Neutron & Quark Stars
A neutron star is a stellar husk packed with neutrons. Neutron stars are as compressed as normal matter can be.
In their extant state, these stars can collapse no further because of quantum degeneracy pressure: a property of the Pauli exclusion principle, which states that no 2 fermions (subatomic particles of matter) can occupy the same place at the same time.
Owing to furious quantum mechanics, neutron stars stay hot. Their spinning, at up to 1,000 revolutions per second, emits intense electromagnetic radiation that is received as directional pulses. Such a star is termed a pulsar: a portmanteau of pulsating star.
Pulsars directionally pulse radiation at regular intervals, so precise that some rival atomic clocks for their accuracy in timekeeping. Sometimes these pulses become temporally distorted – what has been termed starquakes. The cause is uncertain.
When a topological defect passes through a pulsar, its mass, radius, and internal structure may be altered, resulting in a pulsar ‘quake’. ~ Australian physicist Victor Flambaum
A neutron is made up of 3 subatomic quarks: 2 down and 1 up. While protons and neutrons are the core of normal matter, they do not occupy the lowest net energy possible. Under intense gravity, a greater degree of subatomic stability exists.
As it rotates, a neutron star is constantly shedding magnetic field energy. In cosmological time, the star’s spin slows. Centrifugal forces that kept the utmost gravity at bay weaken, yielding further squish.
As a spinning neutron star slows down, deep within, under intensifying gravity, neutron quarks shirk to an even lower energy level than normal matter. Neutrons convert to hyperons: a soup of up, down, and strange quarks.
The initial nucleation of strange quark matter runs amok once hyperons start to form. Core density increases, melting the star from the inside out. Quarks are liberated from their normally bound state.
A neutron star evolves into a quark star. The seed of strange quark matter spreads until it reaches the iron-rich crust. It then separates from the crust, collapsing into even greater density.
An intense shock wave is generated when the collapse concludes. A spectacular explosion ejects the crust and leftover neutrons in a quark nova.
Quark nova bits slam into earlier supernova remnants, causing another outburst of light, as happened when the star first exploded. The 2nd blast can occur anywhere from seconds to years after the original supernova. Such double explosions, in rapid succession, have been observed in multiple instances.
More conservative thinkers are just not open to the idea that free quarks exist in neutron stars. ~ American astrophysicist Fridolin Weber