CAN STAR FIND PEACE?


A major problem arose in 1925 when an extraordinary star was discovered. Although it was as massive as Sun, it was only as big as the Earth! This meant that the average density of the star was about 10^6 g.cm^-3 (the mean density of the Sun is only a little more than that of water). The difficulty posed by such a dense star was the following. What will happen to such a star when nuclear energy generation at its center stops? Since the star will no longer produce heat, there will be no force to oppose gravity. What will be the end state of such a star?

Surprisingly, the resolution of this problem came from the newly emerging Quantum Physics. In 1926, R. H. Fowler at Cambridge University argued that the star will collapse and collapse till it reaches a density where a new quantum mechanical force provides support against gravity, and the star will at last find peace. This quantum pressure is due to the electrons and arises due to the combination effect of Heisenberg`s principle of Uncertainty and Pauli Exclusion Principle. Soon, Subrahmanyan Chandrasekher, a student at presidency college in madras developed Folwer`s idea into a proper theory of such quantum stars, which had come to be known as White Dwarfs. And thus it appeared to be established that all  stars will ultimately find ultimate peace as White Dwarfs.

This sense of security was shattered in l930, when Chandrasekhar discovered that such white dwarfs cannot be more massive than 1.4 times the mass on the Sun. This raised an embarrassing quesuon. What will happen to stars that are more massive than 1.4M ☉ ? Chandrasemar' S discovery implied that all such stars will collapse indefinitely and become singularities-regions of spacetime of zero volumc and infinite density.



Also see -
https://forastrophysicist.blogspot.com/2019/08/what-are-star.html?m=1

#Ankistar

Comments

Post a Comment

Popular posts from this blog

What You Observe Depends On How You Observe It.

Image
Suppose you lose your baseball in the woods, and you and your friend decide to look for it. You know that either you will find it, or your friend will (or it will remain lost). Assuming the ball hasn’t been damaged, it won’t be the case that you and your friend each find half of the ball, or that you both find the ball in different locations. There is only one ball, and it has an exact location, even if you don’t know where it is. It can only be found once, and only by one of you. A wave behaves differently, however. Suppose the ball is dropped into the center of a pond, and you and your friend stand on the shore to look for the wave. You can be on one side of the pond, your friend on the other side, and you can both see the wave wash upon the shore. You can even both see the wave wash ashore at the same time, because part of the wave is near you, while another part is near your friend. This is a fundamental difference between particles and waves. Particles are local, with a
Read more

Neutron Star

Image
In 1932, the neutron was discovered. As mentioned above, two years later, Walter Baade and Fritz Zwicky at the California Institute of Technology hypothesized stars consisting essentially of neutrons. The idea was that if one compresses a star to a density of 10^14 g cm^-3-the density of the nuclei of atoms we are familiar with then the repulsive force between the neutrons. practically touching one another. would prevent any further compression, and the star will be stable. It is just like packing a football with ball bearings; when the ball is jam-packed. it will be quite incompressible. This hypothesis led physicists to the conclusion that even stars more massive than 1.4M ☉   could find ultimate peace. not as white dwarfs but as neutron stars. A density of 10^14 g cm^-3 implies that such stars would be incredibly small, with a radius of mere 10 kilometres! So it appeared that all stars will find peace after all, either as white dwarfs or neutron stars, but this turned out to
Read more