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==See Also==
==See Also==
* [[Black stars]] <ref>[http://arxiv.org/abs/0902.0346v2 Small, dark, and heavy: But is it a black hole?], Matt Visser, Carlos Barcelo, Stefano Liberati, Sebastiano Sonego, February 2009</ref><ref>[http://www.scientificamerican.com/article.cfm?id=black-stars-not-holes How Quantum Effects Could Create Black Stars, Not Holes]</ref>
* [[Black star]] <ref>[http://arxiv.org/abs/0902.0346v2 Small, dark, and heavy: But is it a black hole?], Matt Visser, Carlos Barcelo, Stefano Liberati, Sebastiano Sonego, February 2009</ref><ref>[http://www.scientificamerican.com/article.cfm?id=black-stars-not-holes How Quantum Effects Could Create Black Stars, Not Holes]</ref>
* [[Boson star]]
* [[Boson star]]


Revision as of 04:50, 13 October 2011

An exotic star is a compact star composed of something other than electrons, protons, and neutrons balanced against gravitational collapse by degeneracy pressure or other quantum properties. These include quark and strange stars (composed of quark or strange matter) and the more speculative preon stars (composed of preons).

Exotic stars are largely theoretical, but observations released by the Chandra X-Ray Observatory on April 10, 2002 detected two candidate quark stars, designated RX J1856.5-3754 and 3C58, which had previously been thought to be neutron stars. Based on the known laws of physics, the former appeared much smaller and the latter much colder than they should, suggesting that they are composed of material denser than neutronium. However, these observations are met with skepticism by researchers who say the results were not conclusive.[who?]

Quark stars and strange stars

Main article: Quark star

It is possible that the neutrons will decompose into their component up and down quarks when sufficient gravitational pressure is applied. In this case, the star will shrink further and become denser, but it may survive in this new state indefinitely if no extra mass is added. It has become a very large nucleon. A star in this hypothetical state is called a quark star. If quark stars contain strange matter, then they are called strange stars. The pulsars RX J1856.5-3754 and 3C58 have been suggested as possible quark stars.

Electroweak stars

Main article: Electroweak star

An electroweak star is a theoretical type of exotic star, whereby the gravitational collapse of the star is prevented by radiation pressure resulting from electroweak burning, that is, the energy released by conversion of quarks to leptons through the electroweak force. This process occurs in a volume at the star's core approximately the size of an apple, containing about two Earth masses.[1]

The stage of life of a star that produces an electroweak star is theorized to occur after a supernova collapse. Electroweak stars are denser than quark stars, and may form when quark degeneracy pressure is no longer able to withstand gravitational attraction, but may still be withstood by electroweak burning radiation pressure. [2] This phase of a star's life may last upwards of 10 million years.[1][3][4][5]

Preon stars

A preon star is a proposed type of compact star made of preons, a group of hypothetical subatomic particles. Preon stars would be expected to have huge densities, exceeding 1023 kilogram per cubic meter—intermediate between quark stars and black holes.[clarification needed] They may have greater densities than quark stars and neutron stars although they are smaller and lighter than white dwarfs and neutron stars.[6] Preon stars could originate from supernova explosions or the big bang. Such objects could be detected in principle through gravitational lensing of gamma rays. Preon stars are a potential candidate for dark matter. However, current observations from particle accelerators speak against the existence of preons.

In general relativity, if the star collapses to a size smaller than its Schwarzschild radius, an event horizon will appear at that radius and the star will become a black hole. For a one solar mass object, the Schwarzchild radius is 3 km; so, to be consistent with general relativity, any Solar mass preon star would have to have a radius larger than this. A preon star having the same mass as Earth would be about the size of a tennis ball.

See Also

References

  1. ^ a b D. Shiga (4 January 2010). "Exotic stars may mimic big bang". New Scientist. Retrieved 2010-02-18.
  2. ^ "Theorists Propose a New Way to Shine -- And a New Kind of Star: 'Electroweak'". ScienceDaily. 15 December 2009. Retrieved 2009-12-16.
  3. ^ "Theorists propose a new way to shine — and a new kind of star". Astronomy Magazine. 15 December 2009. Retrieved 2009-12-16.
  4. ^ Tudor Vieru (15 December 2009). "New Type of Cosmic Objects: Electroweak Stars". Softpedia. Retrieved 2009-12-16.
  5. ^ *"Astronomers Predict New Class of 'Electroweak' Star"". Technology Review. 10 December 2009. Retrieved 2009-12-16.
  6. ^ Hannson, J (9 June 2005). "Preon stars: a new class of cosmic compact objects". Physics Letters B. 616 (1–2): 1–7. doi:10.1016/j.physletb.2005.04.034. Retrieved 8 September 2011. {{cite journal}}: Unknown parameter |coauthors= ignored (|author= suggested) (help)
  7. ^ Small, dark, and heavy: But is it a black hole?, Matt Visser, Carlos Barcelo, Stefano Liberati, Sebastiano Sonego, February 2009
  8. ^ How Quantum Effects Could Create Black Stars, Not Holes
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