The Sun

What is the Sun ?

The Sun is our nearest star and is an important source of heat and light for our planet. It is four and a half billion years old and will probably continue burning for another 5 billion years. At the end of its lifetime the Sun will become bigger and cooler till it will die.

The distance between the Earth and the Sun is around 150 million kilometres. If you were travelling by car, you would need around 1,5 million hours or 170 years of travel time. 

Our Sun is an average sized star, a yellow dwarf, and there are many much bigger and also smaller stars. It is 1 400 000 kilometers in diameter, which makes it 110 times wider than the Earth. The Sun weighs 330 000 times more than the Earth. 

How does the Sun affect the Earth?

Everyone loves it when the weather is nice and warm, which is all thanks to our Sun. We can sunbathe, play outside,... On the other hand, activity on the Sun creates a type of weather called space weather. It can affect our Earth and the rest of the solar system. In general, there is always a stream of gas and particles charged with electricity coming from the corona, known as the solar wind. The magnetic field of the Earth protects us from the solar wind and we can see its collision with the magnetic field at both poles, known as the beautiful auroras. But sometimes the solar wind becomes more aggressive, when it carries solar storms, often produced by powerful solar flares. These storms can damage satellites used for communication and navigation (aviation, GPS, ...), they can disrupt power grids and also can be dangerous for astronauts in space.

Solar flares happen suddenly, in areas around the sunspots, and scientists try to predict when solar storms will occur and how strong they will be. If you want to know what the weather is like in space, you can check the space weather forecast.

Does the Sun always look the same?

The Sun is composed of extremely hot gas (called plasma) and has no solid surface.

When we look at the Sun, we see a yellow -white ball. We see the photosphere, the inner part of the Sun's atmosphere. On the photosphere, we can sometimes see dark spots, known as sunspots. The more sunspots, the higher the activity is on the Sun. Around the photosphere, there is another layer called chromosphere. To see this part of the sun, we need special cameras with particular filters. This layer is hotter than the photosphere.

The hottest layer is situated around the chromosphere and we call it the corona. We can see the corona during a solar eclipse or with special cameras.

The Sun continuously looses some of its material and this stream, called solar wind, moves outward passing the planets, to the outer edges of our solar system.

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Do we know everything about the Sun?

Scientists have already discovered a lot about our beautiful Sun, but there are still lots of questions. They can only see the Sun from the Earth, only one side at once and only from far away. Solar scientists want to see the Sun's poles, they want to see the Sun from nearby, they want to fly through a solar storm, and they want to improve their predictions of space weather.

Therefore ESA, together with many scientists and engineers around Europe, have build Solar Orbiter. This satellite will fly close to the Sun and will look at the poles of the Sun from above. It will also allow the scientists to look at the Earth side of the Sun and the back side at the same time. Scientists hope to collect more data to understand our Sun better. 

Image Courtesy: ESA

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