Cosmic Density-Temperature-Composition Diagrams

The location of baryonic matter in the density-temperature diagram
Almost all baryonic matter in the universe has a well defined temperature and density -- and therefore has a location in this diagram. As with the other diagrams, the axes are exponential, spanning 50 decades of density, from a millionth of closure density to super-nuclear density. Likewise the temperature axis spans 10 decades, from absolute zero to temperatures hotter than the cores of stars. Recall, temperature is essentially the energy per particle (atom, electron, proton, photon, or whatever), and so an equivalent scale in eV is labelled. It is important to recognize how different regions in the diagram do or don't allow certain processes to occur. For example, typical molecular bonds require a few tenths eV to break -- hence complex molecules only survive below around 100 C (400 K). On the other hand, chemical reactions only proceed with speed at temperatures above 200K (roughly liquid nitrogen) and at densities which allow atoms to touch, but not be so compressed that the bonds are broken. Hence one only expects complex chemistry (eg life) to exist when matter is located within the tiny green dashed region. Simple molecules with strong bonds can survive up to a few thousand degrees, above which one finds only single atoms. Since outermost electrons are bound to nuclei with an energy of 1-few eV, then above 10,000K the atoms begin to become ionized. This state is only completed near a million K as the innermost electrons are lost. In order for protons to stick, they need to overcome their Coulomb repulsion, which they only begin to do above about 10 million degrees, with heavier nuclei beginning to fuse above 100 million degrees. However, above a few billion degrees, the strong inter-nuclear force -- which has ~1MeV of strength -- begins to break, and nuclei can no longer survive -- one find nuclear disintegration. Hence, atomic nuclei can only be created somewhere within the larger green dashed region. On this diagram, stars occupy the large tilted oval, with very tenuous outer atmospheres, but significantly denser and hotter cores. Notice how the upper portion which includes stellar cores falls nicely withing the area where nuclei can be formed. Indeed the radial , T trend in the sun is shown as a continuous curve within the "star region". In the star's life, heavy elements made in the core are dredged up to the surface and then blown off into space where they join the ISM. To be completed....
Evolution of, and current day, cosmic composition
commentary to be done.
Animated power point slides of these diagrams can be found [here]. With successive clicks, the diagram is built up roughly following the descriptions given above. Figures made for "Designing Matter" Lectures, (by me).