A star with four or more solar masses has a dramatic and explosive end, leaving behind a neutron star or a black hole, depending on the star's initial mass.

Here's a breakdown:

* Neutron Star: Stars with initial masses between 4-8 times that of our Sun will eventually collapse into a neutron star. These are incredibly dense objects, packing the mass of the Sun into a sphere only about 12 miles across. This extreme density is achieved when the star's core collapses, crushing protons and electrons together to form neutrons.

* Black Hole: If the star's initial mass is greater than 8 solar masses, the gravitational collapse is so intense that even neutrons can't withstand the pressure. This results in a singularity, a point of infinite density where the laws of physics break down. This singularity is surrounded by an event horizon, a point of no return where even light cannot escape. This forms a black hole.

Summary:

* 4-8 solar masses: Neutron star

* Greater than 8 solar masses: Black hole

These remnants represent the final stages of stellar evolution, offering fascinating insights into the extreme forces that shape the universe.