Our home in space
Our solar system occupies quite a modest place in the Universe. It’s a tiny part of our native galaxy, the Milky Way.
As well as our Sun, there are another 100 to 400 billion other stars here. You can imagine the Milky Way as a flat disc that rotates. It has a diameter of 120,000 light years, but it’s only around 1000 light years in thickness. At the centre is an enormous black hole. It is four million times as heavy as our sun.
Even the size of the Milky Way is barely conceivable for us humans. But it’s only a very tiny part of the entire Universe, which is made up of several hundred billion galaxies.
Our position in the Milky Way
Our Sun lies on the Orion arm of the Milky Way and orbits the centre of the galaxy at a distance of 25,000 to 28,000 light years. It takes 220 to 240 million years for the Sun to complete a single orbit around the central black hole Sagittarius A*– and that’s at the breath-taking orbital speed of around 800,000 km/h.
Our solar system
The solar system in which we live was formed around 4.5 billion years ago from a disc of swirling gas and dust. It consists of one sun and eight planets. Planets are large, round celestial bodies that orbit a star and do not emit their own light. They orbit on their own path alone, because their relatively large mass means that they attract all other heavenly bodies in their way. The Romans gave the planets their names, which they still have in many European languages today.
The Sun
Like all light-emitting stars, our Sun radiates energy. This energy originates from reactions inside the Sun, in which the hydrogen converts to helium in a process called nuclear fusion. These processes are the source of almost all the energy available on Earth.
For a long time, people were convinced that the Earth was the centre of the Universe. Astronomer and mathematician Nicolaus Copernicus rejected that idea in 1514. He was certain that the planets and therefore the Earth too were orbiting the Sun. A shocking idea! It wasn’t until the 17th century that this model gradually became accepted.
© Max Planck Society
Mercury
Mercury completes an orbit of the Sun in just 88 days. That was why the Romans named it after the speedy messenger god, Mercury. The smallest planet in our solar system has an extremely thin atmosphere. For this reason its surface temperature varies between −173 degrees Celsius in the night and +427 degrees Celsius in the sunlight.
Venus
Viewed from Earth, no other “star” sparkles more brightly than Venus. It’s the first celestial object to become visible in the evening, and the last one to disappear in the morning. For this reason it’s also known as the Evening Star or Morning Star. But Venus doesn’t emit its own light either. It reflects the light of the Sun, like all the other planets.
Earth
What good luck that Earth is just the right distance away from the Sun. It’s only thanks to this that life was able to develop on Earth. Any nearer to the Sun would be too hot, and further away would be too cold. It’s only in this habitable zone that water can stay in a liquid state for any length of time. That’s a prerequisite for the development of life as we know it.
Mars
Mars is made of ferrous rock. Its orange colour is nothing other than rust! The largest volcano on Mars is over 20 kilometres high. The tallest mountain on Earth, Mount Everest, would look quite small beside it at 8848 metres. Several Mars robots have already conducted geological investigations on the planet.
Jupiter
Jupiter is by far the largest planet of our solar system. The giant gas planet has almost the same composition as the Sun – but it’s still too light to ignite and become a star in its own right. Jupiter has at least 79 moons.
Saturn
Saturn’s famous rings consist of fragments of ice and rock in different sizes. In total there are over 100,000 rings in a flat disc. Other planets have rings too, but they aren’t as clearly defined and therefore can’t be seen so well.
Uranus
The ice planet Uranus was only discovered by the German-British astronomer and musician Wilhelm Herschel in 1781. Uranus has at least 27 moons, many of which are named after characters in the works of William Shakespeare.
Neptune
Neptune is the only planet that cannot be seen with the naked eye from Earth. As a result it wasn’t discovered until 1846 by astronomer Johann Gottfried Galle. Before that the mathematician Urbain Le Verrier had calculated the existence and approximate position of this planet. So Galle knew what to look out for.
Even the size of the Milky Way is barely conceivable for us humans. But it’s only a very tiny part of the entire Universe, which is made up of several hundred billion galaxies.
Our position in the Milky Way
Our Sun lies on the Orion arm of the Milky Way and orbits the centre of the galaxy at a distance of 25,000 to 28,000 light years. It takes 220 to 240 million years for the Sun to complete a single orbit around the central black hole Sagittarius A*– and that’s at the breath-taking orbital speed of around 800,000 km/h.
Our solar system
The solar system in which we live was formed around 4.5 billion years ago from a disc of swirling gas and dust. It consists of one sun and eight planets. Planets are large, round celestial bodies that orbit a star and do not emit their own light. They orbit on their own path alone, because their relatively large mass means that they attract all other heavenly bodies in their way. The Romans gave the planets their names, which they still have in many European languages today.
The Sun
Like all light-emitting stars, our Sun radiates energy. This energy originates from reactions inside the Sun, in which the hydrogen converts to helium in a process called nuclear fusion. These processes are the source of almost all the energy available on Earth.
For a long time, people were convinced that the Earth was the centre of the Universe. Astronomer and mathematician Nicolaus Copernicus rejected that idea in 1514. He was certain that the planets and therefore the Earth too were orbiting the Sun. A shocking idea! It wasn’t until the 17th century that this model gradually became accepted.
Mercury
Mercury completes an orbit of the Sun in just 88 days. That was why the Romans named it after the speedy messenger god, Mercury. The smallest planet in our solar system has an extremely thin atmosphere. For this reason its surface temperature varies between −173 degrees Celsius in the night and +427 degrees Celsius in the sunlight.
Venus
Viewed from Earth, no other “star” sparkles more brightly than Venus. It’s the first celestial object to become visible in the evening, and the last one to disappear in the morning. For this reason it’s also known as the Evening Star or Morning Star. But Venus doesn’t emit its own light either. It reflects the light of the Sun, like all the other planets.
Earth
What good luck that Earth is just the right distance away from the Sun. It’s only thanks to this that life was able to develop on Earth. Any nearer to the Sun would be too hot, and further away would be too cold. It’s only in this habitable zone that water can stay in a liquid state for any length of time. That’s a prerequisite for the development of life as we know it.
Mars
Mars is made of ferrous rock. Its orange colour is nothing other than rust! The largest volcano on Mars is over 20 kilometres high. The tallest mountain on Earth, Mount Everest, would look quite small beside it at 8848 metres. Several Mars robots have already conducted geological investigations on the planet.
Jupiter
Jupiter is by far the largest planet of our solar system. The giant gas planet has almost the same composition as the Sun – but it’s still too light to ignite and become a star in its own right. Jupiter has at least 79 moons.
Saturn
Saturn’s famous rings consist of fragments of ice and rock in different sizes. In total there are over 100,000 rings in a flat disc. Other planets have rings too, but they aren’t as clearly defined and therefore can’t be seen so well.
Uranus
The ice planet Uranus was only discovered by the German-British astronomer and musician Wilhelm Herschel in 1781. Uranus has at least 27 moons, many of which are named after characters in the works of William Shakespeare.
Neptune
Neptune is the only planet that cannot be seen with the naked eye from Earth. As a result it wasn’t discovered until 1846 by astronomer Johann Gottfried Galle. Before that the mathematician Urbain Le Verrier had calculated the existence and approximate position of this planet. So Galle knew what to look out for.
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