White Dwarfs & Neutron Stars – Quark Matter

It is believed that particles such as protons and neutrons (hadrons) are composed of yet more sub-atomic fermi particles called quarks. A total of six quarks is hypothesised to exist, coming in pairs (particle and antiparticle). They are: up, down; charmed, strange; truth, beauty. Their charges are +2/3 and -1/3 respectively. Hadrons are composed of three quarks bound together by what is called the colour force, transported by particles called gluons. This force is so strong that no single quark has ever been viewed experimentally. The charges of the three quarks add up to give the integer charge on the hadron.

Just as the energies of the degenerate electrons could be raised by compression such that neutrons were formed, it is supposed that at the centre of a neutron star there would be enough energy such that the neutrons would decompose into quarks. Hence, it would be degenerate quark pressure that prevents any further collapse of the neutron star.