The Sun: The Star from Which We Live

Abstract

Without the sun, no light, no heat, no life on Earth. The earth, if it existed at all, would be a dead dark planet covered with ice. The importance of the sun for life on earth was recognized by all peoples, and in many religions the sun was worshipped as a deity. In modern astrophysics, there are two particular reasons to look more closely at the study of our nearest star. First, the Sun is the only star where we can observe a wide variety of surface details such as spots, prominences, eruptions, flares, and so on. Even with the largest telescope in the world, stars can only be seen as pointlike spots. So the nearest star is the Sun 150,000,000 km away, Proxima Centauri is more than 300,000 times that distance. Second, we know that the Sun has a major impact on Earth and near-Earth space. During strong solar storms, satellites can become unstable, radio communications are disrupted, etc. In order to minimize the damage, we want to predict space weather, which is mainly influenced by the sun. In this chapter you will learn about

• the sun as the next star,

• why the sun shines,

• what sunspots are,

• whether the sun is shining constantly,

• how solar activity threatens our high-tech society.