Astronomers have found two collapsed stars that they say appear to be made of free-floating quarks, an exotic form of matter whose existence has been theorized but never before seen. If confirmed, the finding would enhance understanding of how matter behaves under extreme conditions. Earth-bound physicists have been trying to briefly create a form of quark matter at Brookhaven National Laboratory.
In atom-smasher experiments, physicists have shown that protons and neutrons in the atom's core are made of tightly bound trios of even smaller bits called quarks. Physicists infer the existence of such confined quarks from the debris of high-energy particle collisions. Some theorists have argued that certain collapsed stars may produce conditions in which neutrons will be broken down into a mass of unbound, free-floating quarks.