Hypothetical star

A hypothetical star is a star, or type of star, that is speculated to exist but has yet to be definitively observed. Hypothetical types of stars have been conjectured to exist, have existed, or will exist in the future universe.[1][2][3]

Types

Scientifically speculated hypothetical types include:

Type Description Candidates Notes Citations
Anti-star A star composed of antimatter. Anti-helium nuclei have been detected. [4][5]
Blitzar Pulsar with enough mass to suddenly collapse into a black hole when the rotation speed slows. [6]
Blue dwarf Conjectured to develop after a red dwarf has exhausted most of its hydrogen. N/a The visible universe is not old enough for this form to come into existence. [7]
Black dwarf The final state for a star, like the Sun, that is too small to become a black hole or a neutron star. It would take a star like the Sun roughly a quadrillion (1015) years to reach this state, so none are believed to exist today. N/a The universe is not old enough for this form to come into existence. [1][8]
Black star A star predicted in semiclassical gravity which collapses into a black hole state but has neither a gravitational singularity nor an event horizon. none [9]
Boson star A star or astronomical object made of bosons, such as photons or gluons, rather than conventional matter. none [10][2]
Buchdahl star A stellar object at the upper bound on compactness. none [11]
Dark energy star A conjectured alternative to a black hole. none [12]
Dark matter star Conjectured to have existed early in the universe. JADES-GS-z13-0, JADES-GS-z12-0, and JADES-GS-z11-0 [1][2]
Dark star A theoretical construct based on Newtonian gravitation, of a star with gravity so strong that even light cannot escape. N/a This form cannot exist, as Newtonian gravitation breaks down under these conditions. It is a disproved hypothesis.
Electroweak star A star where gravitational collapse is prevented by radiation pressure resulting from electroweak burning. In this type of star, quarks are converted to leptons via the electroweak interaction. The core of the star would be hand-sized, containing perhaps two Earth masses, and might follow from the collapse of a quark star. none [13]
Frozen star A very-low-mass star with a surface temperature of perhaps 300 kelvins that could form in the far future, when the metallicity of the interstellar medium is higher than the current value. N/a The universe is not old enough for this form to come into existence. [14]
Fuzzball A formulation of black holes in string theory. none [15]
Gravastar An alternative to a black hole that denies the possibility of a singularity. none [16]
Hyperon star A massive neutron star containing hyperons. PSR J0348+0432 [17][18]
Iron star A final state for a star in the far future (101500 years) of the universe, when all matter is transmuted to iron via quantum tunneling. N/a The universe is not old enough for this form to come into existence. [8]
MECO Magnetospheric eternally collapsing object: a hypothetical alternative to black holes. Q0957+561 [19]
Planck star A star where the energy density is around the Planck density. The star will start to expand as soon as its density reaches the Planck constant. To the black hole, it expands instantly, but to the outside world, it takes eons to expand even the slightest. none [20]
Population III star The very earliest stars, virtually free of metals, believed to have existed in the early universe when the only common elements were primordial hydrogen and helium. none [21][1]
Preon star A star with a core composed of preons. none [22]
Q star (grey hole) A compact, heavy neutron star with an exotic state of matter where most light does not escape the star. Cygnus X-1 [23]
Quark star Star composed of quark matter or strange matter. 3C 58, PSR B0943+10, XTE J1739-285 [2][1][24]
Quasi-star A conjectured star from the early universe with a black hole at its center. The Cliff, MoM-BH*-1[25] [26]
Strange star A form of quark star, a neutron star with strange matter at its core, or star which is a ball of strange matter. none [27]
Thorne–Żytkow object A hybrid red giant, red supergiant, or Wolf–Rayet star whose core is a neutron star. HV 11417 [2][28]
White hole The polar opposite of a black hole, it ejects matter from its core into space. It is hypothetically formed when a region around a black hole experiences a loss in entropy, and will immediately collapse when the entropy is restored. The loss of entropy allows the black hole to travel back in time, so it will continue to suck matter up into its event horizon, but once one goes into the event horizon of a white hole, space-time is so distorted that it will always lead one to outside the event horizon, even if one tries to go to the singularity. GRB 060614 [29]

Specific stars

Specific hypothetical stars include:

Star Description Notes Citations
Nemesis A star proposed as a companion to the Sun by Richard A. Muller in 1984 This star was ruled out by all-sky surveys.[30] [31]
Coatlicue A star thought to be the reason for how the Sun (and many other stars) came to be, proposed by Matthieu Gounelle and Georges Meynet in 2012 [32][33]
3 Cassiopeiae A star recorded by astronomer John Flamsteed, but never seen again [34]
34 Tauri A star recorded by John Flamsteed, later revealed to have been the planet Uranus [35]

See also

References

  1. 1 2 3 4 5 Pearson, Ezzy (June 3, 2025). "5 hypothetical stars we've yet to discover". BBC Sky an Night Magazine. Retrieved 2026-08-22.
  2. 1 2 3 4 5 Betz, Eric (March 25, 2021). "Four crazy stars astronomers think might really exist". Astronomy Magazine. Retrieved 2026-08-22.
  3. ↑ Wenz, John (January 18, 2019). "Four Types of Stars That Will Not Exist for Billions or Even Trillions of Years". Smithsonian Magazine. Retrieved 2026-08-24.
  4. ↑ "Are There Anti-Stars (Made of Antimatter) Around Us?". SciTechDaily. July 10, 2022. Retrieved 2026-08-25.
  5. ↑ Dupourqué, Simon; et al. (April 20, 2021). "Constraints on the antistar fraction in the Solar System neighborhood from the 10-year Fermi Large Area Telescope gamma-ray source catalog". Physical Review D. 103 083016. doi:10.1103/PhysRevD.103.083016.
  6. ↑ Ravi, Vikram; Lasky, Paul D. (July 2014). "The birth of black holes: neutron star collapse times, gamma-ray bursts and fast radio bursts". Monthly Notices of the Royal Astronomical Society. 441 (3): 2433–2439. arXiv:1403.6327. Bibcode:2014MNRAS.441.2433R. doi:10.1093/mnras/stu720.
  7. ↑ Adams, F. C.; et al. (December 2004). García-Segura, G.; et al. (eds.). Red Dwarfs and the End of the Main Sequence. Gravitational Collapse: From Massive Stars to Planets. Revista Mexicana de Astronomía y Astrofísica (Serie de Conferencias). Vol. 22. pp. 46–49. Bibcode:2004RMxAC..22...46A.
  8. 1 2 Caplan, M. E. (2020). "Black Dwarf Supernova in the Far Future". Monthly Notices of the Royal Astronomical Society. 497 (4): 4357–4362. Bibcode:2020MNRAS.497.4357C. doi:10.1093/mnras/staa2262.
  9. ↑ Barceló, Carlos; et al. (October 2009). "Black Stars, Not Holes". Scientific American. 301 (4): 38–45. Bibcode:2009SciAm.301d..38B. doi:10.1038/scientificamerican1009-38. JSTOR 26001554.
  10. ↑ Alcubierre, Miguel; et al. (February 2023). "Boson stars and their relatives in semiclassical gravity". Physical Review D. 107 (4) 045017. id. 045017. arXiv:2212.02530. Bibcode:2023PhRvD.107d5017A. doi:10.1103/PhysRevD.107.045017.
  11. ↑ Chakrabarti, Soumya; et al. (April 2026). "On the stability of the objects of limiting compactness: Black hole and Buchdahl star". Physics Letters B. 875 140333. Elsevier. doi:10.1016/j.physletb.2026.140333.
  12. ↑ Banerjee, Ayan; et al. (March 2020). "Analytical model of dark energy stars". Modern Physics Letters A. 35 (10). id. 2050071. arXiv:1911.09546. Bibcode:2020MPLA...3550071B. doi:10.1142/S0217732320500716.
  13. ↑ Dai, De-Chang; et al. (December 2010). "Electroweak stars: how nature may capitalize on the standard model's ultimate fuel". Journal of Cosmology and Astroparticle Physics. 2010. arXiv:0912.0520. Bibcode:2010JCAP...12..004D. doi:10.1088/1475-7516/2010/12/004.
  14. ↑ Beech, Martin (March 28, 2019). Introducing the Stars: Formation, Structure and Evolution. Springer. p. 166. ISBN 9783030117047.
  15. ↑ Guo, Bin; et al. (July 2018). "Can we observe fuzzballs or firewalls?". Journal of High Energy Physics. 2018 (7). id. 162. arXiv:1711.01617. Bibcode:2018JHEP...07..162G. doi:10.1007/JHEP07(2018)162.
  16. ↑ Ray, Saibal; et al. (2020). "Gravastar: An alternative to black hole". International Journal of Modern Physics D. 29 (5). id. 2030004-260. Bibcode:2020IJMPD..2930004R. doi:10.1142/S0218271820300049.
  17. ↑ Zhao, Xian-Feng (2017). "Can the massive neutron star PSR J0348+0432 be a hyperon star?". Acta Physica Polonica B. 48 (2): 171. arXiv:1712.08870. Bibcode:2017AcPPB..48..171Z. doi:10.5506/APhysPolB.48.171. ISSN 0587-4254. S2CID 119207371.
  18. ↑ Zhao, Xian-Feng (December 23, 2017). "The hyperons in the massive neutron star PSR J0348+0432". Chinese Journal of Physics. 53 (4): 221–234. arXiv:1712.08854. doi:10.6122/CJP.20150601D.
  19. ↑ Robertson, Stanley L.; Leiter, Darryl J. (2006). "The Magnetospheric Eternally Collapsing Object (MECO) Model of Galactic Black Hole Candidates and Active Galactic Nuclei". In Kreitler, Paul V. (ed.). New Developments in Black Hole Research. New York, NY USA: Nova Science Publishers, Inc. p. 1. arXiv:astro-ph/0602453. Bibcode:2006ndbh.book....1R. ISBN 1-59454-641-X.
  20. ↑ Barrau, Aurélien; Rovelli, Carlo (December 2014). "Planck star phenomenology". Physics Letters B. 739: 405–409. arXiv:1404.5821. Bibcode:2014PhLB..739..405B. doi:10.1016/j.physletb.2014.11.020.
  21. ↑ Fraser, M.; et al. (June 2017). "The mass distribution of Population III stars". Monthly Notices of the Royal Astronomical Society. 468 (1): 418–425. arXiv:1511.03428. Bibcode:2017MNRAS.468..418F. doi:10.1093/mnras/stx480.
  22. ↑ Hansson, J.; Sandin, F. (June 2005). "Preon stars: a new class of cosmic compact objects". Physics Letters B. 616 (1–2): 1–7. arXiv:astro-ph/0410417. Bibcode:2005PhLB..616....1H. doi:10.1016/j.physletb.2005.04.034.
  23. ↑ Brecher, K. (May 1993). "Gray Holes". Bulletin of the American Astronomical Society. American Astronomical Society, 182nd AAS Meeting, #55.07. 25: 89. Bibcode:1993AAS...182.5507B.
  24. ↑ Weber, Fridolin; et al. (March 2013). "Structure of Quark Stars". Proceedings of the International Astronomical Union. 291: 61–66. arXiv:1210.1910. Bibcode:2013IAUS..291...61W. doi:10.1017/S1743921312023174.
  25. ↑ Naidu, Rohan P.; et al. (August 2026). "A gas-enshrouded and gas-reddened black hole at cosmic dawn". Nature. 656 (8127): 329–333. doi:10.1038/s41586-026-10846-4. ISSN 1476-4687. PMC 13468124. PMID 42587117.
  26. ↑ Begelman, Mitchell C.; et al. (July 2008). "Quasi-stars: accreting black holes inside massive envelopes". Monthly Notices of the Royal Astronomical Society. 387 (4): 1649–1659. arXiv:0711.4078. Bibcode:2008MNRAS.387.1649B. doi:10.1111/j.1365-2966.2008.13344.x.
  27. ↑ Yang, Shuhua; et al. (April 2023). "Confronting Strange Stars with Compact-Star Observations and New Physics". Universe. 9 (5). id. 202. arXiv:2304.09614. Bibcode:2023Univ....9..202Y. doi:10.3390/universe9050202.
  28. ↑ Thorne, Kip S.; Żytkow, Anna N. (March 15, 1977). "Stars with degenerate neutron cores. I – Structure of equilibrium models". The Astrophysical Journal. 212 (1): 832–858. Bibcode:1977ApJ...212..832T. doi:10.1086/155109.
  29. ↑ Bianchi, Eugenio; et al. (November 2018). "White holes as remnants: a surprising scenario for the end of a black hole". Classical and Quantum Gravity. 35 (22). id. 225003. arXiv:1802.04264. Bibcode:2018CQGra..35v5003B. doi:10.1088/1361-6382/aae550.
  30. ↑ Whitmire, Daniel P. (January 2016). "Periodic mass extinctions and the Planet X model reconsidered". Monthly Notices of the Royal Astronomical Society: Letters. 455 (1): L114–L117. arXiv:1510.03097. Bibcode:2016MNRAS.455L.114W. doi:10.1093/mnrasl/slv157.
  31. ↑ Muller, R. A. (August 1984). Evidence for a solar companion star: recent developments (PDF). International Astronomical Union symposium on the search for extraterrestrial life. Vol. 112. Boston, MA. Retrieved 2026-08-16.
  32. ↑ Gounelle, M.; Meynet, G. (2012). "Solar system genealogy revealed by extinct short-lived radionuclides in meteorites". Astronomy & Astrophysics. 545: A4. arXiv:1208.5879. Bibcode:2012A&A...545A...4G. doi:10.1051/0004-6361/201219031. S2CID 54970631.
  33. ↑ Gounelle, Matthieu (October 2015). "The abundance of 26Al-rich planetary systems in the Galaxy". Astronomy & Astrophysics. 582. id. A26. Bibcode:2015A&A...582A..26G. doi:10.1051/0004-6361/201526174.
  34. ↑ Ashworth, William B. (February 1980). "A Probable Flamsteed Observation of the Cassiopeia A Supernova". Journal for the History of Astronomy. 11 (1): 1–9. Bibcode:1980JHA....11....1A. doi:10.1177/002182868001100102. ISSN 0021-8286. S2CID 121684168.
  35. ↑ Sheehan, William; et al., eds. (2021). Neptune: From Grand Discovery to a World Revealed: Essays on the 200th Anniversary of the Birth of John Couch Adams. Springer Nature. p. 50. ISBN 978-3-030-54218-4.

Further reading

  • Schunck, F.E. and E.W. Mielke: "General relativistic boson stars", Class. Quantum. Grav. Vol. 20, R301 - R356 (2003)
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