Planet refers to a celestial body that orbits around the sun.
It is important to note that not every celestial body in space is considered a planet.
How is a planet defined?
In order to be classified as a planet, three distinct categories must be achieved.
The celestial body must orbit around the sun.
The celestial body must have enough mass for self-gravity in order to repress the rigid body forces and form a hydrostatic equilibrium shape (similar to a round shape).
The celestial body must clear the orbit around its solar system.
What is a dwarf planet and its difference to a planet?
A dwarf planet refers to a celestial body that orbits around the sun, having enough mass for self gravity in order to repress the rigid body forces and form a hydrostatic equilibrium shape (similar to a round shape).
However, compared to a planet, a dwarf planet has not completed its orbit around their solar system. A dwarf planet is not considered a satellite.
What is a satellite?
A satellite may refer to a moon, a planet, or a machine that orbits around a star or a planet. (E.g. Earth can be considered as a satellite, since it orbits around the sun.)
Typically, a satellite is referred to a machine that is sent into space and orbits around the Earth or other celestial bodies.
What is a solar system?
A solar system refers to the sun that has 8 to 9 planets orbiting around in the Milky Way Galaxy. There are about 210 planetary satellites (Known as the moons) that are named within the solar system, along with many asteroids, satellites, comets and icy bodies.
Planets within the solar system
There are currently 8 known planets that are orbiting the Sun in the solar system. The 4 planets that are rock-like are:
Planets that are found on the outer area of the solar system are known as gas giants (Jupiter and Saturn) and ice giants (Uranus and Neptune).
Dwarf planets are found after Neptune, one of the most popular dwarf planets is Pluto.
Planets that are found outside the solar system are named as exoplanets.
The Sun is the biggest celestial body in the solar system. Located at the centre of the solar system, it is a 4.5 billion-year-old star made up of hydrogen and helium. 1.3 million Earths are required to fit in within to achieve the volume of the Sun.
The distance between the Sun and the Earth is approximately 93 million miles (150 million kilometres) away.
The gravity of the Sun allows celestial bodies and other objects to stay in orbit within the solar system.
The temperature in the core of the Sun is found to reach as high as 15 million degrees Celsius. Strong eruptions and a steady stream of charged particles are radiated from the Sun, which changes the nature of the space within the solar system.
Mercury is the smallest and closest planet to the sun in the solar system. The size of the mercury is slightly bigger than the Moon of the Earth. It is the fastest planet to complete its orbit around the sun, taking about 88 days.
The sunlight from Mercury will be 7 times brighter than on Earth, and the size of the sun seen from Mercury will be 3 times larger. However, it is not the hottest planet in the solar system.
Venus is the second-closest planet to the Sun in the solar system. The density and size of Venus is similar to Earth, therefore gaining the nickname of the “Earth’s Twin”. However, Venus rotates backwards on its axis, where the Sun rises on the west and sets on the east.
Venus is the hottest planet in the solar system, with its dense atmosphere filled with carbon monoxide and permanently shrouded in clouds of sulphuric acid. This causes the heat in the planet to be trapped within, creating a greenhouse effect. The highest temperature of Venus is found to be 475 degree Celsius.
The colour of the Venus surface is rusty, filled with mountains and thousands of huge volcanoes. Some volcanoes are speculated to be active in Venus. The air pressure of Venus is similar to the pressure found in oceans depths on Earth.
Earth is the third planet from the Sun, the only planet in the solar system that is occupied by living beings. It is the 5th biggest planet in the solar system, with liquid water on the surface.
The name “Earth” is in German, known as “The Ground” in English. Other planets in the solar system are named after Greek and Roman gods and goddesses.
Mars is the fourth planet from the Sun in the solar system. The planet itself has an extremely thin atmosphere, while the surface is dusty, frigid, and deserted.
There are seasons in Mars, evidence from the polar ice caps, canyons and extinct volcanoes suggest that the planet was active previously.
Mars is one of the planets that are most explored in the solar system. Rovers were sent to roam about in the land of Mars, named as Curiosity and Perseverance. One lander (InSight) and a helicopter (Ingenuity) are sent to roam around the surface of Mars
Jupiter is the fifth and the biggest planet found in the solar system.
The stripes and swirls in Jupiter are frigid, stormy clouds of ammonia and water. The stormy clouds float in the atmosphere of hydrogen and helium. The red spot in Jupiter is a gigantic storm that has been occurring for hundreds of years.
Juno orbiter is the spacecraft that was sent to explore Jupiter.
Saturn is the sixth planet from the sun and is the second-biggest planet in the solar system. Saturn is surrounded by thousands of rings that are made of ice and rock chunks. The planet itself is made up of hydrogen and helium, similar to Jupiter.
Uranus is the seventh planet from the sun in the solar system. It was the first planet to be discovered using a telescope by William Herschel in 1781.
It is an ice giant that rotates nearly at a 90-degree angle in the orbit from its plane. This causes Uranus to appear as if it is spinning on its side.
Neptune is the eighth planet from the sun in the solar system. It is the furthest major planet orbiting around the Sun. The planet is filled with gloomy and frigid supersonic winds.
The distance between the Sun and Neptune is more than 30 times the distance between the Sun and the Earth. Neptune is the only planet that is not visible to the naked eye in the solar system.
The existence of Neptune was predicted by mathematics before being discovered in 1846. Voyager 2 is the only spacecraft that was sent to observe Neptune closely, before moving past the planet in 1989 and out of the solar system.
Pluto is a dwarf planet that is located in the Kuiper Belt, a region that is donut-shaped, filled with icy bodies outside the orbit of Neptune. Icy objects found in the Kuiper Belt are known as Kuiper Belt Objects (KBOs) or Trans-Neptunian Objects (TNOs).
Pluto is smaller than the Moon of the Earth. There are glaciers found in Pluto that are the size of Texas and Oklahoma. Pluto is found to have blue skies, spinning moons, tall mountains (as high as Rockies) and snow.
I hope the information available helps you to understand more about the planets that are in our solar system. As this article may serve as an aid to help you introduce different planets for your child to learn about it.