Stars-Death

At the time of a star birth,the giant clouds give birth to mainly three types of stars,which are the Low-mass star,mid sized star and the Massive stars.

The low-mass stars will develop into a red giant , but never fuse helium as the Mid-sized stars do; otherwise, it will simply contract until electron degeneracy pressure halts its collapse, thus directly turning into a white dwarf.

A white dwarf  compared  with the Earth 

At the same time the Mid-sized stars develops helium in its core an when it get close to its end the core becomes hot enough for the helium fusion to take place.After the star has consumed the helium at the core, fusion continues in a shell around a hot core of carbon and oxygen.At this stage more energy is released in the form of powerful stellar winds and violent pulsations 

Helium burning reactions are extremely sensitive to temperature, which causes great instability. Huge pulsations build up and eventually give the outer layers of the star enough kinetic energy to be ejected, potentially forming a planetary nebula. At the center of the nebula remains the core of the star, which cools down to become a small but dense white dwarf.

A black hole

The massive stars turn them selves into black holes after the supernova.If a star is 10 times more massive than the sun,no known force can stop the increasing gravity,and it will collapse to a point of infinite density.Before this stage is reached,within a certain radius,light itself becomes trapped,and the object becomes invisible,and becomes a black hole.Black holes are the densest areas in the Universe.