Supernovae or stellar explosions play a very significant role within an interstellar medium. Each explosion, not only enriches the surrounding medium with higher mass elements, but also triggers new star formations from the expanding shock waves and explosion. In star astronomy, the term 'nova' relates to 'new'. It results in the appearance of a bright, new star in the celestial medium. The term 'supernova' was first coined in 1926, by Fritz Zwicky, a Swiss astrophysicist and astronomer. The earliest records on these outer space spectacles date back to the supernova SN 185, sighted and studied in 185 AD. Other records offer an insight into the study of the SN 1006, SN 1054 that generated the Crab Nebula, SN 1572, and SN 1604, which was the last to be observed.

What is a Supernova?

A supernova refers to a stellar explosion, or explosion of the stars. The very luminous burst of radiation is capable of hiding a whole galaxy in its shadows. It takes quite a few months before the last show of light-and-form extravagance actually fades from sight. During its lifetime, it is observed to radiate energy as much as is associated with the sun. In fact, research reveals that a single supernova is capable of emitting energy that the sun would otherwise radiate over its whole lifespan!

Supernova Explosion

During a supernova, the fading or dying star expels all of its composition. It actually takes place at the velocity of one-tenth of the speed of light. This colossal bang emits a shock wave that rocks the interstellar medium around. The remnants are expelled during this generated 'shock' and are thrown out in the form of an expanding gas-and-dust shell. A supernova may be triggered by a sudden 'turn-off' or nuclear fission that results from a sudden 'turn-on' in the energy production within. In case of an aging star, it reaches a point in time, beyond which the core ceases to generate energy that is otherwise created via nuclear fusion. This causes a sudden and abrupt gravitational collapse. The resultant black hole or neutron star re-releases potential energy, heating up and expelling the outer layers.

The triggered action culminates in the formation of a white dwarf star. This formation is the result of accumulated material from the emitted stellar explosion. The raised core temperature ripples on to generate carbon fusion, runaway nuclear fusion, and finally, complete annihilation of the star. White dwarfs thus formed also display thermonuclear explosions that result from the hydrogen content on the surface or nova. Research reveals that there are a number of solitary stars that never go through this kind of eruption. This is usually the case with stars that have a mass much below eight or nine solar masses. In this case, the stellar annihilation is characteristic of the formation of white dwarfs and the ultimate 'fizz-out'. Studies prove that on an average, an explosion is witnessed once in every 50 years, in our galaxy - the Milky Way.

Interestingly, the development of the telescope has proved, beyond its basic function of enlarging the occurrence, a boon for a better understanding of cosmological distances, maximum intensity, and the 'suggested' expansion of the universe. It generates elements heavier than oxygen, which are produced by nuclear fusion and nucleosynthesis. Post-explosion, the remnants actually survive in composition, in the form of a cloud, for nearly two centuries. The essential and gradual adiabatic expansion causes the cool-and-mix for the merger with surrounding interstellar medium.