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What is White Dwarf? How can we find them?

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What is White Dwarf ?

In universe there are billion of star , every star lives because of nuclear fusion. Mostly fusion happens in core of star but sometimes that it also happened in place near core called shells. 

If somewhere a star take birth so somewhere a star will be dead. Death of star depends on its mass. Star which have huge mass will be form as neutron star or black hole after death but which have less mass will be form as white ball who shines for trillion of years they are called White Dwarf. 

Death of Star:

As star grow old fusion will happen in different areas of star and different materials formed in this process this is known as Stellar Evolution . But every star has its time , when it's gravitational force is not upto the level to continue nuclear fusion in star which causes to start of process of dying a star. Since there is no external force (as fusion stops) so star will shrink because of it's gravitational force but it shines as material inside it is very hot. White dwarf still carries great mass like 1.4 solar masses that is called ChandraShekhar Limit and size of white dwarf is same as earth, because of it's small size and shine looks white in color it is called White Dwarf.


Ways to find White Dwarf:

Because of smaller size and less light to find out object like this is not easy but scientist have two ways to find out:

1- Note the strange motion ( slight back and forth motion ) of companion star:

Companion star do slight back and forth motion because of hugs gravity of white dwarf and if we see reflected light from the object with the help of telescope then it'll be white dwarf other wise it'll be a black hole.

A bright star we see in sky is SIRIUS has also white dwarf neighbour called SIRIUS B.



2- Search white dwarf star with the help of planetary nebula:

when fusion stops in core of star , helium present in it's shell start burning called helium shell flash because of helium burns a shockwave is generated called thermal flash , release matter of star in space (this scene looks beautiful) called planetary nebula , so when we see a nebula a white dwarf will present in middle of it.


White Dwarf size equal like earth still they contain 1/2 mass of star that makes it very dense means if you take 1 teaspoon of matter of it it'll be equal to car's mass. It's surface gravity 1 lakh times more than earths, (if you land here you'll be crushed already). So don't think about it :).


Can we find a habitable planet near it?

🤔🤔...Yeah may be but with certain condition. The distance between sun and earth is nearly 15 crore km but if we find a habitable planet near white dwarf distance will be between them is 1 to 3 crore km. But most of times if planet is too close to white dwarf then it'll be tiddly locked means it'll not orbit in it's own axis and in that case front side which will facing toward star will be too hot and back side will be too cold. So only middle portion is only place where life can be found.

White dwarf are hotter object in universe because heat trap inside it and can only be emit through radiation, but because of empty space in universe this process took trillion of years that why scientist called white dwarf last hope for life.

When light and heat ends in white dwarf that will be last stage of star called Black dwarf but it still contains huge mass and they can achieve absolute zero temperature and they'll be most cooler object in universe.



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