Our Universe is full of most strange and mysterious objects. One of these objects are neutron stars. Neutron stars are among the objects having most extreme density and gravity. After black holes neutron stars are the one with most density and gravity. Neutron stars were first predicted by Swiss astronomer Fritz Zwicky in 1933, but they seemed so fantastic that they were ignored by scientists for decades. In 1933, with Walter Baade, he coined the word “supernova” and correctly predicted the existence of neutron stars. We will discuss briefly about neutron stars and how they are formed.
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| Illustration Of A Neutron Star |
What Is A Neutron Star?
In the aftermath of a supernova explosion, there is a tiny remnant called a neutron star. The density of neutron stars is unbelievably high and violent. Due to very high density, the gravity becomes extremely strong. The mass of neutron star could be equal to one, two or three suns but compressed to a diameter of only 25 kilometres. It is so dense that one cubic metre of neutron star contains the same mass as an iron cube 700 metres across. That is roughly one billion tons as massive as Mount Everest in a space of the size of a sugar cube. The gravity of a neutron star is also impressive. If you were to drop an object from 1 metre over the surface, it would hit the star in one microsecond and will accelerate up to 7.2 million kilometres per hour. The surface is super flat with the regularities of 5 mm maximum. The atmosphere of neutron star is so thin and is stretched across only 10 cm consisting of hot plasma. The temperature of the surface is about 1 million kelvin compared to 5,800 kelvin for our Sun. Now lets's look inside the neutron star. The crust is extremely hard and is most likely made of iron atom nuclei lattice with a sea of electrons flowing through them. The closer we get to the core, the more neutrons and lesser protons we will see until there is just an incredibly dense soup of indistinguishable neutrons we will see. The cores of neutron stars are of extreme weight. We are not sure what their properties are but our closest guess is super fluid neutron degenerate matter or some kind of ultra dense quark matter called as quark-gluon plasma which does not make sense in the traditional way and can only exist in ultra extreme environment found in cores of neutron stars.
A neutron star is similar to an atom core in many ways. The most important difference is that atom cores are held together by strong interaction and neutron stars by gravity. Another property of neutron stars is that they spin very fast. A young neutron star could rotate several times per second and if there is a star nearby to feed the neutron star, it could rotate up to several hundred times per second. These rapidly spinning neutron stars are called as pulsars. We call them pulsars because they emit a strong radio signal. The magnetic field of a neutron star is a trillion times more than Earth's magnetic field. The magnetic field is so strong that atoms get bent when they enter it's influence. Now, we will discuss how they are formed.
How Neutron Stars Are Formed?
A neutron star is formed from left over mass after a star dies in a supernova explosion. To know how a neutron star is formed, we have to know about the death of a star. The life of a star is dominated by two forces being in balance, it's own gravity and the radiation pressure of it's fusion reaction. In core of the stars hydrogen is fused into helium by a process known as nuclear fusion. The gravity keeps on pulling the star inward on itself but the radiation released from nuclear fusion acts as anti-gravity and keeps the star from collapsing on itself. As time progresses heavy elements began to form in the core. The helium formed in the core is then fused into heavier elements until it reaches iron. No more higher elements can be fused from iron so the fusion stops and radiation pressure drops rapidly. The star is no longer in balance. If it's core mass exceeds 1.4 solar masses, a catastrophic collapse takes place (If the star is more massive, then the result is a black hole). The outer part of core reaches velocities up to 70,000 kilometres per second as it collapses towards the center of the star. Now only the fundamental forces inside an atom are left to fight the gravitational collapse. The quantum mechanical repulsion of electrons is overcome and electrons and protons fuse into neutrons act as densely as atomic nucleus.The outer layers are ejected into space by a violent supernova explosion. Now, we have a neutron star left.
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