Astrophysics: Neutron stars with no foreign matter in their core

The new findings now speak against the hypothesis. As strange as objects are – they apparently don’t behave strangely at all. “It seems that these very exotic states of matter do not exist in the nucleus of a neutron star,” comments theoretical physicist George Pykerewicz of Florida State University. Then the phase transition in quark matter – if it exists at all – will only happen shortly past the critical threshold, from which a neutron star essentially collapses into a black hole. Its exact value is not known, it is believed to be about three solar masses. “The question is,” Watts says, “if a strange substance exists at high densities, when exactly did it form?”

If J0740 had gone through this phase transition and contained more easily compressible quark matter, it should have been more than nine to ten miles in size, according to Watts. But even if you take into account the uncertainties of the measurements, 22 kilometers in diameter would be a fairly obvious lower limit, according to Miller.

This means that if neutron stars produce quark matter, then only at some point beyond 2.1 solar masses. Protons and neutrons can be easily conserved even at the most extreme scales. “In any case, it seems that some models are now excluded,” Watts remarks.