Apart from the black holes discussed in other posts, there is another class of bizarre objects in space called degenerate stars. These objects are given this name because of the behavior of the electrons or neutrons from which they are made.
It turns out that the electrons or in some cases the neutrons can hold a huge object up against the crushing effects of gravity similar to how bones in our body hold us up against the downward pull of gravity.
Our bones do not do a perfect job though. For those of us lucky enough to life a long life, one’s height eventually decreases by a fraction of an inch owing to the constant pull of gravity on our bodies.
By contrast, when electrons or in some special cases neutrons play the role of the ‘bones’ in stars, there is no shrinkage. The star is forever supported. But what is a degenerate star, anyway?
The most common types of degenerate stars are: brown dwarfs, white dwarfs, and neutron stars. Let us consider here the case of brown dwarfs. Brown dwarfs are small objects in both size and mass. Basically when an object is too big to be a planet and at the same time is too small to be a star it is flung into this category.
If a brown dwarf were just a bit more massive it would be able to start up a nuclear fusion reactor in its center. The resulting energy would go into heating up the hydrogen gas near to the center, and in the end the gas pressure would reach high enough levels to push back on the gravity.
In a brown dwarf there is no significant source of heat in the center from nuclear fusion or otherwise. All a brown dwarf has to stand ‘tall’ and face the crushing effect of gravity is the hydrogen gas it is made of.
Hydrogen is composed of one proton and one electron each, and it is the electrons in particular that push off of one another and act as a kind of pressure. This ‘electron degeneracy pressure’ pushes outward on a brown dwarf by an amount that can balance the gravitational effects, thereby supporting the entire ‘dwarf.’
And this is the way a brown dwarf can be stable even when it approaches old age, and without ever shrinking a bit over time as humans do. In sum, a brown dwarf has ‘good bones.’