Spectral synthesis code to simulate conditions in interstellar matter
Most of the quantitative information we have about the cosmos comes from spectroscopy. In many cases the light we analyze was produced by atoms in the first generations of stars and galaxies. The spectra are produced by dilute gas where such properties as the gas kinetic temperature, chemical state, level of ionization, and level populations, are determined by a host of microphysical processes rather than by a single temperature. Analytical solutions are seldom possible and computer solutions are needed to understand their physical properties. Numerical simulations make it possible to understand complex physical environments starting from first principles. Cloudy is designed to do exactly this.