Accretion diskAn accretion disk is a structure (often a circumstellar disk) formed by diffuse material in orbital motion around a massive central body. The central body is most frequently a star. Friction, uneven irradiance, magnetohydrodynamic effects, and other forces induce instabilities causing orbiting material in the disk to spiral inward toward the central body.
Supermassive black holeA supermassive black hole (SMBH or sometimes SBH) is the largest type of black hole, with its mass being on the order of hundreds of thousands, or millions to billions, of times the mass of the Sun (M☉). Black holes are a class of astronomical objects that have undergone gravitational collapse, leaving behind spheroidal regions of space that nothing, not even light, can escape.
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.Active galactic nucleusAn active galactic nucleus (AGN) is a compact region at the center of a galaxy that emits a significant amount of energy across the electromagnetic spectrum, with characteristics indicating that this luminosity is not produced by the stars. Such excess, non-stellar emissions have been observed in the radio, microwave, infrared, optical, ultra-violet, X-ray, and gamma ray wavebands. A galaxy hosting an AGN is called an active galaxy.
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).
Accretion (astrophysics)In astrophysics, accretion is the accumulation of matter into a massive object by gravitationally attracting more matter. If the matter is gaseous the result is an accretion disc. Accretion of solid matter such as dust will form larger solid objects. Most astronomical objects, such as galaxies, stars, and planets, are formed by accretion processes.
EnergyPhysical quantityEnergy (from Ancient Greek ἐνέργεια (enérgeia) 'activity') is the quantitativeproperty that is transferred to a body or to a physical system, recognizable in the capacity to do work and in the form of heat and light. Energy is a conserved quantity—the law of conservation of energy states that energy can be converted in form, but not created or destroyed. The unit of measurement for energy in the International System of Units (SI) is the joule (J).
Milky WayGalaxy containing the Solar SystemArtist's impression of the structure of the Milky Way based on data from the European Space Agency's Gaia telescope, including the location of the spiral arms, bar, and bulgeThe Milky Way or Milky Way Galaxy, or simply the Galaxy, is the galaxy that includes the Solar System, with the name describing the galaxy's appearance from Earth: a hazy band of light seen in the night sky formed from stars in other arms of the galaxy, which are so far away that they cannot be individually distinguished by the naked eye.
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.
Electromagnetic radiationPhysical model of propagating energyA linearly polarized electromagnetic wave going in the z-axis, with E denoting the electric field and perpendicular B denoting magnetic fieldIn physics, electromagnetic radiation (EMR) or an electromagnetic wave (EMW) is a self-propagating wave of the electromagnetic field that carries momentum and radiant energy through space.
Radiant energyIn physics, and in particular as measured by radiometry, radiant energy is the energy of electromagnetic and gravitational radiation. As energy, its SI unit is the joule (J). The quantity of radiant energy may be calculated by integratingradiant flux (or power) with respect to time. The symbol Qe is often used throughout literature to denote radiant energy ("e" for "energetic", to avoid confusion with photometric quantities).
Solar massThe solar mass (M☉) is a frequently used unit of mass in astronomy, equal to approximately 2×10 kg. It is approximately equal to the mass of the Sun. It is often used to indicate the masses of other stars, as well as stellar clusters, nebulae, galaxies and black holes.*As an Amazon Associate I earn from qualifying purchases.