A hot infant and a cold adult — the same neutron star looks different. Just born in a supernova explosion, it is scorching hot at tens of billions of degrees. But as time passes, it cools, contracting like cooling metal. For the star PSR J1012+5307, this transition means an almost twofold reduction in radius.
The scientists used relativistic mean-field theory to model the star's matter with the possible presence of hyperons — particles containing strange quarks. It turned out that in the cold state, the differences between purely nucleonic matter and matter with hyperons are almost imperceptible. This means that confirming the presence of hyperons in the core of PSR J1012+5307 with current observations is extremely difficult. But future precise measurements of pulsar masses from their very birth may provide the answer.
The temperature of 30 MeV in question is about 20,000 times hotter than the center of the Sun.