Outer space – endless expanses. We are on a mission to explore the planets in our solar system. Strange and wondrous worlds are waiting to be discovered and so we begin our journey near the center of our planetary system, the sun. From there we fly to the edge of our solar system and get to know our eight planets.
But before we start our journey, we have to ask ourselves what exactly constitutes a planet.
Planets – explanation
The question may sound a bit strange at first: Everyone knows what a planet is, right?
At least everyone has a rough idea of what a planet is, but even astronomers struggle with a precise definition. After all, planets come in all shapes, colors, and sizes. So where do you draw the line between planet and non-planet?
To the different celestial bodies to be able to classify anyway, has the IAU (International Astronomical Union) established the following definition of a planet in 2006:
A celestial body is considered according to the IAU planet designated if it meets the following three criteria:
- A planet moves in a orbit around one (or more) star(s).
- Its mass is so great that its gravity gives it the shape of a sphere gives.
- A planet it is dominant object in its orbit and cleared it of other celestial bodies.
However, there is also criticism of this definition, especially the third point. After all, there are about 100,000 asteroids orbiting the planet Jupiter around the sun.
That’s why you have one planetary discriminant introduced. It gives the ratio of the planet’s mass to the mass of other objects (other than moons) in its orbit. In short, the planet should be by far the most massive object in its orbit.
There are many different objects in our solar system, but only 8 of them meet the above criteria.
The 8 planets of our solar system
the eight planets revolve around our central star, the sun. From there we will start a journey in our virtual spaceship to explore the planets of our solar system.
1st planet: Mercury
The first planet is that Mercury: named after the Roman messenger of the gods. A fitting name for the fastest planet in our solar system. Because it is closest to the sun, it has the smallest orbit. A Mercury year lasts only 88 days.
A year is the number of days it takes for a planet to orbit the sun. So it takes the earth 365 days to go around the sun. In astrophysics, you also call this the sidereal orbital period.
Just like Earth, Mercury has one rock layer, but it has neither an atmosphere nor liquid water on the surface. This close to the sun would simply evaporate. After all, temperatures on Mercury can rise to 430°C during the day! During the night, however, the surface cools down to -170°C.
Figure 1: Planet Mercury Source: pixabay.com
Also, Mercury is the smallest planet our solar system. Its diameter is just 40% of the earth’s diameter. Some astronomers have even theorized that Mercury once had a moon of Venus was. This would explain why these two planets are the only planets in our solar system that do not have moons.
2nd planet: Venus
Next, we travel many thousands of miles to a planet you may have seen in the evening sky. the Venus is closest to Earth and shines so brightly that it was once thought to be a star: the evening or morning star.
In fact, however, Venus is one of them earth-like planets. It is only slightly smaller than Earth and has a rocky surface and an atmosphere. She was named after the Roman goddess of love. Sometimes it is also called «twin planet» of Earth. If we now go to the surface of Venus, you will find that these twins are very different after all.
Figure 2: Planet Venus Source: pixabay.com
the the atmosphere Venus is extremely dense and consists of almost 97% carbon dioxide (). Not only is there very high pressure there, but also extreme heat (up to 500°C) – caused by that greenhouse effect the high – concentration.
The same effect is causing man-made climate change on Earth. If you want to know more about the greenhouse effect, take a look at the associated learning set!
Another strange feature of Venus is that a Venusian day lasts longer than a Venusian year. A year on Venus lasts 5400 hours, while a Venusian day lasts about 5832 hours. This is due to the definition of day and year. In a year the planet moves around the sun once, in a day the planet rotates once on its own axis.
Venus rotates so slowly on its own axis that it can orbit the sun once in the meantime.
Did you know that there have been more missions to Mars than Venus, even though Venus is much closer to Earth? This is due to the extreme temperatures on Venus’ surface. Under these conditions, our technical devices only survive for a very short time.
In addition, Venus is almost always shrouded in a low cloud layer, which absorbs the signals from our space probes.
3rd Planet: The Earth
Next we fly past our home planet: the earth. It lies in the midst of the so-called habitable zone.
in one star system denotes the habitable zonethe range of distances from the central star in which the conditions for life as we know it are given: for example liquid water, moderate temperatures and protection from excessive radiation.
A star system includes all objects that are under the gravitational influence of one or more stars.
Earth fulfills all the characteristics of a planet in the habitable zone. It is over 70% covered with liquid water and has an average temperature of 15°C. In addition, the earth’s strong magnetic field protects us from too much cosmic radiation.
Figure 3: Planet Earth
The earth is that fourth smallest planet in the solar system and so far the only one from which we know that there is life. Like Mercury and Venus, the earth has a rocky surface under which there is a liquid core. In the middle is an iron core.
4th Planet: Mars
At the very edge of the habitable zone is the next planet on our journey through the solar system: The Mars – named after the Roman god of war due to its reddish hue. This color comes from the layer iron oxide dust on the surface of the planet (the planet rusts).
Mars is considered to be the planet most likely to be colonized by humans. But it won’t be that easy.
Mars is smaller than Earth and has a much smaller gravitational force, our human body is not used to this. Also, Mars only has one thin atmosphere, which, like Venus, consists primarily of carbon dioxide. being weak magnetic field also does not protect us sufficiently from the dangerous cosmic radiation.
However, a day on Mars is only 37 minutes longer than on Earth, and there is water in frozen form at the planet’s poles (perhaps even underground). Depending on where you are, temperatures on Mars range from a chilly -150°C to a comfortable +20°C.
By the way, Mars has two small moons: Phobos and Deimos.
Figure 4: Planet Mars
However, some scientists believe it is possible that we may one day live on Mars and until then NASA and other space agencies are busy broadcasting rover and probesto learn more about the red planet.
We have to travel very far to our next destination, because the distance between Mars and the next planet is very large. There is even one between them asteroid field.
5th planet: Jupiter
The fifth planet in our solar system was called Jupiter – named after the main god of Roman mythology. This is because Jupiter is the largest Planet of our solar system is – about 2.5 times as massive as all other planets combined! This time we won’t land on the surface of the planet, just explore it from a distance.
Jupiter does not have a solid surface – the whole planet resembles a huge one gas ball from hydrogen and helium. Only inside is the pressure so high that there is probably a solid core of ice and rock there. However, we cannot say for sure, after all, no one has ever penetrated so far.
Figure 5: Planet Jupiter
The bands and vortices you see on the surface are clouds and storms in the planet’s atmosphere. The different colors come from the different elements in the cloud bands. Perhaps the most striking feature of Jupiter is the Great Red Spot – a cyclone 1.5 Earths in diameter.
Jupiter has 79 known moons. The largest are Callisto, Io, Ganymede and Europa and were discovered by Galileo Galilei as early as 1610 (that’s why you call them Galilean moons). Some of the moons are the size of a small planet and some even have their own magnetic field.
Researchers have discovered conditions that could support life on some of Jupiter’s moons. Therefore, the moons of Jupiter have increasingly become the focus of research in recent years.
6th Planet: Saturn
Passing the largest planet in our solar system, we are approaching Saturn, whose most striking feature is its conspicuous rings. Just like Jupiter, Saturn is mostly composed of hydrogen and helium. Despite its size, it has a very low density, making it relatively light in relation to its dimensions.
Earth would fit inside Saturn about 764 times, yet the giant gas planet weighs 95 times as much as Earth.
Its core consists of ice and silicon. The pressure there is so high that hydrogen turns into a metallic form.
That’s why we won’t end up here either. Instead, let’s take a quick look at his ring system. In fact, it is made up of several rings rockswhich extend over hundreds of thousands of kilometers.
Figure 6: Planet Saturn
However, we do not know where exactly these rings came from. It is believed that they either date from the early days of planet formation or were once moons created by the tidal forces of Saturn were torn apart. By the way, Saturn also has more than enough moons. Astronomers have now been able to count 82 moons! The biggest of them is called titanium.
Saturn was named after the father of Jupiter in Roman mythology. This was not one of the gods, but one of the titans – hence the name of its largest moon.
7th Planet: Uranus
By now they have traveled quite a distance. It’s pretty cold that far from the sun. From here we only find ice worlds. The first of these ice worlds is Uranusthe third largest…