accretion


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accretion

1. Botany the growing together of normally separate plant or animal parts
2. Pathol
a. abnormal union or growing together of parts; adhesion
b. a mass of foreign matter collected in a cavity
3. Law an increase in the share of a beneficiary in an estate, as when a co-beneficiary fails to take his share
4. Astronomy the process in which matter under the influence of gravity is attracted to and increases the mass of a celestial body. The matter usually forms an accretion disc around the accreting object
5. Geology the process in which a continent is enlarged by the tectonic movement and deformation of the earth's crust

accretion

(aggregation) The increase in mass of a body by the addition of smaller bodies that collide and stick to it. The relative velocity of any two colliding bodies must be low enough for them to coalesce on impact rather than fly apart. Once a large enough body forms, its gravitational attraction accelerates the accretion process. Accreting objects in the Universe are numerous and diverse. They include protoplanets, protostars, black holes, and X-ray binaries. The accretion process is thought to occur generally in the form of a disk. Accretion is now assumed to have had an important role in the formation of the planets from swarms of dust grains. In the outer Solar System the grains were like dirty snowflakes and thus accretion was accelerated. See Solar System, origin.

accretion

[ə′krē·shən]
(astronomy)
A process in which a star gathers molecules of interstellar gas to itself by gravitational attraction.
(civil engineering)
Artificial buildup of land due to the construction of a groin, breakwater, dam, or beach fill.
(geology)
Gradual buildup of land on a shore due to wave action, tides, currents, airborne material, or alluvial deposits.
The process whereby stones or other inorganic masses add to their bulk by adding particles to their surfaces. Also known as aggradation.
(meteorology)
The growth of a precipitation particle by the collision of a frozen particle (ice crystal or snowflake) with a supercooled liquid droplet which freezes upon contact.
References in periodicals archive ?
If the system is observed from a vertical direction, it's clear that the central part of the accretion disk emits intense X-rays.
They found that only two types of accretion models, both of which involve the most strongly interacting binaries, could create these jetted pre-planetary nebulae.
2 has single spectral lines and therefore it was a surprise when our photometry during a superoutburst revealed shallow eclipses which we interpreted as grazing occultations of the edge of the accretion disc.
They cover mass and spin evolution of super-massive black holes, accretion and outflows, jets, news from the gamma-ray sky, feedback from AGN, and the radio-loud/radio-quiet dichotomy.
The rapid prototyping by material accretion permits to eliminate the aberration which consists for an engineer to conceive an object in three dimensions, to represent it in two dimensions, and then, in workshop, to interpret this representation for making a prototype in three dimensions (Askeland, 1984).
The current study examines these company characteristics to determine if earnings management exists relative to the accrual of accretion expense under SFAS No.
These blue and red shifts broaden the spectrum of X rays emitted from the iron atoms in the accretion disk.
Results: Calcium supplementation significantly influenced bone accretion in young females during the pubertal growth spurt.
If strata are correlative from one to the other, such relationships may indicate there was no major terrane; if they are not correlative, the accretion boundaries are cryptic.
According to Karpat, "The genesis of Turkish nationalism was a multifaceted process occurring in several stages of identity accretion proceeding from universal Ottomanism and Islamism to specific ethnic Turkishness and Turkism"(13).
Although this accumulation is most conspicuous in the tonsils, progressive accretion of these esters also occurs in nerves (neuropathy) and vessels (atherosclerosis).
This book will make more comprehensible how a slow accretion of architectural plans, political decisions, and the mundane processes of requisitions, orders, shipments and lists can create the unthinkable.