Gravitation, which we believe (but aren’t yet certain) is inherently a quantum force, can be well-described by General Relativity up until we obtain singularities any non-singular state can work within General Relativity.Those particles come in two types: fermions (which obey the Pauli rule) and bosons (which ignore it), but electrons and quarks, as well as protons and neutrons, are all fermions.All of the matter we know of is made, fundamentally, out of discrete quantum particles.Here’s a refresher on the basics of how our quantum Universe works. What this means, if you attempt to visualize it, is that force carrying particles (like photons, gluons, etc.) must be exchanged between the various fermions in the interior of the object. ( Credit: Andrew Truscott & Randall Hulet (Rice U.))īut there’s a key realization in the mechanism that prevents matter from collapsing down to a singularity: forces must be exchanged. It’s why fermion-containing stellar remnants, like white dwarfs and neutron stars, can hold themselves up against gravitational collapse, as the Pauli Exclusion Principle limits the volume that a finite number of fermions can occupy. It does not apply to bosons, and hence there is no limit to, say, the number of identical photons that can coexist in the same quantum state. It only applies to fermions, however, like quarks and leptons. The Pauli exclusion principle prevents two fermions from coexisting in the same quantum system with the same quantum state. Under these conditions, not only up-and-down quarks, but heavier, normally unstable quarks, may become part of the stellar remnant’s interior. It’s conceivable that if you exceed the allowed density at the core of a neutron star, it might move on to an even more concentrated state of matter: a quark-gluon plasma, where densities are so great that it no longer makes sense to consider the matter in there as individual, bound structures. Whenever massive stars go supernova, they can make either a black hole (if they’re above a critical mass threshold), but more commonly they’ll see their cores collapse to form a neutron star, which is the densest, most massive thing we know of that falls short of becoming a black hole.Ī neutron star is basically an enormous atomic nucleus: a bound-together collection of neutrons that’s even more massive than the Sun but contained in a region of space just a few kilometers across. This is, unsurprisingly, something that occurs in nature all the time. Imagine the densest, most massive object you can create out of matter that falls just short of the threshold for becoming a black hole. Credit: NASA’s Goddard Space Flight Center Irrespective of their spin rates, neutron stars may be the densest physical objects nature can create without progressing to create a singularity, and typically have surface temperatures of several hundreds of thousands of degrees. The fastest-spinning neutron star we’ve ever discovered is a pulsar that revolves 766 times per second: faster than our Sun would spin if we collapsed it down to the size of a neutron star. This computer simulation of a neutron star shows charged particles being whipped around by a neutron star’s extraordinarily strong electric and magnetic fields.
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