The standard model for an active galactic nucleus is based upon an accretion disc that forms around a supermassive black hole ( SMBH ) at the core region.

Simulations of the evolution of the Oort cloud from the beginnings of the Solar System to the present suggest that the cloud's mass peaked around 800 million years after formation, as the pace of accretion and collision slowed and depletion began to overtake supply.

The quasar is powered by an accretion disc around the black hole.

The matter accreting onto the black hole is unlikely to fall directly in, but will have some angular momentum around the black hole that will cause the matter to collect in an accretion disc.

In many cases, the inflowing gas forms an accretion disc around the accretor.

A stellar wind from the star provides material for an accretion disk around the X-ray source.

An accretion disc is a structure ( often a circumstellar disk ) formed by diffuse material in orbital motion around a central body.

Some of his significant achievements are his discovery, with Douglas Eardley, of a structural instability in orbitting disks of matter, called accretion disks, that form around massive condensed object such as black holes, with

The infalling matter, which is usually rich in hydrogen, forms in most cases an accretion disc around the white dwarf.

The expected spectrum of an accretion disc around a supermassive black hole peaks in the optical-ultraviolet waveband ; in addition, a corona of hot material forms above the accretion disc and can inverse-Compton scatter photons up to X-ray energies.

The brightest part of the system is the accretion disk around the compact object.

A black hole can sometimes be detected by the halo of bright gas and dust that forms around it as an accretion disc being pulled in by the black hole's gravity.

However, each part of the accretion disk has a different velocity relative to our line of sight, and the faster the gas is rotating around the black hole, the broader the line will be.

The star formation process naturally results in the appearance of accretion disks around young stellar objects.

With Igor Novikov and Don Page he developed the general relativistic theory of thin accretion disks around black holes, and using this theory he deduced that with a doubling of its mass by such accretion a black hole will be spun up to 0. 998 of the maximum spin allowed by general relativity, but never any farther ; this is probably the maximum black-hole spin allowed in Nature.

The calcite gradually accumulated ( by accretion ) around the fragments of shell in concentric layers, forming small balls ( of less than 0. 5 mm diameter ).

The scenarios invoked to explain this formation involve either star formation in a massive star cluster offset from the Galactic Center that would have migrated to its current location once formed, or star formation within a massive, compact gas accretion disk around the central black-hole.

* Bruno Rossi Prize in 1988 for his contributions to understanding cosmic X-ray sources, especially the structure of accretion disks around black holes, the X-ray spectra of compact objects, and the Mir-based discovery of hard X-ray emission from supernovae 1987A

Mass accretion rates for these objects are estimated to be around 10 < sup >− 4 </ sup > solar masses per year.

According to scientific consensus, the earth formed in orbit around the sun about 4. 5 billion years ago by accretion from a protoplanetary disk, and remained near its original orbit until the present.

Kenorland was formed around 2. 7 billion years ago ( 2. 7 Ga ) as a result of a series of accretion events and the formation of new continental crust ( Halla, 2005 ).

The accretion events are recorded in the greenstone belts of the Yilgarn Craton as metamorphosed basalt belts and granitic domes accreted around the high grade metamorphic core of the Western Gneiss Terrane, which includes elements of up to 3. 2 Ga in age and some older portions, for example the Narryer Gneiss Terrane.

However, the Emperor had netted an enormous accretion of power: Leopold I's son, Joseph, had been named King of the Romans ( 1690 ), and the Emperor's candidate for the Polish throne, August of Saxony, had carried the day over Louis XIV's candidate, the Prince of Conti.

A measure of the total mass accretion of meteoritic material by the Earth is obtained from analyses of deep-sea sediments and dust collected in remote regions ( Pettersson, 1960 ).

Matter falling onto a black hole can form an accretion disk heated by friction, forming some of the brightest objects in the universe.

Marta Weigle further developed and refined this typology to highlight nine themes, adding elements such as deus faber, a creation crafted by a deity, creation from the work of two creators working together or against each other, creation from sacrifice and creation from division / conjugation, accretion / conjunction, or secretion.

The universe was very violent in its early epochs, and galaxies grew quickly, evolving by accretion of smaller mass galaxies.

The observed state of gas within a cluster is determined by a combination of shock heating during accretion, radiative cooling, and thermal feedback triggered by that cooling.

During the 12th century, Arthur's character began to be marginalised by the accretion of " Arthurian " side-stories such as that of Tristan and Iseult.

It is caused by the accretion of hydrogen on to the surface of the star, which ignites and starts nuclear fusion in a runaway manner.

Still, about half of the resulting protostellar objects will be left surrounded by circumstellar disks, many of which form accretion disks.

The orchestra grew by accretion throughout the 18th and 19th centuries, but changed very little in composition during the course of the 20th century.

Quasars are believed to be powered by accretion of material into supermassive black holes in the nuclei of distant galaxies, making these luminous versions of the general class of objects known as active galaxies.

However, when accretion disc energy-production mechanisms were successfully modeled in the 1970s, the argument that quasars were too luminous became moot and today the cosmological distance of quasars is accepted by almost all researchers.

For historic material established text typefaces are frequently chosen according to a scheme of historical genre acquired by a long process of accretion, with considerable overlap between historical periods.

The calcareous – probably aragonitic – shells have a cover ( operculum ) and two curved supports known as helens, all of which grew by marginal accretion.

There is mounting evidence that at least some massive protostars are indeed surrounded by accretion disks.

Of these, perhaps the most prominent is the theory of competitive accretion, which suggests that massive protostars are " seeded " by low-mass protostars which compete with other protostars to draw in matter from the entire parent molecular cloud, instead of simply from a small local region.

The accretion of continents about 3. 5 billion years ago added plate tectonics, constantly rearranging the continents and also shaping long-term climate evolution by allowing the transfer of carbon dioxide to large land-based carbonate storages.

Other mechanisms that have been suggested at various times for the Moon's origin are that the Moon was spun off from the Earth's molten surface by centrifugal force, that it was formed elsewhere and subsequently, was captured by the Earth's gravitational field, or that the Moon formed at the same time and place as the Earth from the same accretion disk.

It formed at ~ 1. 0 Ga by accretion and collision of fragments produced by breakup of the older supercontinent, Columbia, which was assembled by global-scale 2. 0-1. 8 Ga collisional events.