Neutronium

Neutronium (sometimes shortened to neutrium[1]) is a proposed name for a substance composed purely of neutrons. The word was coined by scientist Andreas von Antropoff in 1926 (before the discovery of the neutron) for the conjectured "element of atomic number zero" that he placed at the head of the periodic table.[2][3] However, the meaning of the term has changed over time, and from the last half of the 20th century onward it has been also used legitimately to refer to extremely dense substances resembling the neutron-degenerate matter theorized to exist in the cores of neutron stars; henceforth "degenerate neutronium" will refer to this. Science fiction and popular literature frequently use the term "neutronium" to refer to a highly dense phase of matter composed primarily of neutrons.

Neutronium and neutron stars

Main article: Neutron star

Neutronium is used in popular literature to refer to the material present in the cores of neutron stars (stars which are too massive to be supported by electron degeneracy pressure and which collapse into a denser phase of matter). This term is very rarely used in scientific literature, for three reasons:

When neutron star core material is presumed to consist mostly of free neutrons, it is typically referred to as neutron-degenerate matter in scientific literature.[4]

Neutronium and the periodic table

The term "neutronium" was coined in 1926 by Andreas von Antropoff for a conjectured form of matter made up of neutrons with no protons or electrons, which he placed as the chemical element of atomic number zero at the head of his new version of the periodic table. It was subsequently placed in the middle of several spiral representations of the periodic system for classifying the chemical elements, such as those of Charles Janet (1928), E. I. Emerson (1944), John D. Clark (1950) and in Philip Stewart's Chemical Galaxy (2005).

Although the term is not used in the scientific literature either for a condensed form of matter, or as an element, there have been reports that, besides the free neutron, there may exist two bound forms of neutrons without protons.[5] If neutronium were considered to be an element, then these neutron clusters could be considered to be the isotopes of that element. However, these reports have not been further substantiated.

Although not called "neutronium", the National Nuclear Data Center's Nuclear Wallet Cards lists as its first "isotope" an "element" with the symbol n and atomic number Z = 0 and mass number A = 1. This isotope is described as decaying to element H with a half life of 10.24±0.02 min.

Properties

Due to beta (β) decay of mononeutron and extreme instability of aforementioned heavier "isotopes", degenerate neutronium is not expected to be stable under ordinary pressures. Free neutrons decay with a half-life of 10 minutes, 11 seconds. A teaspoon of degenerate neutronium gas would have a mass of two billion tonnes, and if moved to standard temperature and pressure, would emit 57 billion joules of β decay energy in the first half-life (average of 95 MW of power).[16] This energy may be absorbed as the neutronium gas expands. Though, in the presence of atomic matter compressed to the state of electron degeneracy, the β decay may be inhibited due to Pauli exclusion principle, thus making free neutrons stable. Also, elevated pressures should make neutrons degenerate themselves. Compared to ordinary elements, neutronium should be more compressible due to the absence of electrically charged protons and electrons. This makes neutronium more energetically favorable than (positive-Z) atomic nuclei and leads to their conversion to (degenerate) neutronium through electron capture, a process which is believed to occur in stellar cores in the final seconds of the lifetime of massive stars, where it is facilitated by cooling via ν
e
emission. As a result, degenerate neutronium can have a density of 4×1017 kg/m3,[17] roughly 13 magnitudes denser than the densest known ordinary substances. It was theorized that extreme pressures may deform the neutrons into a cubic symmetry, allowing tighter packing of neutrons,[18] or cause a strange matter formation.

In fiction

The term "neutronium" has been popular in science fiction since at least the middle of the 20th century. It typically refers to an extremely dense, incredibly strong form of matter. While presumably inspired by the concept of neutron-degenerate matter in the cores of neutron stars, the material used in fiction bears at most only a superficial resemblance, usually depicted as an extremely strong solid under Earth-like conditions, or possessing exotic properties such as the ability to manipulate time and space. In contrast, all proposed forms of neutron star core material are fluids and are extremely unstable at pressures lower than that found in stellar cores. According to one analysis, a neutron star with a mass below about 0.2 solar masses will explode.[19]

Noteworthy appearances of neutronium in fiction include the following:

See also

References

  1. "Neutrium: The Most Neutral Hypothetical State of Matter Ever". io9.com. 2012. Retrieved 2013-02-11.
  2. von Antropoff, A. (1926). "Eine neue Form des periodischen Systems der Elementen" (pdf). Zeitschrift für Angewandte Chemie 39 (23): 722–725. doi:10.1002/ange.19260392303.
  3. Stewart, P. J. (2007). "A century on from Dmitrii Mendeleev: Tables and spirals, noble gases and Nobel prizes". Foundations of Chemistry 9 (3): 235–245. doi:10.1007/s10698-007-9038-x.
  4. Angelo, J. A. (2006). Encyclopedia of Space and Astronomy. Infobase Publishing. p. 178. ISBN 978-0-8160-5330-8.
  5. Timofeyuk, N. K. (2003). "Do multineutrons exist?". Journal of Physics G 29 (2): L9. arXiv:nucl-th/0301020. Bibcode:2003JPhG...29L...9T. doi:10.1088/0954-3899/29/2/102.
  6. Schirber, M. (2012). "Nuclei Emit Paired-up Neutrons". Physics 5: 30. Bibcode:2012PhyOJ...5...30S. doi:10.1103/Physics.5.30.
  7. Spyrou, A.; Kohley, Z.; Baumann, T.; Bazin, D.; et al. (2012). "First Observation of Ground State Dineutron Decay: 16Be". Physical Review Letters 108 (10): 102501. Bibcode:2012PhRvL.108j2501S. doi:10.1103/PhysRevLett.108.102501. PMID 22463404.
  8. Bertulani, C. A.; Baur, G. (1986). "Coincidence Cross-sections for the Dissociation of Light Ions in High-energy Collisions" (pdf). Nuclear Physics A 480 (3–4): 615–628. Bibcode:1988NuPhA.480..615B. doi:10.1016/0375-9474(88)90467-8.
  9. 1 2 Bertulani, C. A.; Canto, L. F.; Hussein, M. S. (1993). "The Structure And Reactions Of Neutron-Rich Nuclei" (pdf). Physics Reports 226 (6): 281–376. Bibcode:1993PhR...226..281B. doi:10.1016/0370-1573(93)90128-Z.
  10. Hagino, K.; Sagawa, H.; Nakamura, T.; Shimoura, S. (2009). "Two-particle correlations in continuum dipole transitions in Borromean nuclei". Physical Review C 80 (3): 1301. arXiv:0904.4775. Bibcode:2009PhRvC..80c1301H. doi:10.1103/PhysRevC.80.031301.
  11. MacDonald, J.; Mullan, D. J. (2009). "Big Bang Nucleosynthesis: The Strong Nuclear Force meets the Weak Anthropic Principle". Physical Review D 80 (4): 3507. arXiv:0904.1807. Bibcode:2009PhRvD..80d3507M. doi:10.1103/PhysRevD.80.043507.
  12. Kneller, J. P.; McLaughlin, G. C. (2004). "The Effect of Bound Dineutrons upon BBN". Physical Review D 70 (4): 3512. arXiv:astro-ph/0312388. Bibcode:2004PhRvD..70d3512K. doi:10.1103/PhysRevD.70.043512.
  13. Bertulani, C. A.; Zelevinsky, V. (2002). "Is the tetraneutron a bound dineutron-dineutron molecule?". Journal of Physics G 29 (10): 2431. arXiv:nucl-th/0212060. Bibcode:2003JPhG...29.2431B. doi:10.1088/0954-3899/29/10/309.
  14. Timofeyuk, N. K. (2002). "On the existence of a bound tetraneutron". arXiv:nucl-th/0203003 [nucl-th].
  15. Bevelacqua, J. J. (1981). "Particle stability of the pentaneutron". Physics Letters B 102 (2–3): 79–80. Bibcode:1981PhLB..102...79B. doi:10.1016/0370-2693(81)91033-9.
  16. "Neutrinos give neutron stars a chill". Ars Technica OpenForum. Retrieved 4 December 2013.
  17. Zarkonnen (2002). "Neutronium". Everything2.com. Retrieved 2013-02-11.
  18. Felipe J. Llanes-Estrada; Gaspar Moreno Navarro (2011). "Cubic neutrons". arXiv:1108.1859v1 [nucl-th].
  19. K. Sumiyoshi; S. Yamada; H. Suzuki; W. Hillebrandt (21 Jul 1997). "The fate of a neutron star just below the minimum mass: does it explode?". Max-Planck-Institut für Astrophysik, Germany; RIKEN, U. Tokyo, and KEK, Japan. arXiv:astro-ph/9707230. Given this assumption... the minimum possible mass of a neutron star is 0.189 (solar masses)
  20. "The Only Way to Kill Superman", Action Comics #376 (May 1969), DC Comics

Further reading

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