Sanjeeth Baliga, TE EXTC
BIG BANG!!That’s what led to the birth of our universe about 14 billion years ago.
Then began a process known as inflation of space according to which the universe is
continuously expanding .But then, there arise two million-dollar questions .What
observations made by the astronomers led them to conclude that the universe is
expanding? And how did we come to know what the billions of galaxies in the
universe looked like shortly after their formation? All such questions are answered by
some of the most mysterious objects in space known as ‘quasi-stellar’ objects or
simply quasars.
A quasar is a very energetic and distant active galactic nucleus. It is extremely
luminous and emits a lot of electromagnetic energy, including radio waves, ultraviolet
radiations and even gamma rays.
Most galaxies have a supermassive black hole at their centre or nucleus. Such a black
hole is the largest of its kind and it’s mass is of the order of thousands to billions of
solar masses. This supermassive black hole pulls matter within its event horizon
spirally inward towards its centre. This process is known as accretion. During this
process, gravitational and frictional forces compress and raise the temperature of
matter causing the emission of electromagnetic radiation .Now in case of some
galactic nuclei, the emission of radiation is exceptionally high. These nuclei appear as
highly luminous objects in space. These luminous objects are nothing but quasars
.And the galaxies which host quasars are the active galaxies .They are generally newly
born galaxies.
A quasar’s luminosity is about 4 trillion times that of our sun or at least about 100
times that of the total light of giant galaxies like our milky way. It has been observed
that the light emitted by quasars have wavelengths which move towards the red end
of the spectrum and hence they exhibit ‘red shift’ .According to Doppler’s effect any
body which exhibits red shift is continuously moving away from the earth .This leads
us to the conclusion that galaxies hosting quasars are receding away from us which
explains the inflation of space. Another notable fact is that the red shift indicates that