black dwarf

black dwarf

noun Astronomy.
See under white dwarf.
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white dwarf

noun Astronomy.
a star, approximately the size of the earth, that has undergone gravitational collapse and is in the final stage of evolution for low-mass stars, beginning hot and white and ending cold and dark (black dwarf)


Origin:
1920–25

Dictionary.com Unabridged
Based on the Random House Dictionary, © Random House, Inc. 2014.
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World English Dictionary
white dwarf
 
n
one of a large class of small faint stars of enormous density (on average 108 kg/m³) with diameters only about 1 per cent that of the sun, and masses less than the Chandrasekhar limit (about 1.4 solar masses). It is thought to mark the final stage in the evolution of a sun-like star

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Word Origin & History

black dwarf
in astrophysics, a kind of dead and lightless star, 1966, from black + dwarf.
Online Etymology Dictionary, © 2010 Douglas Harper
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American Heritage
Science Dictionary
black dwarf  
The theoretical celestial object that remains after a white dwarf has used up all of its fuel and cooled off completely to a solid mass of extremely dense, cold carbon. A white dwarf will eventually become a black dwarf unless it has a companion star from which it can take sufficient mass to pass the Chandrasekhar limit and collapse into a neutron star or black hole. No black dwarf has ever been observed. Because the estimated cooling time for a white dwarf is in the trillions of years, it is unlikely that there are many, if any, black dwarfs in our universe, which is only 12 to 18 billion years old. See Note at dwarf star.
white dwarf  
A small, extremely dense star characterized by high temperature and luminosity. A white dwarf is believed to be in its final stage of evolution, having either used up most of its nuclear fuel in its main-sequence stage, or else moved through a giant stage and shed any remaining fuel in its outer layer as a planetary nebula, leaving only a glowing core. Some 10 percent of all stars in the Milky Way are white dwarfs, but despite their intrinsic luminosity, they are so small that none are visible to the naked eye. See Note at dwarf.
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American Heritage
Cultural Dictionary

white dwarf definition


A kind of star about the size of the Earth. White dwarfs represent a final stage of the life cycle of stars similar to the sun; they are formed when the stars use up their fuel and can no longer support nuclear reactions.

The American Heritage® New Dictionary of Cultural Literacy, Third Edition
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Published by Houghton Mifflin Company. All rights reserved.
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