Subjects
Grades
The Solar System | Elementary
Concept sheet | Science and Technology
Grade
5-6
What Is the Solar System?
- The solar system is made up of the Sun and all the celestial bodies orbiting it.
- A celestial body is a natural object located in space, such as a planet, natural satellite or meteorite.
- Orbiting a celestial body means “following a curved path around it due to gravity.”
The solar system is located in a galaxy called the “Milky Way.”
Adapted from Triff, Shutterstock.com
In our solar system, there are several different types of celestial bodies:
- One star (the Sun)
- The telluric planets, also known as “terrestrial planets” (Mercury, Venus, Earth, Mars)
- The Jovian planets, also known as “gas giants” (Jupiter, Saturn, Uranus, Neptune)
- Natural satellites (e.g., the Moon)
- Other celestial bodies (dwarf planets, asteroids, etc.)
The Sun is at the centre of our solar system, and most other celestial bodies in the solar system orbit it directly. When a celestial body has completed a full orbit around the Sun, it is said to have completed a revolution.
What Is a Star?
- A star is a celestial body made up of plasma that produces heat and light.
- A body in the plasma state is composed of gases and particles called “electrons.”
The Sun is a star. The plasma that makes up the Sun is mainly composed of particles called “hydrogen” and “helium.”
In the Sun, hydrogen particles fuse to form helium particles. This fusion reaction releases a great deal of energy in the form of heat and light.
This heat and light played a major role in the emergence of life on Earth.
The Sun is often depicted as yellow to red. However, these colours come from the instruments used to observe it. In reality, the Sun is white.
Adapted from Artsiom P, Shutterstock.com
The Sun’s diameter is about 109 times greater than the Earth’s!
The Sun rotates on its own axis and revolves around the centre of the galaxy.
What Is a Planet?
A planet is a spherical celestial body that orbits around a star.
Planets do not emit light, and their orbits are clear. In other words, they do not have other celestial bodies of comparable size in their orbital zones, except for their natural satellites.
The planets in the solar system fall into two categories: telluric (or terrestrial) planets and Jovian planets (or gas giants).
The following table compares the Jovian and telluric planets.
| Telluric Planets | Jovian Planets |
|---|---|
| Surface mainly composed of rock | Surface mainly composed of gas |
| Smaller size | Larger size |
| Closer to the Sun | Farther from the Sun |
| Warmer (between approximately -175℃ and 430℃) | Cooler (between approx. -220℃ and -110℃) |
| Shorter revolution* (88 days to 2 years) | Longer revolution* (12 years to 165 years) |
*Revolution: Number of Earth days or years required to complete one orbit around the Sun.
Data source: Canadian Space Agency, 2020.[1]
Adapted from 24k-Production, Elena11, 24k-Production, Artsiom P, buradaki, Shutterstock.com
What Is a Natural Satellite?
A natural satellite is a naturally occurring celestial body that orbits a more massive celestial body.
In astronomy, we distinguish between natural satellites and artificial satellites. Artificial satellites are made by humans. For example, the International Space Station is an artificial satellite placed in orbit around our planet to carry out scientific experiments.
The Moon is a natural satellite orbiting the Earth. It is a naturally occurring celestial body that orbits the Earth, a more massive celestial body.
Adapted from 19 Studio, Shutterstock.com
The planets Mars, Jupiter, Saturn, Uranus and Neptune have several natural satellites.
In our solar system, the natural satellites of telluric planets have a surface made up mainly of rock, while the satellites of the Jovian planets have a surface made up of a mixture of rock and ice.
Note that although planets and stars orbit a heavier celestial body, they are not considered natural satellites.