In extreme environments, where pressure, temperature, and density are high, atoms change the way they emit and absorb light. Electrons are stripped from nuclei, forming a plasma, and the ions emit X-rays when struck by free electrons. To assist astronomers in identifying atoms under these harsh conditions, the Center for Astrophysics | Harvard & Smithsonian maintains the AtomDB database of X-ray spectra. This catalog provides essential information for studying conditions in many astrophysical environments, including those near black holes, stars, and neutron stars.
A star cluster in the center of the Flame Nebula about 1,400 light years from Earth.
Credit: X-ray: NASA/CXC/PSU/K.Getman, E.Feigelson, M.Kuhn & the MYStIX team; Infrared:NASA/JPL-Caltech
A Resource for X-ray Astronomers
At high temperature and density, collisions strip electrons away from nuclei, creating a plasma of ions and free electrons. Further collisions in this plasma stimulate the emission of light, leading to complex spectra. AtomDB is designed to catalog these spectra with a particular focus on X-rays, based on laboratory experiments and theoretical calculations.
The database is useful for astronomers doing X-ray observations of extreme environments such as galaxy clusters and the material swirling around black holes or other compact gravitationally-powerful bodies. The spectra can also be used for astrophysical modeling of these systems, to provide the best detailed theories for how extreme environments behave. The HITRAN and HITEMP databases provide similar resources for molecular spectroscopy.