Pulsars or neutron stars are the frantic corpses left behind by supernova explosions—the death of a colossal star. Pulsars are known for their small and extremely dense bodies, but a team of researchers has managed to identify a pulsar whose mass is much lower than they can explain. Its apparently inexplicable existence may make sense after discovering its composition; experts believe this pulsar may be largely composed of strange quarks, a fundamental particle.
The science and other stuff to know
Neutron stars, as their name suggests, are made mostly of neutrons. This is because they are the remnants of the abrupt gravitational collapse of massive stars in the twilight of their lives. When a star between 10 and 50 solar masses—typically known as a supergiant—suffers such an imbalance that it ends up exploding as a supernova, the inner layers compress and collapse under the gravitational pressure exerted on them by the upper layers.
If the star were even more massive, this collapse could result in a black hole, but instead of completely rupturing space-time, it collapses the stellar core matter into a small body that is extremely dense, rotates at an extremely high speed, and emits electromagnetic pulses that astronomers use to identify them and gauge their distance from Earth.
But in the HESS J1731-347 system, something out of the ordinary was observed. A pulsar lives in the rubble of a magnificent supernova and, according to the authors of an article recently published in Nature Astronomy, its origin and composition remain a mystery. It is that the 0.77 solar mass that the researchers determined for this pulsating star is significantly less than the 1.4 solar mass that astrophysicists know to be the lower bound of neutron star masses.
In their article, the authors propose that perhaps this pulsar suffered such enormous pressure that even the neutrons broke, and it ended up being formed by a kind of ultra-dense material made only of strange quarks, one of the types of fundamental particles that make up the particles of the atomic nucleus.
“If we look at the masses of neutron stars when measured accurately, they are all around 1.4 solar masses,” co-author Victor Doroshenko at the University of Tübingen in Germany told New Scientist. He and his colleagues think that it’s critical to comprehend how this pulsar formed in order to enhance models of star formation and evolution.
Particle physicists are intrigued by the idea that the pulsar might contain strange quarks because, in that case, they could be dealing with previously undiscovered behavior of these fundamental particles. This research could provide specialists with hints to complete the Standard Model of Particle Physics, the theory that aims to explain the nature of the building blocks of matter and the interactions between them.
As is always the case in astronomy: once a phenomenon is observed in the universe for the first time, at first it seems exotic and unique, but over time similar phenomena begin to be discovered and identified.
Astrophysicists know that they need to continue to watch all regions of the sky for other pulsars that have similar characteristics and that they will likely begin to detect them. In this way, they will obtain enough data to strengthen their models of stellar dynamics and also of fundamental physics.