accretion disk

noun Astronomy.
the rapidly spinning disk of gas that forms around the more compact component of a close binary star system as mass is transferred to the compact companion from the primary star.

1975–80 Unabridged
Based on the Random House Dictionary, © Random House, Inc. 2014.
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American Heritage
Science Dictionary
accretion disk  
A spinning disk of gas and dust surrounding a celestial object with an intense gravitational field, such as a star or a black hole. In binary star systems, the gravitational attraction of the denser star can pull matter from the other star into an accretion disk in its own orbit. The material in the accretion disk eventually spirals into the attracting star and adds to its mass. The gas in accretion disks that surround black holes becomes condensed and heated as it is sucked into the hole, emitting x-rays and other radiation that provide evidence for the presence of the black hole.
The American Heritage® Science Dictionary
Copyright © 2002. Published by Houghton Mifflin. All rights reserved.
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Example sentences
Infrared observations of a binary star reveal a larger, thicker disk of cool
  dusty material surrounds much of the accretion disk.
As that gas spirals inward, it forms an accretion disk that gets denser near
  the center.
The white dwarf usually rips material off its companion and pulls it inward to
  form a disk, known as an accretion disk.
The material settles around the pulsar's middle in a so-called accretion disk.
Image for accretion disk
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