Boson x steam stage edit12/29/2022 ![]() ![]() ![]() The earliest generations of stars have not yet been observed astronomically. This period is known as the cosmic Dark Ages.Īt some point around 200 to 500 million years, the earliest generations of stars and galaxies form (exact timings are still being researched), and early large structures gradually emerge, drawn to the foam-like dark matter filaments which have already begun to draw together throughout the universe. The decoupled photons would have filled the universe with a brilliant pale orange glow at first, gradually redshifting to non-visible wavelengths after about 3 million years, leaving it without visible light. The only photons (electromagnetic radiation, or "light") in the universe were those released during decoupling (visible today as the cosmic microwave background) and 21 cm radio emissions occasionally emitted by hydrogen atoms. After recombination and decoupling, the universe was transparent but the clouds of hydrogen only collapsed very slowly to form stars and galaxies, so there were no new sources of light. This period measures from 370,000 years until about 1 billion years. The Dark Ages and large-scale structure emergence This is the oldest direct observation we currently have of the universe. The newly formed atoms-mainly hydrogen and helium with traces of lithium-quickly reach their lowest energy state ( ground state) by releasing photons (" photon decoupling"), and these photons can still be detected today as the cosmic microwave background (CMB). (Much later, hydrogen and helium hydride react to form molecular hydrogen (H2) the fuel needed for the first stars.) At about 370,000 years, neutral hydrogen atoms finish forming ("recombination"), and as a result the universe also became transparent for the first time. At around 100,000 years, after the neutral helium atoms form, helium hydride is the first molecule. At around 47,000 years, as the universe cools, its behavior begins to be dominated by matter rather than radiation. The recombination epoch begins at around 18,000 years, as electrons are combining with helium nuclei to form He + Composite subatomic particles emerge-including protons and neutrons-and from about 2 minutes, conditions are suitable for nucleosynthesis: around 25% of the protons and all the neutrons fuse into heavier elements, initially deuterium which itself quickly fuses into mainly helium-4.īy 20 minutes, the universe is no longer hot enough for nuclear fusion, but far too hot for neutral atoms to exist or photons to travel far. If primordial black holes exist, they are also formed at about one second of cosmic time. These particles include almost equal amounts of matter and antimatter, so most of it quickly annihilates, leaving a small excess of matter in the universe.Īt about one second, neutrinos decouple these neutrinos form the cosmic neutrino background (CνB). Initially, various kinds of subatomic particles are formed in stages. The earlier parts are beyond the grasp of practical experiments in particle physics but can be explored through other means. Different stages of the very early universe are understood to different extents. Tiny ripples in the universe at this stage are believed to be the basis of large-scale structures that formed much later. It includes the Planck epoch, during which currently established laws of physics may not apply the emergence in stages of the four known fundamental interactions or forces-first gravitation, and later the electromagnetic, weak and strong interactions and the expansion of space itself and supercooling of the still immensely hot universe due to cosmic inflation. The first picosecond (10 −12) of cosmic time. It is generally considered meaningless or unclear whether time existed before this chronology: Outline Chronology in five stages ĭiagram of evolution of the (observable part) of the universe from the Big Bang (left), the CMB-reference afterglow, to the present.įor the purposes of this summary, it is convenient to divide the chronology of the universe since it originated, into five parts. 5.4 Galaxies, clusters and superclusters.5.2 Earliest structures and stars emerge.5.1.1 Oldest observations of stars and galaxies.5 The Dark Ages and large-scale structure emergence.4.11 Recombination, photon decoupling, and the cosmic microwave background (CMB).4.6 Possible formation of primordial black holes.4.5 Neutrino decoupling and cosmic neutrino background (CνB). ![]() 4.1 Electroweak epoch and early thermalization.3.5 Supersymmetry breaking (speculative).3.4 Inflationary epoch and the rapid expansion of space.1.1.3 The Dark Ages and large-scale structure emergence. ![]()
0 Comments
Leave a Reply.AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |