The sun

Introductory text to the sun

The sun The sun is one of about 200 billion stars in the Milky Way. As a central star, ie the center of a planetary system, the sun is orbited by eight planets: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune. Over 99% of the total mass of our solar system is attributable to the sun, which creates an enormous gravitational field, which ultimately also causes the planets to circle around the sun, not the sun around the planets.

Before the light of the sun hits the earth, 8 minutes and 20 seconds pass. This time takes the light to cover the distance between two celestial bodies (150,000,000 km). And that although light moves at about 300,000 kilometers per second. So when we see the sun or other stars in the sky, we are looking into the past, so to speak. Some stars in the night sky do not exist anymore. The light needs millions of years, depending on where the star is in orbit, before it can be seen here in the sky.

Not only planets revolve around themselves. The sun needs about 25 days at its equator for a complete revolution. At the poles, the required duration for one turn is even 36 days. In contrast to the earth, the sun is a plasma gas ball. Centrifugal forces are probably responsible for the 'speed surplus' at the solar equator.

Building the sun

Similar to the earth, the sun also consists of separable shells. Inside is the core. Here is the highest density (200 billion bar) and temperature (15 million ° C). The nuclear fusion of hydrogen to helium takes place mainly here. Every second, the sun loses four tons of mass, which corresponds to the amount of radiant energy released. Around the core lies the radiation and convection zone, through which the energy is directed towards the outside. It takes between 1 and 5 million years for the energy to ultimately radiate outward from the core. The photosphere forms the surface of the sun. At 6000 ° C, the surface is comparatively cool. In this sphere the sunspots can be observed. On it lies the chromosphere, a gas layer of hydrogen and helium. Solar flares can be observed in this sphere. The outermost atmosphere of the sun is the corona, which can only be observed during a solar eclipse. At high solar activity, the corona can reach over two sun radii. It consists of ionized plasma and, at two million ° C, is significantly hotter than the solar surface.

The sun as a universal life donor

Without the sun, life on earth would be impossible. According to the law of conservation of energy, energy can not be generated or destroyed but merely converted. The radiation energy of the sun hits the earth and thus is the starting point of all further energy conversion processes. Even a reduction in incident solar radiation by just a few percent can already cause a mass extinction on Earth, as the meteorite impact on the Yucatan Peninsula (Mexico) proves, which probably led to the extinction of the dinosaurs 65 million years ago. Because not the impact itself led to extinction. The collision of the meteorite with the earth carried tons of dust particles into the Earth's atmosphere, causing most of the sun's rays to be reflected back into the exosphere instead of falling onto the Earth's surface. This set in motion a chain reaction that caused the food chains to collapse. Less sunlight means an immediate drop in temperatures on Earth. Plants that depend on sunlight for photosynthesis grew slower or even died altogether. This also applies to the phytoplankton in the oceans. Plants and phytoplankton are indispensable as primary producers in the material cycle on earth. The animals that feed on autotrophic organisms are, in turn, food for other animals in the food chain. If only one link in the food chain disappears or if it is only available to a limited extent as a food source for the consumer group above, the food chain collapses from this point onwards.

The end of the solar system

The solar system is between 4.5 and 4.6 billion years old. At the latest in 7 billion years, when all the hydrogen in the Sun has been fused into helium, the lifetime of the solar system ends. The sun expands to almost three times its current radius ("Red Giant"). Mercury and Venus get into the vicinity of the sun. Both planets are destroyed as temperatures on Earth rise to well over 1000 ° C and destroy all life. Helium also burns in the following 100 million years or nuclear fusion of the helium atoms occurs. It creates carbon and oxygen. The temperature in the core of the sun is now over 100,000,000 ° C. Even if helium is completely used up, the sun has only the size of today's earth. It is referred to as a "white dwarf" that is enveloped in planetary nebulae. This mist, consisting of gases and dust, lights up due to the hot ambient temperature and is of relatively short duration. The temperatures are already not high enough to merge further elements by nuclear fusion. The white dwarf now cools down until it finally becomes the "black dwarf". So far, no black dwarfs could be detected in the universe. On the one hand, because the universe is not yet old enough for a star to reach this state, and on the other hand, if there are black dwarfs, they are barely discernible because they no longer radiate light.

The dangerous look in the sun

Solar Eclipse To imagine the enormous size of the Sun: Our blue planet is more than 100 times in the sun. The mass density of the sun is 300,000 times higher than the density of the earth. And as great as the sun is, it can be so dangerous for us. Because of the tremendous radiance, you should under no circumstances look directly into the sun. During a solar eclipse, many can not resist the temptation and thus attract irreparable eye injuries. Looking at the sun can quickly burn the cornea or damage the retina. With the telescope, a quick look into the sun is even more dangerous. Special eclipse glasses or sun filters provide a safe remedy here. By the way: normal sunglasses are not designed for the view in the direct sun!

Summary

The sun is a star in the Milky Way and the center of our solar system.

Eight planets orbit the sun: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune.

The structure of the Sun from inside to outside: core, radiation zone, convection zone, photosphere, chromosphere and corona.

The light needs just over eight minutes from the sun to the earth.

Inside the Sun hydrogen atoms are fused to helium. Part of the resulting energy is emitted into the cosmos.

At the latest in seven billion years, the sun collapses, destroying the planets close to the sun. In the end, the sun stays behind as a so-called black dwarf.