Comoving and proper distancesMeasurement of distance In standard cosmology, comoving distance and proper distance (or physical distance) are two closely related distance measures used by cosmologists to define distances between objects. Comoving distance factors out the expansion of the universe, giving a distance that does not change in time except due to local factors, such as the motion of a galaxy within a cluster.
DistanceDistance is a numerical or occasionally qualitative measurement of how far apart objects, points, people, or ideas are. In physics or everyday usage, distance may refer to a physical length or an estimation based on other criteria (e.g. "two counties over").
LuminosityLuminosity is an absolute measure of radiated electromagnetic energy per unit time, and is synonymous with the radiant power emitted by a light-emitting object. In astronomy, luminosity is the total amount of electromagnetic energy emitted per unit of time by a star, galaxy, or other luminous astronomical object. In SI units, luminosity is measured in joules per second, or watts. In astronomy, the luminosity of the Sun, L☉ is often used as a unit of luminosity.
Expansion of the universeThe expansion of the universe is the increase in distance between gravitationally unbound parts of the observable universe with time. It is an intrinsic expansion, so it does not mean that the universe expands into anything or that space exists outside it. To any observer in the universe, it appears that all but the nearest galaxies (which are bound to each other by gravity) move away at speeds that are proportional to their distance from the observer, on average.
QuasarActive galactic nucleus (AGN) containing a supermassive black holeArtist's image of the accretion disc in ULAS J1120+0641, a very distant quasar containing a supermassive black hole with a mass two billion times that of the SunThe Chandra X-ray image of PKS 1127-145, a quasar about 10 billion light-years from Earth. An X-ray jet extends at least a million light-years from the quasar. Image is 60 arcseconds on a side. RA 11h 30m 7.10s Dec −14° 49' 27" in Crater.
Euclidean distanceIn mathematics, the Euclidean distance between two points in a Euclidean space is the length of the line segment between them. It can be calculated from the Cartesian coordinates of the points using the Pythagorean theorem, and therefore is occasionally called the Pythagorean distance. These names come from the ancient Greek mathematiciansEuclid and Pythagoras.
Friedmann–Lemaître–Robertson–Walker metricMetric based on the exact solution of Einstein's field equations of general relativity Part of a series onPhysical cosmology Big BangUniverse Age of the universe Chronology of the universe Early universe InflationBaryogenesisNucleosynthesis Backgrounds Gravitational wave (GWB) Microwave (CMB)Neutrino (CNB) Expansion and future Hubble's lawRedshift Expansion of the universe FLRW metricFriedmann equations Lambda-CDM model Future of an expanding universe Ultimate fate of the universe Components and structure Components Dark energyDark matter PhotonsBaryons Structure Shape of the universe Galaxy filamentGalaxy formation Large quasar group Large-scale structure ReionizationStructure formation Experiments Black Hole Initiative (BHI) BOOMERanG Cosmic Background Explorer (COBE) Dark Energy Survey Planck space observatory Sloan Digital Sky Survey (SDSS) 2dF Galaxy Redshift Survey ("2dF") Wilkinson Microwave AnisotropyProbe (WMAP) Scientists Aaronson Alfvén Alpher Copernicus de Sitter Dicke Ehlers Einstein Ellis Friedmann Galileo Gamow Guth Hawking Hubble Huygens Kepler Lemaître Mather Newton Penrose Penzias Rubin Schmidt Smoot Suntzeff Sunyaev Tolman Wilson Zeldovich List of cosmologists Subject history Discovery of cosmic microwavebackground radiation History of the Big Bang theory Timeline of cosmological theories Category Astronomy portalvte The Friedmann–Lemaître–Robertson–Walker metric (FLRW; /ˈfriːdmən ləˈmɛtrə ...
RedshiftChange in wavelength of lightAbsorption lines in the visible spectrum of a supercluster of distant galaxies (right), as compared to absorption lines in the visible spectrum of the Sun (left). Arrows indicate redshift. Wavelength increases up towards the red and beyond (frequency decreases).
General relativityTheory of gravitation as curved spacetime Slow motion computer simulation of the black hole binary system GW150914, during 0.33 s of its final inspiral, merge, and ringdown. The star field behind the black holes is being heavily distorted and appears to rotate and move, due to extreme gravitational lensing, as spacetime itself is distorted and dragged around by the rotating black holes.
GalaxyA galaxy is a physical system of stars, planetary systems, stellar remnants, substellar objects, interstellar gas, dust, and dark matter bound together by gravity. The word is derived from the Greekgalaxias (γαλαξίας), meaning 'milky', a reference to the Milky Way galaxy that contains the Solar System.
Physical cosmologyBranch of physics that studies mathematical models of the universeArtist conception of the Big Bang cosmological model, the most widely accepted out of all in physical cosmology (neither time nor size to scale)
Cosmic microwave backgroundTrace radiation from the early universeTemperature map of the cosmic microwave background measured by the Planck spacecraft*As an Amazon Associate I earn from qualifying purchases.