How stars die.

How stars die.

When we look up in the sky at night, we see the whole sky decorated with stars. But do you know what you see is just a fraction of them? There are approximately 200 billion stars just in the milky way galaxy and approximately 7 trillion galaxies in the observable Universe?

All stars go through a stable phase in which they shine steadily. Stars give heat and light by means of nuclear fusion. When stars run out of fuel, they die. Most of them die quietly, but most of them destroy themselves in a violent manner.

1. Small stars: When small stars run out of fuel, they fade away slowly. First, it begins to shrink its light fades as fuel runs out. Finally, when all the fuel is used up, the star becomes a black dwarf (a black dwarf is an earth-sized residue).
2. Medium star: A medium star-like Sun when uses up its hydrogen fuel in its core, nuclear fusion spreads outside the core, making the star expand into a red giant. Its core becomes so hot and dense that it starts to fuse helium atoms, but eventually, it runs out of helium too. Finally, it becomes a white dwarf (white dwarf is a dying core which later fades away and becomes a black dwarf), and its outer surface spreads into space which later gets recycled to form new stars.

3. Massive stars: These stars end their lives in a violent way. These stars are 8 times massive than the Sun. When the heat and pressure in a massive star become so great, it not only fuse hydrogen atoms to form helium, but it fuses helium and larger atoms to form elements like carbon. Due to this, the star swells and becomes a supergiant (largest star). Nuclear fusion carries on in its core forming heavier and heavier atoms until the core turns into iron. When this happens, the core no longer generates outward pressure to resist the crushing force of gravity, and the whole star starts to collapse, which causes a huge explosion (a supernova). The outer surface of the star is blasted into space, but the core continues to collapse in on itself. Later if the core is small and not much massive, then it becomes a neutron star (a neutron star is three times heavier than the Sun, it is a fast-spinning star and has unimaginable density), and if the core is too massive, it continues to collapse until its billions of times smaller then an atom, and finally bit becomes a black hole (a black hole has the intense force of gravity that nothing can escape from it not even light).

Star death depends on the mass of the star; more the mass more will be the force of gravity, due to which the core will be hotter and denser.

Our Sun is also a star ( a medium star), and it will also die like other stars, not in a violent way, but after 10 billion years, the Sun will expand in size and will destroy the earth.