advertisement
WikiVisually
Infinite photos and videos for every Wiki article · Find something interesting to watch in seconds
Great Cities Animals Celebrities Richest US Counties Tallest Buildings Supercars History by Country Recovered Treasures Kings of France World Banknotes Sports British Monarchs Famous Castles Best Campuses Crown Jewels Largest Palaces Rare Coins Orders and Medals Presidents Great Artists Largest Empires Great Museums Wonders of Nature Countries of the World Ancient Marvels Wars and Battles
more top lists
History
Accretion (astrophysics)
Videos
Page
In astrophysics, accretion is the accumulation of particles into a massive object by gravitationally attracting more matter, typically gaseous matter, into an accretion disk. Most astronomical objects, such as galaxies, stars, and planets, are formed by accretion processes.
ALMA image of HL Tauri, a protoplanetary disk
ALMA image of HL Tauri, a protoplanetary disk
The visible-light (left) and infrared (right) views of the Trifid Nebula, a giant star-forming cloud of gas and dust located 5,400 light-years (1,700
The visible-light (left) and infrared (right) views of the Trifid Nebula, a giant star-forming cloud of gas and dust located 5,400 light-years (1,700 pc) away in the constellation Sagittarius
Infrared image of the molecular outflow from an otherwise hidden newborn star HH 46/47
Infrared image of the molecular outflow from an otherwise hidden newborn star HH 46/47
When the lower-mass star in a binary system enters an expansion phase, its outer atmosphere may fall onto the compact star, forming an accretion disk
When the lower-mass star in a binary system enters an expansion phase, its outer atmosphere may fall onto the compact star, forming an accretion disk
Accretion disk
Videos
Page
An accretion disk is a structure 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. Gravitational and frictional forces compress and raise the temperature of the material, causing the emission of electromagnetic radiation. The frequency range of that radiation depends on the central object's mass. Accretion disks of young stars and protostars radiate in the infrared; those around neutron stars and black holes in the X-ray part of the spectrum. The study of oscillation modes in accretion disks is referred to as diskoseismology.
The hot accretion disc of a black hole, showing the relativistic effects imposed on light when it is emitted in regions subject to extreme gravitation
The hot accretion disc of a black hole, showing the relativistic effects imposed on light when it is emitted in regions subject to extreme gravitation. This image is the result of NASA simulations and shows a view from outside the horizon of a Schwarzschild black hole.
Artist's view of a star with accretion disk
Artist's view of a star with accretion disk
Artist's conception of a black hole drawing matter from a nearby star, forming an accretion disk
Artist's conception of a black hole drawing matter from a nearby star, forming an accretion disk
HH-30, a Herbig–Haro object surrounded by an accretion disk
HH-30, a Herbig–Haro object surrounded by an accretion disk