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Quarks are the subatomic entities that combine to form heavy nuclear particles.
Neutrons, in turn, are the primary constituents of pulsars, the spinning cosmic lighthouses that emit periodic flashes of radio waves. Or so astronomers have generally believed. Pulsar masses are typically 40 percent greater than the Sun's, yet the objects span only tens of kilometers at most. In most theorists' eyes, neutron stars are the only way to make pulsars so small yet so massive. But a few theorists think that some pulsars might be made of strange matter, which would be even denser than the stuff neutron stars are made of.