Neutron stars could be more compact than black holes express
In the standard picture, black holes are the undisputed density champions: all their matter is squeezed into a single point. Imagine the entire mass of Mount Everest packed into a grain of salt. But physicists have found a theoretical trick. If you add tiny corrections to the ordinary law of gravity, corrections that only activate at mind-boggling densities, then neutron stars can crunch down even further, snatching the record. These corrections, born from spacetime curvature, act like extra support: the star doesn’t collapse into a black hole but stays as a sphere, just compressed to the absolute limit.
Researchers tested different models, varying the composition and tweaking the theory’s parameters. It turns out the behavior of these stars is universal — what they’re made of doesn’t matter. They remain stable even where, according to Einstein, they’d be doomed to collapse. On top of that, these objects can churn out gravitational waves — ripples in spacetime picked up by detectors like LIGO. So, lurking in the depths of space, there might be “almost-black-holes,” and we can actually hear them.
If a sugar cube were made of neutron star stuff, it would weigh as much as Mount Everest.
In science fiction, super-dense “neutronium” is a favorite material for impenetrable armor, like in Star Trek.