The solar system is contained in the universe. The universe is unimaginably big that not all of it can be seen. An object that moves through the space of the universe will likely do so forever. The solar system consists of all the stars, planets, moons or satellites, comets, meteoroids, asteroids and interplanetary medium. (The interplanetary medium are the small scattered particles that exists between the planets and other constituent bodies of the solar system. It's consists mainly of gas and dust). The sun (which is over 300,000 times bigger that the earth) is a star; in fact, it is an average sized star. This will imply that there are other stars that are bigger than the sun. The closest star to the sun is called Proxima Centauri with a distance of about over 4.3 light years away from it. The sun is the greatest source of light and heat in the universe and it is considered to be one of the factors that make the existence of life possible on earth.
Note: Our galaxy (called the Milky Way) contains over 220 billion stars and it’s only one of the billions of galaxies in the observable universe.
All the planets (including most of the planet’s satellite) and asteroids revolve round the sun. This orbital plane around the sun on which the planets revolve is called ecliptic. For instance, the average distance between the earth and the sun is about 149.6 million kilometers and it will take the earth 3651/4 days or 1 year to make a complete orbit (revolve) round the sun. This process is referred as the revolution of the earth and is responsible for the seasonal changes we experience on earth.
Note: A satellite is a body that revolves round (or orbit) the earth or another planet.
We have 13 planets that make up the solar system of which only 8 of them have been officially categorized.
The planets are listed below according to their relative distance from the sun:
The 5 uncategorized planets
- Has an average distance of about 5.91 billion kilometer from the sun.
- Earth is about 400 times bigger than pluto.
- Has 3 natural satellites.
The categorized planets can be group under the following headings
Terrestrial or Rocky Planets: They are Mercury, Venus, Earth and Mars. They are called terrestrial or rocky planets for the following reasons:
Gas or Jovian Planets: They include Jupiter, Saturn, Uranus, and Neptune. They have the following features:
Note: Venus Earth and Mars have atmospheres containing oxygen while mercury barely has an atmosphere. Read our article on atmosphere HERE
Small Planets: They have a diameter lesser that 13,000km. They include Mercury, Venus, Earth and Mars.
Giant Planets: Also referred to as the gas giants, they have a diameter greater that 48,000km. The gas giants include Jupiter, Saturn, Uranus and Neptune.
Inner planets: They are closer to the sun. They include Mercury, Venus, Earth and Mars.
Outer planet: They are farther away from the sun. They include Jupiter, Saturn, Uranus, Neptune.
Inferior planets: They appear to be closer to the sun than the earth. When viewed from the earth, they do not always appear in full view. They include Mercury and Venus.
Superior planets: They appear to be farther away from the sun than the earth. They will always appear in full view from the earth.
Classical Planets: They were discovered a very long time ago and can be seen without a telescope. They include Mercury, Venus, Earth, Mars, Jupiter and Saturn.
Modern planets: They were discovered in recent times and cannot be seen with an unaided eye. They are Uranus and Neptune.
Topics in GeographyTypes of Rocks Types and Branches of Geography Layers and Composition of the Atmosphere The Solar System