User:RexxS/scc3

Unproven core collapse processes

A companion star spiralling closer to a neutron star or black hole experiences elongation ("spaghettification") and lateral compression due to tidal forces. It is hypothesized by some scientists that this could be a fifth trigger for core collapse. Other scientists disagree.

These processes, unlike the four above, are not yet considered by astrophysicists to be established, although they have been studied.

External gravitational gradient

It was suggested in a 1996 paper that tidal forces could cause the centers of binary neutron stars to become denser as a result of each others' gravitational field, due to tidal forces. Tidal forces are known to have extreme effects; when an object approaches a black hole sufficiently closely the gravitational field can be so extreme that the object is potentially ripped apart ("spaghettification"). The same effect is also responsible for the ocean tides and the tidal locking of our moon.

Spaghettification also involves lateral compression due to the extreme gravitational gradient (see diagram). Tidal force calculations were carried out on inward-spiralling binary neutron stars and a white dwarf orbiting a black hole. The authors concluded that potentially in some circumstances the lateral compression in a companion star of a neutron star or black hole could be sufficient to trigger core collapse. Subsequent papers rejected or argued the possibility, or noted factors that had not been modeled. This or a similar mode of collapse may be proven or disproven in future.

Quark novae and exotic matter core collapse

Main articles: Quark nova, Quark star, Electroweak star, Exotic star, and Quark–gluon plasma

In the same way that massive stars can overcome electron degeneracy and collapse until prevented by neutron degeneracy, it has been widely speculated that neutron stars (or the neutron core of a massive star) could potentially overcome degeneracy pressure of neutrons. If validated, this would lead to a model whereby core collapse of a neutron core could occur and would be ultimately prevented by degeneracy pressure of quarks, the component parts of neutrons.

A quark nova is a hypothetical type of core collapse of a neutron star into a quark star that some scientists believe might happen when the degeneracy pressure of neutrons - but not their constituent quarks - is exceeded.. They are hypothesized to occur in an analogous manner to known forms of electron-degeneracy core collapse. If proven to occur such a collapse could release immense amounts of energy estimated to be as much as 10⁴⁷ J (due to the immense binding energy of quarks and gravitational forces involved), and could potentially explain gamma ray bursts which rank among the most energetic explosions in the observed universe, or could be responsible for further production of heavy elements such as platinum through r-process nucleosynthesis.

Unsolved problem in physics:

Quark matter. Quantum chromodynamics (QCD) predicts that a quark-gluon plasma should be formed at high temperature and density, and experiments tentatively suggest quark-gluon plasma has been created in the laboratory for very brief periods of time. What are the properties of this phase of matter?

(more unsolved problems in physics)

Direct evidence for quark-novae is scant, in part since they would theoretically be radio quiet; however recent observations of supernovae SN2006gy, SN2005gj and SN2005ap, and compact objects RX J1856.5-3754 and 3C58 may hint at their existence, although some candidates have been subsequently stated by other scientists to be "ruled out with high confidence" or modeled as having exotic matter only at their center. Speculatively, further types of core collapse could exist for degeneracy pressure of even smaller particles - quarks to preons, preons to their subcomponents, and so forth - but this is an area where we lack knowledge.