What happens to massive stars?
At the end of their lives they go to a state of super nova.
Massive stars always end in an explosion, the super nova. As these stars implode they create layer upon layers of elements, each lower layer of greater mass than that the previous. At some point these imploding layers hit what is called "bounce back" at the stars core. It is at this point the star "explodes" but it is really just shedding its outer layers.
At the very end some of these stars become neutron stars or pulsars. Unfortunately, very little is known about these stars.