Y: When a star burns through most of its nuclear material, it can explode in a bright supernova and leave behind a dense core. If that core is massive enough, it’ll become a neutron star.
D: Most neutron stars are a mere fifteen miles in diameter. That makes them about the size of a moderate city.
Y: These objects, also called pulsars, are extremely dense. Just a sample the size of a sugar cube from a neutron star would be equal to a hundred million tons on Earth.
D: The compact neutron star is one possible end-point for a star. Beyond a certain mass limit, though, these cores collapse under their own gravity, and they become black holes.
Y: But scientists are still asking “What’s the absolute limit before a massive neutron star collapses into a black hole?”
D: One certain neutron star pushes these questions to new limits. In 2019, astronomers at Green Bank Observatory in West Virginia found a neutron star which is almost too massive to exist.
Y: At twice the mass of our own sun, this neutron star is still only a few miles in diameter. The intense gravitational force concentrated on its relatively small surface is close to the limit where it should collapse in on itself.
D: And this particular pulsar isn’t only interesting because of its incredible density. Scientists are still unsure what pulsars are made of.
Y: The more that we learn about what is happening to this star, the closer we get to the discovery of the tipping point at which gravity obliterates pulsars and transforms them forever into black holes.