The history of the development of the universe
It began in the first minutes of the Big Bang, when the atomic nuclei of the elements hydrogen, helium and lithium were already forming. The universe had to cool down for a further 380,000 years before electrons could be bound to these nuclei and the first elements formed. All other elements in the periodic table originated in stars, except for the heaviest elements, which were synthesized artificially in research centers such as GSI. Stars exploit the property that the fusion of two lighter nuclei to form a heavier nucleus can generate energy, which the star uses to exist in equilibrium for millions to billions of years while also radiating large amounts of energy. At some point, a star has used up its nuclear energy reservoir, and if it is massive enough, it will meet a dramatic fate: it explodes as a supernova, hurling the elements it has incubated inside into space, where they were used to form life on a small planet around a fairly inconspicuous star.
However, supernovae only produce elements up to the iron-nickel mass range. To make the heavier elements, nature has another trick: Through the progressive accumulation of neutrons on seed nuclei, the mass number of the nuclei can be successively increased, whereby this sequence is interrupted by decays in which a neutron transforms into a proton, thus advancing one step in the periodic table. The problem with this trick, however, is that there are actually no more free neutrons after the Big Bang and the star has to produce them on site. This can happen quite peacefully during special periods in the life of stars that are somewhat more massive than the sun, or in spectacular events such as the fusion of two neutron stars.
The sun is a universal star, but not for us, as we would not exist without it. Today we know a great deal about the sun and have managed to look deep inside the sun using two different methods to test our theoretical ideas about stars, with spectacular success.
The lecture will first discuss the cosmic alchemy of the first almost 14 billion years of the universe. But at the end, Karlheinz Langanke will venture an outlook on the next billion years and beyond.
Lecture is in German language.