Pulsars are generally thought to be rapidly rotating neutron stars. The maximum possible mass of a neutron star is not clearly understood. Recent observations appeared to find a pulsar that has nearly twice the mass of our Sun. Some astronomers though this discovery ruled out a class of objects that might also be pulsars, called quark stars. This comment points out that researchers must examine fundamental assumptions about how quarks cluster before they entirely rule out the existence of  quark stars acting as pulsars.

 

http://www.raa-journal.org/raa/index.php/raa/article/view/659