. **Venus** – carbon dioxide atmosphere (greenhouse gas), hottest planet. 3. **Earth** – only known planet with life. 4. **Mars** – colder than Earth. 5. **Jupiter** – largest planet, largest gravitational field strength (25 N/kg), Great Red Spot (storm lasting >400 years). 6. **Saturn** – second largest, rings made of ice and rock. 7. **Uranus** – third largest, rotates on its side. 8. **Neptune** – furthest from Sun, lowest average temperature. - **Pluto** is a dwarf planet, beyond Neptune. - Mnemonic: **M**y **V**ery **E**asy **M**ethod **J**ust **S**peeds **U**p **N**aming (Planets). ### Types of planets: - **Terrestrial (rocky) planets**: Mercury, Venus, Earth, Mars (closest four). - **Gas giants**: Jupiter, Saturn. - **Ice giants**: Uranus, Neptune. - Generally, temperature decreases with distance from Sun, except Venus (due to greenhouse effect). **Key fact**: Gravitational force keeps planets in orbit around the Sun.

Solar system: A star (the Sun) and the eight planets that orbit it, plus other objects.
Terrestrial planets: The four rocky planets closest to the Sun: Mercury, Venus, Earth, Mars.
Gas giants: The large planets made mostly of gas: Jupiter and Saturn.
Ice giants: The planets made mostly of ice: Uranus and Neptune.
Dwarf planet: A celestial body that orbits the Sun but is not a full planet, e.g., Pluto.
Gravitational force: The force that keeps planets in orbit around the Sun.
Great Red Spot: A storm on Jupiter that has lasted for over 400 years.

Flashcards

How many planets are in the solar system?

There are eight planets.

What is the Sun's surface temperature?

Around 6000°C.

Which object contains most of the mass in the solar system?

The Sun.

What force keeps planets in orbit around the Sun?

Gravitational force.

List the planets in order from closest to furthest from the Sun.

Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune.

What is the smallest planet and closest to the Sun?

Mercury.

Which planet has a carbon dioxide atmosphere and is the hottest?

Venus.

Why is Venus the hottest planet?

Its carbon dioxide atmosphere is a greenhouse gas, trapping heat.

Which planet is known to have life?

Earth.

Which planet is much colder than Earth because it is further from the Sun?

Mars.

What is the largest planet in the solar system?

Jupiter.

What is Jupiter's Great Red Spot?

A storm that has lasted for over 400 years.

What is Jupiter's gravitational field strength?

25 N/kg.

Which planet is second largest and has rings made of ice and rock?

Saturn.

Which planet rotates on its side?

Uranus.

Which planet is furthest from the Sun and has the lowest average temperature?

Neptune.

What is Pluto classified as?

A dwarf planet.

Name a mnemonic to remember the order of the planets.

My Very Easy Method Just Speeds Up Naming (Planets).

Which four planets are terrestrial (rocky)?

Mercury, Venus, Earth, Mars.

Which two planets are gas giants?

Jupiter and Saturn.

Which two planets are ice giants?

Uranus and Neptune.

How does planet temperature generally change with distance from the Sun?

Temperature generally decreases with distance from the Sun.

Which planet is an exception to the temperature-distance trend and why?

Venus, because its carbon dioxide atmosphere traps heat.

Which planet has the largest gravitational field strength?

Jupiter.

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