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Five solar flares were created at the end of June within just five days. In the picture they are recognizable as particularly bright spots, taken in a wavelength from the extreme ultraviolet range. On Earth, the eruptions called out northern lights. (Photo: Solar Dynamics Observatory, NASA)

Ganze fünf Sonneneruptionen entstanden Ende Juni innerhalb von nur fünf Tagen. Auf dem Bild sind sie als besonders helle Flecken erkennbar, aufgenommen in einer Wellenlänge aus dem extrem-ultravioletten Bereich. Auf der Erde riefen die Eruptionen Nordlichter hervor. (Foto: Solar Dynamics Observatory, NASA)

Five solar flares were created at the end of June within just five days. In the picture they are recognizable as particularly bright spots, taken in a wavelength from the extreme ultraviolet range. On Earth, the eruptions called out northern lights. (Photo: Solar Dynamics Observatory, NASA)

The sun is completely made of gas and does not have a solid core. Nevertheless, the star has something like a surface on which all sorts of activities can be seen. The NASA satellite SDO - short for "Solar Dynamics Observatory" - regularly makes impressive pictures of it.

The mission began more than five years ago. On January 11, 2010, NASA sent its "Solar Dynamics Observatory" (SDO) into orbit from Cape Canaveral. At an altitude of about 35, 800 kilometers, the spacecraft has been orbiting the earth ever since and is filming the sun from there. At a speed of 130 megabits per second, the probe constantly sends images to the base station on the ground.

The goal of the mission is to find out more about the changes in solar activity. Then conversely, changes could be better predicted, the researchers hope. This is interesting because the fluctuations in solar activity affect the "space weather", which also affects the conditions on Earth. Northern lights, for example, are a beautiful result of solar flares. On the other hand, less damaging consequences are damage to power grids, transformers or electrical equipment caused by induced fields on the earth's surface. Large power lines act like antennas and disrupt the power supply over a large area.

The magnetic field of the sun

SDO measures different quantities, including the strength of the solar magnetic field, which is responsible for the varying activity of the sun. The magnetic field affects the number and size of sunspots - dark spots on the sun's surface where the magnetic field is stronger and the temperature is lower. Also affected by the magnetic field are solar flares and coronal mass ejections.

However, the strength of the magnetic field changes with cyclic regularity. Eleven years each lie between its lowest and its greatest strength, with the magnetic north and south poles also exchanging places in the interval of eleven years. display

The sun itself consists of 92.1 percent hydrogen and 7.8 percent helium. At its core, the temperature is around 15 million degrees Celsius. From there, energy comes out in the form of radiation, traverses several layers of the sun, and finally ends up in the photosphere, the visible surface of the sun. There still prevail 55, 000 degrees Celsius. From the photosphere, a large part of the solar radiation reaches out into free space - and thus also to the earth.

.De science.de - Henrike Wiemker
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