After black holes, neutron stars, and white dwarfs, what is the 4th most dense type of stellar object?

I've seen stripped envelope subdwarfs compared to white dwarfs.

Are stripped envelope subdwarfs sort of pseudo-compact objects, a tier below white dwarfs in terms of density and gravitational pull?

Does the stripping of envelopes from red giants and the transformation into subdwarf class somehow cause the core to become more dense and compact, or do subdwarfs retain their density and gravity of their progenitor red giant phase?

Any information would be greatly appreciated!

2 points Federal_Speaker_6546

After black holes, neutron stars, and white dwarfs, Hot Subdwarfs (specifically sdB and sdO types) are generally considered the 4th most compact stellar objects.

Reference : https://arxiv.org/abs/2410.11663#:~:text=Hot%20subdwarf%20(SD)%20stars%20are,ejection%20as%20well%20as%20mergers.

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2 points NearABE

A brown dwarf. Jupiter and Saturn are close to the largest size things will get accreting interstellar gas. At 1.4 Jupiter radii the compression would exceed the volume increase and added gas makes it smaller. At 75 jupiter mass the diameter would be closer to Saturn’s.

Density increases if it is made of denser material. If a star’s envelop is stripped of the remnant likely has more helium than a normal brown dwarf.

Fragments from a type 1 supernova or a partially failed supernova could be more compact.

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