The Universe

Copernicus in 1543 A.D. proposed
the heliocentric view, which states
that the Sun is the centre of the
Universe instead of the Earth.

The Origin of the Universe
Big-Bang Theoery: By E. George
lamantor . According to him, 15
billion years ago there was a big
heavenly body, made up of heavy
matters. Due to sudden explosion
(Big Bang) of this heavenly body,
normal matters came out of it. And
many celestial bodies were created
as a result of aggregation of these
normal matters. Gradually their size
increased due to continuous
accumulation of normal matter
around them. In this way, galaxies
were created. Stars were formed due
to re-explosion of these galaxies. In
course of time, the planets were also
formed in the same process.
Galaxy
A Galaxy is a large constellation of
stars in which there is a central
bulge and three rotating arms. Every
galaxy is composed of about 100
billion stars. Our own galaxy is
known as 'Mandakini ' which has
spiral shape. A group of stars known
as ' Milky Way ' seen in the night, is
a part of our galaxy. Orian Nebula is
the brightest and the coldest group
ofstars of our galaxy.
Life Cycle of a Star
Rotation of the galaxy causes the
gaseous clouds present in the
universe to become compact and due
to the gravitation the process of
nuclear fusion starts at the centre of
this gaseous mass, converting
hydrogen into helium. This process
liberates an enormous amount of
energy in the form of heat and light.
At this stage the gaseous mass
becomes a star. When star expands
to a large size the temperature of
the star at this stage also falls down,
so it appears red. This is the Red
Giant Star.
Supernova :
The helium starts
converting into carbon and carbon
into heavy metal like iron in the
core. This results in a massive
explosion in the which is known as
supernova .
Chandrasekhar Limit : If the initial
mass of the star is less than 1.4
times the mass of the sun, then it
ends its life as a white dwarf star,
which is also known as a Fossil star. White dwarf ultimately turns into a Black dwarf . The limit 1.4 of solar mass has come to be known a
Chandrasekhar Limit .
Neutron Star:
Unlike above, if the
mass of the star is much more than
the mass of the sun then it became
Neutron Star.
Black Hole:
A Neutron Star remains
contracting and, thus, mass in a
large quantity, concentrates on one
point. Such body with high density
is called Black Hole. It does not
allow anything to escape, including
the light due to which it can be
seen. It is John Wheeler who
propounded the concept of Black
Hole