What is the Solar System?


The earth is not alone in space: people have long been observing the sun, moon and stars in the sky. They discovered early on that some stars are moving. These wandering stars were observed and their paths followed. But for a long time their movements were not understood – until about five hundred years ago a man by the name of Nicolas Copernicus solved the riddle. The earth and the “wandering stars” are actually planets, all orbiting the sun at different distances.

There are eight planets in our solar system. In order to remember their names in the correct order, an acronym can be used. An acronym is made up of the first initial of each planet’s name. For the planets, an acronym would be: MVEMJSUN. To remember the term necessary vowels should be added. Eventually, it might sound like “Move-em-jason” if it were spoken out loud.

How many planets in our solar system?

Our solar system consists of the sun, its eight planets and their moons, the dwarf planets and millions of small bodies such as asteroids and comets. All of which orbit the sun. The sun’s gravitational force holds all these celestial bodies together and forces them to orbit around it. The moons are also part of the solar system – but they are held by the gravitational pull of the planets.

8 planets of the solar system:

Planet Type Distance from the sun (AU) Period of revolution Period of rotation Mass (earth=1) Diameter (earth=1) Number of confirmed satellites
Mercury Rocky planet 0.39 88 days 59 days 0.06 0.38 0
Venus Rocky planet 0.72 225 days 243 days 0.82 0.95 0
Earth Rocky planet 1 365 days 24 hours 1 1 1
Mars Rocky planet 1.52 687 days 25 hours 0.11 0.53 2
Jupiter Gas giant 5.2 12 years 10 hours 317.89 11.19 63
Saturn Gas giant 9.54 29 years 10 hours 95.15 9.44 61
Uranus Ice giant 19.2 84 years 18 hours 14.54 4.1 27
Neptune Ice giant 30.06 165 years 18 hours 17.23 3.88 14

Source: NASA

Mercury, Venus, Earth and Mars are the four inner planets. They have a solid surface made of rock and are still relatively close to the sun – only a few hundred million kilometres.

Further out, at a distance of about one to 4.5 billion kilometres from the sun, the outer planets orbit: Jupiter, Saturn, Uranus and the most outward, Neptune. They consist of gas (especially hydrogen and helium) and are much larger than the inner planets. Jupiter and Saturn are about ten times the size of Earth, which is why they are called the gas giants.

How the solar system was formed?

This is related to how the sun have formed: a cloud of gas and dust contracted by its own gravity and became a star. However, not all material from this cloud was “built into” the star – about one percent remained. And when the sun began to shine, its radiation pushed the rest of the matter outwards.

The light gases were pushed far out, the heavier dust and rock remained near the sun. Over time, these planets were created from these dust and gas clouds. That is why there are gas planets outside in the solar system, rock planets further inside – including our earth – and the sun in the very center. It contains somewhere between 99.8% and 99.9% of the mass of the solar system and holds everything together with its gravity.

Is our solar system unique or rare?

No. Our solar system is not the only solar system in space. On the contrary: there are many billions of other solar systems, the planets of which in turn revolve around other suns. Our solar system is roughly 4.57 billion years old and has emerged from the collapse of a huge hydrogen cloud.

Planets of our solar system: interesting facts

Eight planets are orbiting the sun in our solar system. Their sizes and distances are only hinted at here – in reality the giant planets Saturn and Jupiter are about ten times the diameter of the earth, the sun is more than a hundred times larger. The sun’s atmosphere (the photo-sphere) is approximately 5,500 degrees Celsius, an it is 15 million degrees Celsius hot at the core. It is 750 times as heavy as all the planets combined and could absorb the Earth a million times. In the event of strong sun outbreaks, it ejects up to ten billion tons of gas into space.


Mercury is the smallest planet in our solar system. It has the greatest temperature differences between day and night: over 500 degrees. An interesting fact: Mercury is slowly shrinking because it has a large iron core that contracts.


Probably the most hellish planet in the solar system. Due to the dense atmosphere of carbon dioxide, the temperatures on Venus rise to 460 degrees during the day. Rain of caustic sulfuric acid falls from thick clouds, and the ground is littered with volcanoes.


Earth is the only planet that supports life in our solar system. It contains solid (ice), liquid and gaseous water (vapor). And sometimes a spectacular solar eclipse where the sun disappears behind the moon can be observed from earth.


Mars’ 27 kilometre high Olympus Mons is the highest mountain in the solar system. More than eight kilometres deep Valles Marineris on Mars is the largest canyon system. Also, tornado-like dust swirls with a diameter of one kilometre take place on the red planet.


The largest planet has the shortest days (9.8 hours) and the longest-lasting storm in the solar system. Its enormous red spot has been swirling for 340 years. In addition, Jupiter probably has the most moons, including the largest and most massive of the Solar System’s moons – Ganymede.


Saturn has a unique ring system. Its particles are made almost entirely of water ice, with a trace of rocky material. Some of Saturn’s moons consist entirely of frozen water. Lightning on Saturn is a million times stronger than on Earth and up to 100 meters wide.


Uranus has the most unusual seasons pattern in the solar system. Because Uranus’ North Pole points to the sun, it stays bright for around 40 years in summer. It may also rain diamonds. Researchers believe the stones could form from methane gas in Uranus’ atmosphere.


Nobody is further from the sun than Neptune. Extreme storms sweep over Neptune, with gusts of over 2000 kilometres per hour. Also, there are active ice volcanoes on the its moon, Triton. They spit out nitrogen at minus 220 degrees.


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