Astronomy: Large-Scale Structure

Wikimedia Commons, CC BY-SA

Commentary

Source: Wikipedia (CC BY-SA)

Large-Scale Structure The observable universe is a spherical region of the universe consisting of all matter that ca n be observed from Earth; the electromagnetic radiation from these astronomical objects has had time to reach the Solar System and Earth since the beginning of the cosmological expansion. The radius of this region is about 14.26 gigaparsecs (46.5 billion light-years or 4.40×1026 m). The word observable in this sense does not refer to the capability of modern technology to detect light or other information from an object, or whether there is anything to be detected.

Commentary

Source: Internal

Why Large-Scale Structure matters: Cosmology addresses the deepest questions we can ask: where did the universe come from, what is it made of, and what will happen to it in the future? It refers to the physical limit created by the speed of light itself. No signal can travel faster than light and the universe has only existed for about 14 billion years. Objects which emit lig ht but which exist too far away for that light to have reached Earth are beyond the particle horizon, outside the observable universe. Every location in the universe has its own observable universe, which may or may not overlap with the one centered on Earth. According to calculations, the current comoving distance to particles from which the cosmic microwave background radiation (CMBR) was emitted, which represents the radius of the visible universe, is about 14.0 billion parsecs (about 45.7 billion light-years). The comoving distance to the edge of the observable universe is about 14.3 billion parsecs (about 46.6 billion light-years), about 2% larger. The radius of the observable universe is therefore estimated to be about 46.5 billion light-years. Using the critical density and the diameter of the observable universe, the total mass of ordinary matter in the universe can be calculated to be about 1.5×1053 kg. In November 2018, astronomers reported that extragalactic background light (EBL) amounted to 4×1084 photons. As the universe's expansion is accelerating, all currently observable objects, outside the local supercluster, will eventually appear to freeze in time, while emitting progressively redder and fainter light. For instance, objects with the current redshift z from 5 to 10 will only be observable up to an age of 4–6 billion years. In addition, light emitted by objects currently situated beyond a certain comoving distance (currently about 19 gigaparsecs (62 Gly)) will never reach Earth.

Commentary

Source: Internal

Deep dive: Large-Scale Structure No signal can travel faster than light and the universe has only existed for about 14 billion years. Objects which emit light but which exist too far away for that light to have reached Earth are beyond the particle horizon, outside the observable universe. Every location in the universe has its own observable univer se, which may or may not overlap with the one centered on Earth. According to calculations, the current comoving distance to particles from which the cosmic microwave background radiation (CMBR) was emitted, which represents the radius of the visible universe, is about 14.0 billion parsecs (about 45.7 billion light-years). The comoving distance to the edge of the observable universe is about 14.3 billion parsecs (about 46.6 billion light-years), about 2% larger. The radius of the observable universe is therefore estimated to be about 46.5 billion light-years. Using the critical density and the diameter of the observable universe, the total mass of ordinary matter in the universe can be calculated to be about 1.5×1053 kg. In November 2018, astronomers reported that extragalactic background light (EBL) amounted to 4×1084 photons. As the universe's expansion is accelerating, all currently observable objects, outside the local supercluster, will eventually appear to freeze in time, while emitting progressively redder and fainter light. For instance, objects with the current redshift z from 5 to 10 will only be observable up to an age of 4–6 billion years. In addition, light emitted by objects currently situated beyond a certain comoving distance (currently about 19 gigaparsecs (62 Gly)) will never reach Earth. Source: https://en.wikipedia.org/wiki/Observable_universe (Wikipedia, CC BY-SA)