Storm in space

A solar storm raced towards Earth on Saturday at a speed of 800 kilometres per second. So far, there has been no significant damage to the technology in space. But the danger has not yet been averted: A solar storm can cause the Earth’s magnetic field to oscillate for days.

Last Thursday, a solar eruption ejected a stream of particles towards Earth. Experts call this a “coronal mass ejection”. On Saturday evening, its charged particles reached the Earth around 9.30 pm and collided with its magnetic field. This could have severely disrupted satellite and navigation technology. Fortunately, this was not the case.

From the experts’ point of view, the solar storm could have been much more violent. Only in the course of Saturday did it become apparent that the charged particles were not racing through space as fast as first assumed. The storm only reached a magnitude of one on a scale of five. However, it is too early to sound the all-clear, because the storm in space is not yet over. The solar storm is not directly dangerous for humans. However, navigation, electricity and mobile phone networks could be disrupted for several days.

Auroras are another “side effect” of the solar storm. As its electrically charged particles flow along the Earth’s magnetic field towards the poles, they cause a coloured glow in the night sky in the polar regions. If a solar storm is particularly strong, the colourful auroras can also be seen over Germany. So we should keep our eyes open tonight!

The Super Solar Storms

Solar storms have been observed for more than 200 years. The most powerful solar storm to date is considered to be the one in September 1859: at that time, auroras were even observed in Italy, Cuba and Hawaii. In Northern Europe and North America, high voltage current shot through telegraph lines until sparks flew. Many lines were damaged and the worldwide telegraph network was severely affected. Solar storms also caused damage and excitement in later years: in 1989, for example, the power grid in Canada collapsed after such a natural event. In 2003, a solar storm led to power outages in Sweden, the collapse of European air traffic radar and caused more than 60 flights to be postponed in the USA. Last but not least, the research satellite “ADEOS 2” was lost.

Earth magnet

We don’t notice it, but the compass needle shows us clearly: the earth is a huge magnet. It has two magnetic poles, a north pole and a south pole. And like all magnets, the earth is surrounded by a magnetic field: the earth’s magnetic field.

In the area of its magnetic field, a magnet exerts force on other magnets, for example on a compass needle. The effect of a magnet can also be made visible by fine iron filings: they arrange themselves around the magnet and point in the direction of its two poles. A line-like pattern is created that indicates the magnetic forces. The lines of this magnetic field are the so-called field lines.

The earth’s magnetic field also has such field lines. They emerge from the earth near the south pole, run outside the earth to the north pole and disappear into the earth again there. They are thus arranged as if a huge bar magnet were running through the middle of the earth.

The south pole of this imaginary bar magnet points approximately to the geographical north pole, its north pole to the geographical south pole. What sounds confusing at first has a simple explanation: the north and south poles attract each other. That is why the north pole of the compass needle points to the magnetic south pole of the earth, and the south pole on the needle points to the magnetic north pole.

However, the Earth’s magnetic field is not only used for orientation on this planet. Together with the atmosphere, it also protects us from threats from space. One of these threats is a charged particle stream that the sun constantly emits in all directions. This so-called solar wind is deflected by the Earth’s magnetic field. Like a capsule, the Earth’s magnetic field deflects the charged particles so that they fly past the Earth and can no longer be dangerous to us.

Aurora Borealis

Polar lights shine red, green or blue in the night sky. As their name suggests, they usually appear in the polar regions: in the northern hemisphere, mainly in the north of Scandinavia, Scotland and Siberia, in Greenland, Canada and Alaska. The greater the distance from the pole, the rarer the auroras. They appear most frequently in the winter months, when it is dark for a long time. Then auroras can be seen on almost every clear night.

The colourful light effects in the sky were a mystery to man for a long time. Today, their secret has been revealed: the sun is responsible for the glow of the aurora borealis. For it not only emits light and heat, but also hurls gigantic masses of matter into space. This so-called solar wind consists mainly of electrically charged particles that race through space at a speed of more than 300 kilometres per second. After only about three days, these energy-charged particles reach the earth.

Fortunately, we are protected from the impact of these particles by the atmosphere and the Earth’s magnetic field. So they cannot reach the Earth’s surface and become dangerous to us. Nevertheless, the solar wind affects the Earth by deforming its magnetic field: On the side facing the sun, it is compressed; on the side facing away from the sun, it protrudes further into space.

Where the solar wind meets the Earth’s magnetic field – at an altitude of over 100 kilometres – a strong electrical voltage builds up. Part of this voltage is discharged as the electrons flow along the field lines of the magnetic field towards Earth. They come closest to our planet at the poles. When they collide there with the oxygen and nitrogen atoms of the atmosphere, these emit light – similar to the gas in a fluorescent tube. Depending on the energy of the impact, they glow in different colours. We see the result as colourful auroras.

At intervals of about eleven years, the sun is particularly active and throws more particles into space than usual. Then the solar wind can become a solar storm. Sometimes it is so strong that auroras can also be seen in areas outside the polar region. However, such a solar storm not only produces the pretty aurora borealis, but can also disrupt satellite technology, power lines, radio and navigation. In 1989, for example, the electricity in Canada was cut off for days.

What is a star?

When it is particularly dark at night and the sky is clear, we see thousands of stars twinkling as tiny points of light above our heads. But why do the stars shine? What are stars anyway?

Stars are simply balls of gas. But inside them it is unimaginably hot, many millions of degrees Celsius. Because of the intense heat, the gas glows and shines – like a light bulb, only much brighter. The light from the stars is so strong that we can see it from Earth, even though the stars are many trillions of kilometres away.

Stars appear to us like tiny points of light – but that is only because of the great distance: in reality, stars are huge. The smallest ones have about ten times the diameter of the Earth, giant stars can be a hundred thousand times larger!

However, there is one star that is very close to us compared to all the others: the sun. It already appears to us as a bright disc in the sky. But even this impression is deceptive: the diameter of the sun is about one hundred times that of the earth. We see and feel its power every day, because it gives the earth light and warmth – like a big campfire where we sit in the cold universe.

However, a star does not burn wood. It consists mainly of hydrogen gas and draws its energy from the hydrogen atomic nuclei. So a star slowly burns itself, so to speak. When at some point the fuel supplies are exhausted, it goes dark and collapses or explodes. Our sun will also end up like that one day. But because stars are so big, the fuel lasts for a long time. Our sun, for example, will shine for about five billion years.