There are countless stars in the Universe. One such is our sun. Do you know that they have a life cycle? When clouds of gas and other material either gain sufficient mass to begin a gravitational collapse then they result in the formation of a star.
Why do stars emit light?
There are continuous nuclear fissions that keep on happening in a star in which generally low mass atoms like hydrogen combines to form helium and emit energy. A part of this energy is emitted as light that we can see. A major part of this energy allows the stars to exist as they are because it stops atoms of stars to go a high gravitational compression.
Death of a star?
With continuous fusions in millions of years every star comes to a point where the energy emitted from fusion is not enough to trigger another fusion. This results in high gravitational compression further resulting in the death of a star.
Depending upon size and mass of a star its death results in three different things-
- A white dwarf
- A neutron star
- A black hole
When a small star like our sun runs out fusion fuel, it starts compressing generally to the size of a planet. Due to its high astronomic temperature it shines bright white. Hence the name white dwarfs.
The massive stars which are spread across light years, when they die they have such a large mass that due to compression the whole mass collapses into a single point in space. Its gravitational field is so high that even the light passing nearby cannot escape. Once the light is captured it remains inside its horizon forever.
This is so far the best end of a star. The death of a medium sized star at least 14.6 times the mass of our sun results in a neutron star. These are one of the most fascinating things in our Universe. As we discussed, the death of a star is that instant of time when it runs out of fusion fuel and the gravitational force comes into play. In white dwarfs matter is compressed till the barrier of electromagnetic forces allow. But, in neutron stars this is not the case. The gravitational force is high enough to not only compress two atoms together but also it compresses them close enough that the electrons and protons combine together to form neutron and neutrino. Neutrinos are as fast as the speed of light so they escape into space forever, leaving behind a very very high density mass. The only thing that is stopping them to further compress is Pauli’s exclusion principle. It is so dense that if you hold a small water droplet sized neutron star it will cause a gravitational field which is comparable to the gravitational field of earth. You can try to guess what will be your weight on a neutron star. You cannot even move your leg up from the ground, forget about standing straight. Rotating neutron stars are also known as pulsars because they produce strong magnetic fields which pulses at regular intervals. These magnetic fields result in particle acceleration around their magnetic poles as a result a very high energy light is emitted. These celestial bodies are hard to study because they emit a very wide range of electromagnetic waves in the electromagnetic spectrum.