![]() ![]() ^ Bringmann, Torsten Hofmann, Stefan (23 April 2007).The Astrophysical Journal Supplement Series. "Five-Year Wilkinson Microwave Anisotropy Probe (WMAP) Observations: Data Processing, Sky Maps, and Basic Results". ^ Kolb, Edward Turner, Michael (1994).Decoupling occurred abruptly when the rate of Compton scattering of photons Γ 0.0026 it is possible to rule out WIMPs of certain masses as reasonable dark matter candidates. During this time, electrons combined with protons to form hydrogen atoms, resulting in a sudden drop in free electron density. ![]() Photon decoupling occurred during the epoch known as the recombination. They reveal crucial clues about how the universe formed. ![]() They can still be detected today, although they now appear as radio waves, and form the cosmic microwave background ("CMB"). Because the neutral hydrogen that formed was transparent to light, those photons which were not captured by other hydrogen atoms were able, for the first time in the history of the universe, to travel long distances. Because direct recombinations to the ground state (lowest energy) of hydrogen are very inefficient, these hydrogen atoms generally form with the electrons in a high energy state, and the electrons quickly transition to their low energy state by emitting photons. During recombination, free electrons became bound to protons (hydrogen nuclei) to form neutral hydrogen atoms. Photon decoupling is closely related to recombination, which occurred about 378,000 years after the Big Bang (at a redshift of z = 1100), when the universe was a hot opaque ("foggy") plasma. The two verified instances of decoupling since the Big Bang which are most often discussed are photon decoupling and neutrino decoupling, as these led to the cosmic microwave background and cosmic neutrino background, respectively. This occurs as a result of the expansion of the universe, as their interaction rates decrease (and mean free paths increase) up to this critical point. In cosmology, decoupling refers to a period in the development of the universe when different types of particles fall out of thermal equilibrium with each other. ![]()
0 Comments
Leave a Reply. |
Details
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |