Quarks are the fundamental components of protons and neutrons, which make up the nucleus of atoms. The most dense objects known to exist today are neutron stars--stars composed entirely of tightly packed neutrons. A typical neutron star is some 16 miles across, yet has a mass one and a half times the mass of our Sun.

The question is, is a neutron star indeed the most dense object that exists? It is thought that if the neutrons are too tightly packed--if what scientists consider a neutron star is too dense--the resulting instability may lead to a further collapse, resulting in a second explosion and the creation of a quark star. The energy that powers that second explosion comes from neutrons breaking down into their component parts: quarks.