Black dwarf

A black dwarf is a theoretical stellar remnant, specifically a white dwarf that has cooled sufficiently that it no longer emits significant heat or light. Because the time required for a white dwarf to reach this state is calculated to be longer than the current age of the universe (13.8 billion years), no black dwarfs are expected to exist in the universe now, and the temperature of the coolest white dwarfs is one observational limit on the age of the universe.[1]

The name "black dwarf" has also been applied to substellar objects that do not have sufficient mass, less than approximately 0.08 M, to maintain hydrogen-burning nuclear fusion.[2][3] These objects are now generally called brown dwarfs, a term coined in the 1970s.[4][5] Black dwarfs should not be confused with black holes or black stars.



A white dwarf is what remains of a main-sequence star of low or medium mass (below approximately 9 to 10 solar masses (M)) after it has either expelled or fused all the elements for which it has sufficient temperature to fuse.[1] What is left is then a dense sphere of electron-degenerate matter that cools slowly by thermal radiation, eventually becoming a black dwarf.[6][7] If black dwarfs were to exist, they would be extremely difficult to detect, because, by definition, they would emit very little radiation. They would, however, be detectable through their gravitational influence.[8] Various white dwarfs cooled below 3900 K (M0 spectral class) were found in 2012 by astronomers using MDM Observatory's 2.4-meter telescope. They are estimated to be 11 to 12 billion years old.[9]

Because the far-future evolution of stars depends on physical questions which are poorly understood, such as the nature of dark matter and the possibility and rate of proton decay, it is not known precisely how long it will take white dwarfs to cool to blackness.[10], § IIIE, IVA. Barrow and Tipler estimate that it would take 1015 years for a white dwarf to cool to 5 K;[11] however, if weakly interacting massive particles (WIMPs) exist, it is possible that interactions with these particles will keep some white dwarfs much warmer than this for approximately 1025 years.[10], § IIIE. If protons are not stable, white dwarfs will also be kept warm by energy released from proton decay. For a hypothetical proton lifetime of 1037 years, Adams and Laughlin calculate that proton decay will raise the effective surface temperature of an old one-solar-mass white dwarf to approximately 0.06 K. Although cold, this is thought to be hotter than the cosmic background radiation temperature 1037 years in the future.[10], §IVB.

Future of the Sun

Once the Sun stops fusing helium in its core and ejects its layers in a planetary nebula in about 8 billion years, it will become a white dwarf and, over trillions of years time, eventually will no longer emit any light. After that, the Sun will not be visible to the equivalent of the naked human eye, removing it from optical view even if the gravitational effects are evident. The estimated time for the Sun to cool enough to become a black dwarf is about 1015 (1 quadrillion) years, though it could take much longer than this, if weakly interacting massive particles (WIMPs) exist, as described above.

See also

  • Degenerate matter – Collection of free, non-interacting particles with a pressure and other physical characteristics determined by quantum mechanical effects
  • Heat death of the universe – A possible end of the universe


  1. ^ a b §3, Heger, A.; Fryer, C. L.; Woosley, S. E.; Langer, N.; Hartmann, D. H. (2003). "How Massive Single Stars End Their Life". Astrophysical Journal. 591 (1): 288–300. arXiv:astro-ph/0212469. Bibcode:2003ApJ...591..288H. doi:10.1086/375341.
  2. ^ R. F. Jameson; M. R. Sherrington & A. R. Giles (October 1983). "A failed search for black dwarfs as companions to nearby stars". Royal Astronomical Society. 205: 39–41. Bibcode:1983MNRAS.205P..39J. doi:10.1093/mnras/205.1.39P.
  3. ^ Kumar, Shiv S. (1962). "Study of Degeneracy in Very Light Stars". Astronomical Journal. 67: 579. Bibcode:1962AJ.....67S.579K. doi:10.1086/108658.
  4. ^ brown dwarf, entry in The Encyclopedia of Astrobiology, Astronomy, and Spaceflight, David Darling, accessed online May 24, 2007.
  5. ^ Tarter, Jill (2014), "Brown Is Not a Color: Introduction of the Term 'Brown Dwarf'", in Joergens, Viki (ed.), 50 Years of Brown Dwarfs – From Prediction to Discovery to Forefront of Research, Astrophysics and Space Science Library, 401, Springer, pp. 19–24, doi:10.1007/978-3-319-01162-2_3, ISBN 978-3-319-01162-2
  6. ^ Johnson, Jennifer. "Extreme Stars: White Dwarfs & Neutron Stars" (PDF). Ohio State University. Retrieved 2007-05-03.
  7. ^ Richmond, Michael. "Late stages of evolution for low-mass stars". Rochester Institute of Technology. Retrieved 2006-08-04.
  8. ^ Charles Alcock; Robyn A. Allsman; David Alves; Tim S. Axelrod; Andrew C. Becker; David Bennett; Kem H. Cook; Andrew J. Drake; Ken C. Freeman; Kim Griest; Matt Lehner; Stuart Marshall; Dante Minniti; Bruce Peterson; Mark Pratt; Peter Quinn; Alex Rodgers; Chris Stubbs; Will Sutherland; Austin Tomaney; Thor Vandehei; Doug L. Welch (1999). "Baryonic Dark Matter: The Results from Microlensing Surveys". In the Third Stromlo Symposium: The Galactic Halo. 165: 362. Bibcode:1999ASPC..165..362A.
  9. ^ "12-Billion-Year-Old White-Dwarf Stars Only 100 Light-Years Away".
  10. ^ a b c Fred C. Adams & Gregory Laughlin (April 1997). "A Dying Universe: The Long Term Fate and Evolution of Astrophysical Objects". Reviews of Modern Physics. 69 (2): 337–372. arXiv:astro-ph/9701131. Bibcode:1997RvMP...69..337A. doi:10.1103/RevModPhys.69.337.
  11. ^ Table 10.2, Barrow, John D.; Tipler, Frank J. (1988). The Anthropic Cosmological Principle. Oxford University Press. ISBN 978-0-19-282147-8. LCCN 87028148.
Anderton Boat Lift

The Anderton Boat Lift is a two caisson lift lock near the village of Anderton, Cheshire, in North West England. It provides a 50-foot (15.2 m) vertical link between two navigable waterways: the River Weaver and the Trent and Mersey Canal. The structure is designated as a scheduled monument, and is included in the National Heritage List for England.Built in 1875, the boat lift was in use for over 100 years until it was closed in 1983 due to corrosion. Restoration started in 2001 and the boat lift was re-opened in 2002. The lift and associated visitor centre and exhibition are operated by the Canal & River Trust. It is one of only two working boat lifts in the United Kingdom; the other is the Falkirk Wheel in Scotland.

Apis andreniformis

Apis andreniformis, or the black dwarf honey bee, is a relatively rare species of honey bee whose native habitat is the tropical and subtropical regions of Southeast Asia.A. andreniformis was the fifth honey bee species to be described of the seven known species of Apis. Until recently, however, the actual identity of the species was poorly understood. It was not recognized as its own species, but was instead considered to be a part of the species Apis florea. Recent studies have highlighted notable differences between the bees and have thus separated them into distinct species.

Black Dwarf (comics)

Black Dwarf is a fictional character appearing in American comic books published by Marvel Comics. He is a prominent member of the Black Order, a team of aliens who work for the titan Thanos.

Black Dwarf appeared as Cull Obsidian, one of the Children of Thanos, in the Marvel Cinematic Universe films Avengers: Infinity War (2018) and Avengers: Endgame (2019), portrayed by Terry Notary.

Black Dwarf (personage)

David Ritchie (1740–1811), known also as David of Manor Water, Bow'd Davie, Crooked David, and most notably the Black Dwarf, was a dwarf, the son of a quarryman at the slate quarries of Stobo. He was the inspiration for Sir Walter Scott's novel, The Black Dwarf. Scott visited him in 1797.He was brought up as a brushmaker in Edinburgh, but was disliked because of his appearance. He eventually settled in a stone cottage on the banks of Manor Water near the town of Peebles, Scotland. The door of the cottage was about 3 feet and 6 inches high, and the ceiling was just high enough for him to stand inside. The superstitious locals feared he could cast the evil eye on them, blamed him for any problems with their livestock, and generally avoided him.He never wore shoes, which would not fit on his misshapen feet. Instead, he wrapped his legs and feet in cloth. He walked with the help of a staff considerably taller than himself.Sources described him as being irritable and having a shrill, dissonant laugh, but he is also described as an intellectual who enjoyed reading Milton's Paradise Lost and ballads by William Shenstone.

Black Order (comics)

The Black Order is a fictional supervillain team appearing in American comic books published by Marvel Comics.

The Black Order appeared in the Marvel Cinematic Universe films Avengers: Infinity War (2018) and Avengers: Endgame (2019). They were also known as the Children of Thanos.

Black dwarf hornbill

The black dwarf hornbill or western little hornbill (Horizocerus hartlaubi) is a species of hornbill in the family Bucerotidae. It is found in Angola, Cameroon, Central African Republic, Republic of the Congo, Democratic Republic of the Congo, Ivory Coast, Equatorial Guinea, Gabon, Ghana, Guinea, Liberia, Nigeria, Sierra Leone, South Sudan, Togo, and Uganda.

Black dwarf porcupine

The black dwarf porcupine, also known as Koopman's porcupine, Coendou nycthemera, is a porcupine species from the New World porcupine family endemic to northern Brazil. It occurs in the Amazon rainforest east of the Madeira River and south of the Amazon River. It inhabits primary forest and possibly second growth. It was described as Coendou koopmani by Charles O. Handley Jr. and Ronald H. Pine in 1992, but was subsequently found to be identical to a species described in 1818. It is nocturnal and herbivorous.

Bright giant

The luminosity class II in the Yerkes spectral classification is given to bright giants. These are stars which straddle the boundary between ordinary giants and supergiants, based on the appearance of their spectra.

Candlemass (album)

Candlemass is the eighth studio album by Swedish doom metal band Candlemass released in 2005. This was the band's last album with singer Messiah Marcolin.

A video for the album's opener, "Black Dwarf", was made. The song "Witches" was also included in the soundtrack for the 2009 video game Brütal Legend.

Dwarf star

A dwarf star is a star of relatively small size and low luminosity. Most main sequence stars are dwarf stars. The term was originally coined in 1906 when the Danish astronomer Ejnar Hertzsprung noticed that the reddest stars—classified as K and M in the Harvard scheme could be divided into two distinct groups. They are either much brighter than the Sun, or much fainter. To distinguish these groups, he called them "giant" and "dwarf" stars, the dwarf stars being fainter and the giants being brighter than the Sun. Most stars are currently classified under the Morgan Keenan System using the letters O, B, A, F, G, K, and M, a sequence from the hottest: O type, to the coolest: M type. The scope of the term "dwarf" was later expanded to include the following:

Dwarf star alone generally refers to any main-sequence star, a star of luminosity class V: main-sequence stars (dwarfs). Example: Achernar (B6Vep)Red dwarfs are low-mass main-sequence stars.

Yellow dwarfs are main-sequence (dwarf) stars with masses comparable to that of the Sun.

Orange dwarfs are K-type main-sequence stars.

A blue dwarf is a hypothesized class of very-low-mass stars that increase in temperature as they near the end of their main-sequence lifetime.

A white dwarf is a star composed of electron-degenerate matter, thought to be the final stage in the evolution of stars not massive enough to collapse into a neutron star or black hole—stars less massive than roughly 9 solar masses.

A black dwarf is a white dwarf that has cooled sufficiently such that it no longer emits any visible light.

A brown dwarf is a substellar object not massive enough to ever fuse hydrogen into helium, but still massive enough to fuse deuterium—less than about 0.08 solar masses and more than about 13 Jupiter masses.

International Marxist Group

See also the International Marxist Group (Germany).The International Marxist Group (IMG) was a Trotskyist group in Britain between 1968 and 1982. It was the British Section of the Fourth International. It had around 1,000 members and supporters in the late 1970s. In 1980, it had 682 members; by 1982, when it changed its name to the Socialist League, membership had fallen to 534.

Jedediah Cleishbotham

Jedediah Cleishbotham is an imaginary editor in Walter Scott's Tales of My Landlord. According to Scott, he is a "Schoolmaster and Parish-clerk of Gandercleugh." Scott claimed that he had sold the stories to the publishers, and that they had been compiled by fellow schoolmaster Peter Pattieson from tales collected from the landlord of the Wallace Inn at Gandercleugh. For more information, see the introduction to The Black Dwarf by Scott.

King of the Grey Islands

King of the Grey Islands is the ninth studio album by Swedish doom metal band Candlemass released on 22 June 2007. This is the first album recorded following the departure of vocalist Messiah Marcolin, who left the band during the pre-production phase of the album. He was replaced by Robert Lowe, who would stay with the band until his departure in June 2012.

A digipak version contains two bonus studio session tracks with Robert Lowe. The album was also released as a double vinyl LP with the bonus track "Edgar Grey". A tin box set edition (limited to 500 copies) was also released, which included a bonus 3" CD with two bonus tracks: "Black Dwarf" and "Demonia 6 (early version)". "Black Dwarf" is a re-recording with Lowe on vocals. These songs also appear on the "Black Dwarf" 7".

Upon its release, the album was met with widespread acclaim from both critics and fans.

Lead star

A lead star is a low-metallicity star with an overabundance of lead and bismuth as compared to other products of the S-process.

Old Mortality

Old Mortality is a novel by Walter Scott set in the period 1679–89 in south west Scotland. It forms, along with The Black Dwarf, the 1st series of Scott's Tales of My Landlord. The two novels were published together in 1816. Old Mortality is considered one of Scott's best novels.

Scott's original title was The Tale of Old Mortality, but is generally shortened in most references.

Q star

A Q-Star, also known as a grey hole, is a hypothetical type of a compact, heavy neutron star with an exotic state of matter. The Q stands for a conserved particle number. A Q-Star may be mistaken for a stellar black hole.

The Black Dwarf

The Black Dwarf (1817–1824) was a satirical radical journal of early 19th century Britain. It was published by Thomas Jonathan Wooler, starting in January 1817 as an eight-page newspaper, then later becoming a 32-page pamphlet. It was priced at 4d a week until the Six Acts brought in by the Government in 1819 to suppress radical unrest forced a price increase to 6d. In 1819 it was selling in issues of roughly 12,000 to working people such as James Wilson at a time when the reputable upper-middle class journal Blackwood's Magazine sold in issues of roughly 4,000 copies.

The Black Dwarf (newspaper)

The Black Dwarf was a political and cultural newspaper published between May 1968 and 1972 by a collective of socialists in the United Kingdom. It is often identified with Tariq Ali who edited and published the newspaper until 1970, when the editorial board split between Leninist and non-Leninist currents.

The Leninists, including Ali and other members of the International Marxist Group, went on to found the Red Mole.

The Black Dwarf newspaper published a special edition in autumn 1968 devoted entirely to the Bolivian Diaries of Che Guevara, in a translation first published by Ramparts in the United States. It included an introduction by Fidel Castro. This edition appeared to be in response to a version of the diaries put out by "some publishers in league with those who murdered Che".

The editorial and production group included Ali, Clive Goodwin, Robin Fior, David Mercer, Mo Teitlebaum, Douglas Gill, Adrian Mitchell, Sheila Rowbotham, Bob Rowthorn, D.A.N. Jones, Sean Thompson, Neil Lyndon, Roger Tyrrell and Fred Halliday.

Black Dwarf took its name from the 19th-century radical paper of that name which was first published in 1817.

The Black Dwarf (novel)

Walter Scott's novel The Black Dwarf was part of his Tales of My Landlord, 1st series, published along with Old Mortality on 2 December 1816 by William Blackwood, Edinburgh, and John Murray, London. Originally the four volumes of the series were to tell separate stories, but Old Mortality came to occupy three of them.

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