Quark star

Source: Wikipedia, the free encyclopedia.
Not to be confused with Quasar or Q star.

A quark star is a hypothetical type of

quark matter, a continuous state of matter consisting of free quarks.[1]

Background

Some

electromagnetic forces, will occur and hinder total gravitational collapse
.

If these ideas are correct, quark stars might occur, and be observable, somewhere in the universe. Such a scenario is seen as scientifically plausible, but has not been proven observationally or experimentally; the very extreme conditions needed for stabilizing quark matter cannot be created in any laboratory and has not been observed directly in nature. The stability of quark matter, and hence the existence of quark stars, is for these reasons among the unsolved problems in physics.

Numerical simulations of the physics inside neutron stars suggests that the core of these stars could contain deconfined quark-gluon plasma.[3][4][5] The idea is that in the core the internal pressure needed for quark degeneracy – the point at which neutrons break down into a form of dense quark matter.

History

The analysis about quark stars was first proposed in 1965 by Soviet physicists D. D. Ivanenko and D. F. Kurdgelaidze.[6][7] Their existence has not been confirmed.

The

K cannot be recreated artificially, as there are no known methods to produce, store or study "cold" quark matter directly as it would be found inside quark stars. The theory predicts quark matter to possess some peculiar characteristics under these conditions.[citation needed
]

Formation

Mass–radius relations for models of a neutron star with no exotic states (red) and a quark star (blue)[9]

It is hypothesized that when the

neutron-degenerate matter, which makes up neutron stars, is put under sufficient pressure from the star's own gravity or the initial supernova creating it, the individual neutrons break down into their constituent quarks (up quarks and down quarks), forming what is known as quark matter. This conversion may be confined to the neutron star's center or it might transform the entire star, depending on the physical circumstances. Such a star is known as a quark star.[10][11]

Stability and strange quark matter

Ordinary quark matter consisting of up and down quarks has a very high Fermi energy compared to ordinary atomic matter and is stable only under extreme temperatures and/or pressures. This suggests that the only stable quark stars will be neutron stars with a quark matter core, while quark stars consisting entirely of ordinary quark matter will be highly unstable and re-arrange spontaneously.[12][13]

It has been shown that the high Fermi energy making ordinary quark matter unstable at low temperatures and pressures can be lowered substantially by the transformation of a sufficient number of up and down quarks into

strange quark matter and it is speculated and subject to current scientific investigation whether it might in fact be stable under the conditions of interstellar space (i.e. near zero external pressure and temperature). If this is the case (known as the Bodmer–Witten assumption), quark stars made entirely of quark matter would be stable if they quickly transform into strange quark matter.[14]

Strange stars

Main article: Strange star

Stars made of

strange quark matter are known as strange stars. These form a distinct subtype of quark stars.[14]

Theoretical investigations have revealed that quark stars might not only be produced from neutron stars and powerful supernovas, they could also be created in the early cosmic phase separations following the Big Bang.[12] If these primordial quark stars transform into strange quark matter before the external temperature and pressure conditions of the early Universe makes them unstable, they might turn out stable, if the Bodmer–Witten assumption holds true. Such primordial strange stars could survive to this day.[12]

Characteristics

Quark stars have some special characteristics that separate them from ordinary neutron stars. Under the physical conditions found inside neutron stars, with extremely high densities but temperatures well below 1012 K, quark matter is predicted to exhibit some peculiar characteristics. It is expected to behave as a

Fermi liquid and enter a so-called color-flavor-locked (CFL) phase of color superconductivity, where "color" refers to the six "charges" exhibited in the strong interaction, instead of the two charges (positive and negative) in electromagnetism. At slightly lower densities, corresponding to higher layers closer to the surface of the compact star, the quark matter will behave as a non-CFL quark liquid, a phase that is even more mysterious than CFL and might include color conductivity and/or several additional yet undiscovered phases. None of these extreme conditions can currently be recreated in laboratories so nothing can be inferred about these phases from direct experiments.[15]

Observed overdense neutron stars

At least under the assumptions mentioned above, the probability of a given neutron star being a quark star is low,[citation needed] so in the Milky Way there would only be a small population of quark stars. If it is correct, however, that overdense neutron stars can turn into quark stars, that makes the possible number of quark stars higher than was originally thought, as observers would be looking for the wrong type of star.[citation needed]

A neutron star without deconfinement to quarks and higher densities cannot have a rotational period shorter than a millisecond; even with the unimaginable gravity of such a condensed object the centrifugal force of faster rotation would eject matter from the surface, so detection of a pulsar of millisecond or less period would be strong evidence of a quark star.

Observations released by the

RX J1856
is a quark star has been excluded.

Another star, XTE J1739-285,[17] has been observed by a team led by Philip Kaaret of the University of Iowa and reported as a possible quark star candidate.

In 2006, You-Ling Yue et al., from Peking University, suggested that PSR B0943+10 may in fact be a low-mass quark star.[18]

It was reported in 2008 that observations of supernovae SN 2006gy, SN 2005gj and SN 2005ap also suggest the existence of quark stars.[19] It has been suggested that the collapsed core of supernova SN 1987A may be a quark star.[20][21]

In 2015, Zi-Gao Dai et al. from Nanjing University suggested that Supernova ASASSN-15lh is a newborn strange quark star.[22]

In 2022 it was suggested that GW190425, which likely formed as a merger between two neutron stars giving off gravitational waves in the process, could be a quark star.[23]

Other hypothesized quark formations

Apart from ordinary quark matter and strange quark matter, other types of quark-gluon plasma might hypothetically occur or be formed inside neutron stars and quark stars. This includes the following, some of which has been observed and studied in laboratories:

  • Robert L. Jaffe 1977, suggested a four-quark state with strangeness (qsqs).
  • Robert L. Jaffe 1977 suggested the H
    dibaryon
    , a six-quark state with equal numbers of up-, down-, and strange quarks (represented as uuddss or udsuds).
  • Bound multi-quark systems with heavy quarks (QQqq).
  • In 1987, a pentaquark state was first proposed with a charm anti-quark (qqqsc).
  • Pentaquark state with an antistrange quark and four light quarks consisting of up- and down-quarks only (qqqqs).
  • Light pentaquarks are grouped within an antidecuplet, the lightest candidate, Θ+, which can also be described by the diquark model of Robert L. Jaffe and Wilczek (QCD).
  • Θ++ and antiparticle Θ−−.
  • Doubly strange pentaquark (ssddu), member of the light pentaquark antidecuplet.
  • Charmed pentaquark Θc(3100) (uuddc) state was detected by the H1 collaboration.[24]
  • Tetraquark particles might form inside neutron stars and under other extreme conditions. In 2008, 2013 and 2014 the tetraquark particle of Z(4430), was discovered and investigated in laboratories on Earth.[25]

See also

  • Deconfinement – Phase of matter where certain particles can exist outside of a bound state
  • Neutron – Subatomic particle with no charge
    • Neutron matter
       – Type of dense exotic matter in physics
    • Neutron stars
       – Collapsed core of a massive star
  • Planck star – Hypothetical astronomical object
  • Quark-nova – Hypothetical violent explosion resulting from conversion of a neutron star to a quark star
  • Quantum chromodynamics – Theory of the strong nuclear interactions
  • Tolman–Oppenheimer–Volkoff limit – Upper bound to the mass of cold, nonrotating neutron stars
  • Degenerate matter – Type of dense exotic matter in physics
    • Neutron matter
       – Type of dense exotic matter in physics
    • Preon matter
       – Hypothetical subatomic particle
    • QCD matter – Hypothetical phases of matter
    • Quark–gluon plasma – Phase of quantum chromodynamics (QCD)
    • Quark matter
       – Hypothetical phases of matter
    • Strangelet – Type of hypothetical particle
  • Compact star
     – Classification in astronomy

References

  1. ^ Sutter, Paul (5 October 2023). "These Stars Are Like Nothing Else You'll Ever See". Popular Mechanics. Retrieved 6 July 2024.
  2. ^ Seife, Charles. "Quark Stars Get Real". Science.org.
  3. PMID 38114461
    .
  4. ^ Komoltsev, Oleg (4 January 2024). "New evidence for quark matter cores in massive neutron stars". University of Stavanger. Retrieved 17 June 2025.
  5. ^ Vuorinen, Aleksi (28 December 2023). "Further evidence for quark matter cores in massive neutron stars". University of Helsinki. Retrieved 17 June 2025.
  6. S2CID 119657479
    .
  7. S2CID 120712416
    .
  8. ISSN 0218-3013
    .
  9. ^ F. Douchin, P. Haensel, A unified equation of state of dense matter and neutron star structure, "Astron. Astrophys." 380, 151 (2001).
  10. ISBN 978-0471873167
    .
  11. ISBN 978-3-540-42340-9
    .
  12. ^
    doi:10.1103/PhysRevD.30.272
    .
  13. doi:10.1103/PhysRevD.30.2379
    .
  14. ^ a b Weber, Fridolin; Kettner, Christiane; Weigel, Manfred K.; Glendenning, Norman K. (1995). "Strange-matter Stars". Archived from the original on 2022-03-22. Retrieved 2020-03-26. in Kumar, Shiva; Madsen, Jes; Panagiotou, Apostolos D.; Vassiliadis, G. (eds.). International Symposium on Strangeness and Quark Matter, Kolymbari, Greece, 1-5 Sep 1994. Singapore: World Scientific. pp. 308–317.
  15. S2CID 14117263
    .
  16. S2CID 425112
    .
  17. ^ Shiga, David; "Fastest spinning star may have exotic heart" Archived 2012-08-25 at the Wayback Machine, New Scientist, 2007 February 20
  18. S2CID 18183996
    .
  19. ^ Chadha, Kulvinder Singh; "Second Supernovae Point to Quark Stars" Archived 2010-01-25 at the Wayback Machine, Astronomy Now Online, 2008 June 04
  20. S2CID 14402008
    .
  21. ^ Parsons, Paul; "Quark star may hold secret to early universe" Archived 2015-03-18 at the Wayback Machine, New Scientist, 2009 February 18
  22. S2CID 54823427
    .
  23. ^ "Strange quark star may have formed from a lucky cosmic merger". Space.com. 16 September 2022.
  24. S2CID 119375207.{{cite journal}}: CS1 maint: numeric names: authors list (link
    )
  25. ^ Koberlein, Brian (10 April 2014). "How CERN's discovery of exotic particles may affect astrophysics". Universe Today. Archived from the original on 14 April 2014. Retrieved 14 April 2014./

Sources and further reading
Retrieved from "https://en.wikipedia.org/w/index.php?title=Quark_star&oldid=1297095782"