UNIVERSE :
The universe is simply denoted by U.The Universe consists of galaxies.
ASTRONOMY:
The Study of Celestial Objects in Universe like Stars,Planets and all is known as Astronomy.It is built on Greek root astron =
star and nomos = arrangement, order or law. Astronomy, therefore, is the
study of arrangement of stars. It is the branch of Physics that studies
celestial bodies and the Universe as a whole. ORIGIN OF THE UNIVERSE:
The Big Bang, that gigantic explosion occurred some 15 billion years
ago, is not only the beginning of our own Universe, space, matter and
time, but also the generator of all mass. This mass of interstellar
cloud of dust and gas (solar nebula) collapsed under its own gravity.
The result is, this collapse of molecular clouds vaporized the dusts and
the fireball expanded, cooled and compressed in the middle and
developed into a Protostar, leaving the rest of the gas to rotate around
it.
This cooling effect generated the most basic
elements, hydrogen and helium. In due course most of the gases orbiting
the forming star flowed inwards towards the star and became part and
parcel of it. However, the gases are rotating and therefore due to
centrifugal force some of the gases stayed away from the forming star
and formed a disc capable of building itself naturally around the
forming star. This disc gives away its energy through radiation and
cools off into metals, rocks and ice. The dust particles collide and
generate bigger particles and this process goes on till the particle
builds into the size of a small rocky boulder known as asteroids. Once
the bigger of these particles become really large enough to have its own
gravity, the growth zooms! Because of gravity, they absorb smaller
particles in their orbit and grow substantially. This process, after
millions of years got us 10 or more planets in regular habits forming
the solar system.