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Neutrinos and Their Role in Death of a Star



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While researching the mechanisms involved in the process of Core-Collapse Supernovas aka Type-II Supernovas, a team of researchers from IIT Guwahati, in collaboration with Max Planck Institute, Germany; North Western University, Illinois, USA and University of California, Berkley, USA, has come up with new observations on how Neutrinos play a vital role in the death of massively large stars.

 

Birth of a Star

  • Galaxies in our Universe contain humongous amounts of gas and dust particles which roam freely in their regions between the stars.

  • Molecular Clouds are the guilds of gas and dust particles which reside in the space between the stars called Interstellar Medium. Molecular clouds comprise of atoms, molecules and dust.

  • In the Interstellar Medium, the size of molecular clouds is very very big, even thousands of times heavier than our Sun.

  • Since the volume of these clouds exceeds even the volume of our Solar System, the particles within these clouds constantly move here and there. In this process, they strike each other and experience turbulence.

  • There comes a time when these particles start to pile up to a high level and start to collapse due to the pull from their own gravity.

  • This collapse results in the initiation of a dense accumulation of the dust and gasses at one place which gradually increases the temperature and this lays the foundation of a Star.

  • After millions of years of accumulation, compaction and surge in temperature, a Star is born, which shines like the other stars we see in the night sky.

 

Death of a Star

  • All the stars burn nuclear fuel in their core region to produce energy.

  • The heat generated through this process generates internal pressure which prevents the star from collapsing in itself due to its own gravity.

  • After a certain age, the nuclear fuel within these stars dries up and the force acting against the gravity finally succumbs. This results in the collapse of a star within its own core.

  • The process of collapse is so sudden that it generates shock waves and blasts off the star. Due to this extremely high-intensity blast, the star throws away its constituent particles.

  • In Astrophysics, this blast is known as Supernova.

  • When Supernova occurs in stars that are more than eight times as huge as the Sun, the blast is accompanied by inner material of the collapsing star and this is known as Core-Collapse Supernova or Tier-II Supernova.

  • The Tier-II Supernova can even result in the formation of a Black Hole or a Neutron Star.

 

Neutrinos

  • When a star collapses, a supernova is created which basically is a massive explosion releasing tremendous amounts of energy.

  • The energy from this supernova is carried from the core to the outer space by tiny particles with no charge called Neutrinos.

  • The Neutrinos are basically subatomic particles which are similar to an electron but have a very little or no charge at all.

  • These are one of the most abundant particles in the universe as they have very little interaction with the matter which makes them difficult to detect.

  • Neutrino is considered as a fundamental particle which is one of the basic building blocks of the universe and cant be broken down any further.

  • As neutrinos are far away in the universe and are so small that they can't be seen by a naked eye, there is very little information about their properties and behaviour.

Flavours of Neutrinos

The Neutrinos are classified on basis of the partner particles which are also the fundamental particles of the universe.

  1. Electron-Neutrinos (associated with Electron particles)

  2. Tau-Neutrinos (associated with Tau particles)

  3. Muon-Neutrinos (associated with Muon particles)

 

Oscillations related to Neutrinos

  • Neutrino Oscillations: When a Star spews out Neutrinos during a Supernova, the Neutrinos undergo multiple processes and change flavours in a process known as Neutrino Oscillations.

  • Collective-Neutrino Oscillations: During the Supernova, several Neutrino Oscillations are happening simultaneously over different energies, and are termed as Collective-Neutrino Oscillations.

  • Fast Oscillations: When one allows the neutrinos to evolve in angular symmetry, the whole process can happen at a nano-scale time scale, which is termed as Fast Oscillation.

 

The Findings of the Team and the Implications


  • Till now, to understand the neutrino behaviour, the models of this process were based on two-flavour models which used to take into account asymmetry between electron neutrino and the corresponding anti-neutrino.

  • The research paper published by a team from IIT Guwahati called Physical Review Letters, has claimed through its findings that a three-flavour model is mandatory to predict the dynamics of a Supernova through Neutrino Studies.