T Y R A N T

The Surprising Reason Why Neutron Stars Don’t All Collapse To Form Black Holes

“The measurements of the enormous pressure inside the proton, as well as the distribution of that pressure, show us what’s responsible for preventing the collapse of neutron stars. It’s the internal pressure inside each proton and neutron, arising from the strong force, that holds up neutron stars when white dwarfs have long given out. Determining exactly where that mass threshold is just got a great boost. Rather than solely relying on astrophysical observations, the experimental side of nuclear physics may provide the guidepost we need to theoretically understand where the limits of neutron stars actually lie.”

If you take a large, massive collection of matter and compress it down into a small space, it’s going to attempt to form a black hole. The only thing that can stop it is some sort of internal pressure that pushes back. For stars, that’s thermal, radiation pressure. For white dwarfs, that’s the quantum degeneracy pressure from the electrons. And for neutron stars, there’s quantum degeneracy pressure between the neutrons (or quarks) themselves. Only, if that last case were the only factor at play, neutron stars wouldn’t be able to get more massive than white dwarfs, and there’s strong evidence that they can reach almost twice the Chandrasekhar mass limit of 1.4 solar masses. Instead, there must be a big contribution from the internal pressure each the individual nucleon to resist collapse.