all about supernovas

What are supernovae...?

Most of us might have heard the term " supernova ". The name itself suggest that it has something to do with light and explosion. Something really big and interesting and mysterious.



Let us first gather a basic idea : supernova is the name given to the phenomenon of explosion of supergiant huge massive stars after it has completed its lifespan.
A supernova throws out many heavy elements in all dimensions.
It is also found that supernovae emit audible sound waves before the explosion of the source star due to its own internal explosion.
The first supernova explosion was observed by the man kind in 2008.

The energy emitted by the supernovae may depend on the size and properties of the source star but the value revolves around the fourtieth power of ten (more than 10⁴³). This means it would emit energy that our own sun would emit in its entire lifetime. The brightness caused in a supernova may be observed at large distances throughout the space.

Now one may have the question in mind that whether our own sun result in a supernova or not ? The answer would be NO. Our sun does not have sufficient mass, size and energy to cause a supernova. Infact our sun would grow many times bigger than at present and gradually cool down. This is called a white dwarf. But before it become a white dwarf, due to sun's large grown shape, our earth and other planets would vapourise into the space.

It is expected that a supernova explosion occurs every second somewhere or else in the universe. This means that a galaxy like our own witnesses a supernova in every 50 years. This may sound a rare case when we talk about a period of 50 long years but we have to keep in mind that we are talking about the explosion of a huge star taking place in the space. So this rate can be considered quite often.

Now we have arrived at the point where the main question is why does some star explode to result a supernova ? Well... the answer is not simple...
There is a series of prosesses taking place through the surface to the depth of the stars. These complicated prosesses starts taking place at the very beginning of the star's existense and carry in till the event of its explosion. So we can say that supernova is the conclusion of the star's life.  Therefore a supernova is the event of the death of a giant and powerful star.

Now you may ask what actually causes the explosion ...? Fortunately this time there's a straight forward answer. The fusion or fission inside the star is responsible for it. An iron core is built up in the the centre of the star due to fusion. The nuclei of the iron group elements are the most tightly bound, so no more energy can be expected from nuclear fusion after it has operated for a period of millions of years. During this period, iron group elements has absorbed a large amount of energy. The star's own gravitation causes increase in temperature which in turn facilates the fusion of iron at the core. If the temperature is high enough , it'll be absorbed and there will be a reheat and restart of the process of collapse of the core. This process is repeated millions and millions of times during the whole lifetime of the star. The fusion of electrons and protons gives neutrinos which serves as the carrier of matter in all dimensions during the explosion.


Classification of supernovae :


Supernovae are classified and reclassified into two categories and and their sub-categories on the basis of the properties of their light spectrum and the properties of the source star and also on their shapes of light curves.

Classification as type-1 And type-2 supernovae : ...


Type-1 supernovae :

Type-1 supernovae are associated with the stars that are with low mass and low energy. This type of supernovae requires a binary system of stars where one is insufficient to cause supernova alone. Here one star is in the end of its lifespan and is in the state called white dwarf.

Here the hydrogen is not seen in its light spectrum. One star accumulates matter from the neighbouring ending star. As the gas and matter of the companion star is compressed, there starts a runaway nuclear reaction which eventually leads to a supernova explosion.

This type of supernovae have light curves exhibiting sharp maxima and then die gradually. This type of supernova occur in elliptical galaxies like our own.

Type-1 supernovae are sub-categorised as 1a, 1b and 1c supernovae :

Type-1a : if they have strong silicon lines in their light spectrum.

Type-1b : if they have strong helium lines in their light spectrum.

Type-1c : if they don't have any of the above.

Type 1b and 1c involves collapse of the core like type-2 supernovae.

Type-2 supernovae :

In type-2 supernovae, the stars run out of the nuclear fuel like hydrogen and helium. Here the collapse of the core of the star due to its own gravity is responsible for the explosion. This kind of supernovae are associated with one single giant massive star and unlike type-1 , no binary system of stars is needed. The star gradually runs out of hydrogen and helium after millions of years of its lifespan at the end but is left with a huge amount of mass and immense pressure. Here the carbon fission takes place inside the star due to the immense pressure. Gradually the star becomes layered, becoming more and more denser as we move towards the core of the star. Heavier elements occur at the core with immense pressure. Once the core crosses the chandrasekher limit, it starts imploding and the process of explosion begins. At last, after all the heavy elements are thrown away, a neutron star is left behind.

Type-2 supernovae are sub-categorised on the basis of their light curves as type-2L and type-2P :


Type-2L : this kind of supernovae decline uniformly after the explosion.

Type-2P : in this case, the light lasts for linger period of time.




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