The universe is very much mysterious, even till now after calculating tons of data we are unable to find out all of the things it contains. It is continuously expanding and a lot of stars born every day in our universe. We all know that whatever or whoever born has to die one day, and similar to living beings these stars in the universe also die at certain times or age; and when a star dies at the end of its age, it depends upon its mass. Stars with heavy mass end up like neutron stars or black holes whereas stars with low mass (i.e. at least less than 8 times than that of our sun) end up like a white dwarf star.
The density of ancient stars is very high. To our wonder, even the spoonful of their matter weighs as much as an elephant on Earth i.e. about 5.5 tons. Their mass is the same as that of the sun but their radius is just 0.1 of sun. A fusion occurring in star’s core emits heat and also exerts outward pressure but this pressure is balanced by the inward push of gravity generated due to the mass of the star.
When the hydrogen fully used up the infusion reaction, the star collapses on itself. Similarly, white dwarfs are the stars whose hydrogen used as its nuclear fuel completely vanish. It is the final evolutionary stage of the star that does not have enough mass to become a neutron star or black hole.
White star has no energy source other than the energy left during its birth. The mass of oxygen and carbon dioxide is equivalent to the sun, but the size is very much smaller, and its luminosity is also low. It is also observed that some white stars have such low luminosity that some only glow equivalent to 100 W light bulbs seen at the distance of the moon.
The white dwarf star fades and cools down as its age increases and its luminosity also fades. Its center cools down to the point that the oxygen and carbon dioxide in the center of the star starts to become crystals. Almost after 5 billion years, the white dwarf star’s core becomes crystalline just like a diamond in the sky.
The age of these types of stars is about 15 billion years. i.e. older than the current age of the universe; their outer layer will cool down to a few thousand degrees and their luminosity will fade to 1/100,000 times that of the sun. Researchers also say after formation, that the white star will remain stable and cooling down continuously and one day eventually becomes a black star. In this way in 1019 to 1020 years, the galaxies will get evaporated because their stars will escape into intergalactic space.
Example: ‘Sirius A’ (the brightest star in the night sky); ‘Sirius B’ etc.
Some Interesting White Dwarf Facts
1. ‘Alvan Clark’ discovered the first white dwarf in 1862. He was a telescope maker. “Sirius B” is the name of that white dwarf star.
2. The size of the white dwarf depends on its mass; the more the mass of the star, the smaller its size.
3. White dwarfs are very rare. We only found 8 white dwarfs in the nearest 100 solar systems. The closest known white dwarf is “Sirius B”; it is a companion “Sirius A” in the Sirius binary system.
4. The white dwarf will become a black dwarf. White dwarfs are cores of dead stars. Their temperature is decreasing as time passes and once its temperature will the same as that of space; at this stage, they will become a black dwarf. Yet, no black dwarfs are found because it takes trillion of years to cool down for white dwarfs and it is many times longer than the current age of the universe.
5. About 97% of stars in the Milky Way galaxy will become a white dwarf. The stars in a milky way including our sun will evolve one day and become a white dwarf. After that, the white dwarf will become black dwarf and our Milky Way will get disappear except for few neutron stars that may outlive the dispersion of galaxy and all-black dwarf.
6. A dwarf star’s density is so much high. It will take 8 men to lift a single teaspoon of its matter.
7. The biggest known diamond in-universe named Lucy is actually a white dwarf. It’s core containing carbon crystallized upon cooling, which leads to the formation of this giant diamond.
8. The gravity of the white dwarf is 350,000 times that of Earth. (OMG!)