We’ve all heard those stories and tales right? About how the people that pass away from this life turn into stars and shine in the night sky forever looking upon us. But did you know that stars too have lives? Well, technically, yes they do. Stars are also born, they too grow, live, get old, and then they die too! And just like us, stars too have different phases in their lives. One such phase in the life of the stars is the stage of White Dwarf Star, which is towards the end of their lives, like a prolonged old age. Let’s take a closer look.
Birth and Life Cycle of a Star
Let’s start with a quick brief about the life cycle of stars. The inception of stars’ lives takes place within Stellar Nebulae. These are massive clouds of gas and dust held together by gravity. It is this gravity that gradually pulls these gases together and amasses them into giant burning spheres of gases that we know as stars.
That’s a simplified way of understanding how stars are born. The huge mass of the stars creates such gravity that crushes the matter of the star itself together and burns them into nuclear fusion, generating an enormous amount of energy.
What follows next is the part of the stars’ lives that we are most familiar with- its youth and middle life, where it constantly burns Hydrogen in the fusion reaction to make Helium. The outward pressure generated from this reaction pushes against the inward force of the gravity of the star and keeps a balance that allows the stars to live. It’s like how our metabolism keeps us active and alive. From then the path of life of the stars diverges. Which path they follow is determined by their mass, and it is the average and small stars that go on to become the White Dwarf Stars near the end of their lives.
How is a White Dwarf Star Formed?
We know how stars generate energy, and that they do so through the process of nuclear fusion where Hydrogen is fused into Helium. So, when a star gets old and starts running out of fuel, that is, Hydrogen to burn in its core it starts fusing Helium into heavier elements. This marks the beginning of the death of the star. This fusion reaction creates an imbalance between the outwards pressure of energy and the inwards push of gravity. The star starts swelling up.
It turns into a Red Giant. The star keeps expanding and then starts losing its outer layers. This process forms a beautiful Planetary Nebula. At the end of the process, amidst the Planetary Nebula what remains of the star is a White Dwarf Star- the former core of the star. It’s quite like a butterfly. How is a butterfly born? It is through the process of metamorphosis in first the caterpillar eats a lot of food and gains mass.
Then it turns into a cocoon within which it goes through the process of metamorphosis. Then in the end it breaks out of the cocoon as a beautiful butterfly. Just here, the butterfly is dazzling hot and billions and trillions of years old.
What is a White Dwarf Star like?
A White Dwarf Star is tiny, very dense and a very hot star, which compared to a normal star or its former self is very minuscule- about one hundredth in size. A White Dwarf Star usually retains about half of its former mass, so it is extremely dense. It has a very thin atmosphere, about as high as a skyscraper, made up of Hydrogen and sometimes Helium gas.
The surface is made up of a thick layer of hot-burning Helium. Underneath this layer, the interior of the star is made up of heavier elements like Oxygen and Carbon. A fascinating idea is that the core of these stars could very well be a gigantic, hot diamond almost the size of the Earth.
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The Perpetual Light
White Dwarf Stars are considered much more stable than normal stars because they are extremely hot and they lose that heat and energy through a stupendously slow and inefficient process of thermal radiation. This means that they have a lot of energy that they lose as heat and light very slowly and keep shining for a very long time.
At the end of this process of dissipation of heat, the White Dwarf Stars would run out of fuel and have no more energy or light. Then they would turn into a cold and dark sphere and become what we call a Black Dwarf Star! But this would be so far off into the future that we often consider White Dwarf Stars to be the last lights of the Universe. When every other star would have died and every source of light would have vanished, it would be the White Dwarf Stars giving off the last light in the void as the last cinders in the dark and cold Universe.