Formation of Galaxy | Origin of the Universe | Big Bang Theory

Origin of the Universe

Introduction:-

The vast vast space around us is called the universe and it includes all the bodies like distant stars, planets, satellites as well as the earth and all the matter on it. In other words, the universe, from the smallest molecules to the giant galaxies, is called the universe.

There is a lack of adequate knowledge regarding the size and extent of the universe. However, it is estimated that there are about 100 billion celestials in the universe and 100 billion stars in each. The Sun, which is the basis of life on our planet, is the only star in this universe of billions of stars. Earth on the other hand is similar to a small point in this vast space called the universe. 

Galaxy Formation and Evolution

Earth is one of the eight planets, all these planets revolve around the Sun. These billions of stars present in the universe are not evenly distributed in space. These stars occur in groups (or clusters) called galaxies. Thus, in order to study the structure of this universe, we will first discuss the galaxies, stars, planets, satellites etc. located in the universe.

Distance measuring unit in the universe

• Extremely large distances between various celestial bodies, stars and planets can be expressed in the astronomical unit Light Years and Parsec.
• The astronomical unit is defined as the average distance from the Earth to the Sun. An astronomical unit is equal to 1.5 X 10⁸ km.
• The distance traveled by light in a year is called light year. It is equal to a distance of 9.46 X 10¹² km.
• Parsec: Parsec is used in astronomy. Its length is based on trigonometric angle, an ancient method of measuring distances between stars. It tells the distance at which the radius of the Earth's orbit shifts the angle of the circle in one second. A parsec equates to a distance of about 30.86 ptometers, 3.26 light years or 30.9 trillion km.

Origin of the Universe (Galaxy formation and Evolution)

The universal theory of the origin of the universe is the Big Bang theory. It is also called the extended universe hypothesis. In 1920, Edwin Habbal testified that the universe was expanding. With the passage of time, galaxies are moving away from each other.

The expansion of the universe here means increasing the distance between galaxies. Scientists believe
is that the distance between galaxies is increasing, but observations do not prove the expansion of the sky. Hoyle proposed the permanent state concept as an alternative. According to them, the universe has always been the same, it has neither started nor end. Although the scientific community now supports the universe expansion theory, after getting many evidences regarding the expansion of the universe.

States of Big Bang Theory

Initially, all the substances from which the universe originated were located in the same place as a single atom. Whose volume was extremely low and temperature and density were infinite.
In the process of Big Bang, it caused a huge explosion in the very small ball. This type of explosion process led to a wide expansion. There is now a general consensus among astronomers about the fact that the incident of Bigbang occurred 13.7 billion years ago.

The expansion of the universe continues even today. Some energy was converted into matter due to expansion. After the explosion, a large expansion took place within a short span of one second. After this the pace of expansion slowed down. The first atom was formed within the first three minutes of the Big Bang. During the 3 million years from the Big Bang, temperatures dropped to 4500 degrees Kelvin and atomic materials were formed.

Evidence in support of the big bang theory

Evidence: -
Red shift phenomenon in relation to galaxies: If the distance of the light source increases from us, the frequency of received light will be virtual and this frequency will migrate towards the red character of the visible spectrum.
Explanation: -
Other skies are rapidly moving away from us.

Evidence: -
As the distance between galaxies increases, the red shift of its light is greater.
Explanation: -
The best explanation of this is that the whole Universe is expanding. This supports the theory that the universe may have originated with an explosion.
Evidence: -
Cosmic microwave radiation background
Explanation: -
The relatively uniform cosmic microwave radiation is a residue of energy produced immediately after the Big Bang.

Milky Way

It is a group of stars that are bound together by their own gravitational force.

Its main features are:

• It is spiral.
• Its diameter is about 100,000 light years and its size is stunning.
• It is rotating counterclockwise at its center.
• All the stars (along with the solar system as well as the Sun) revolve around the center of the galaxy.
• The star disk is quite thick at the center, representing a relatively high concentration of stars at the center of the galaxy.
• The distance of the Sun from its center is quite large (about 27000 light years).