The universe was formed after the Big Bang, astronomers managed to explain the concept related to the Big Bang, but some questions still remain unresolved.
We know about the earliest times, when the universe was in a much denser state. It then turned into a dense, hot soup of ionized gas.
At that time, the first electron and proton combined to form the first neutral atom.
Then, as the universe cooled, the early stars were formed. These stars spread light throughout the universe. They form the galaxies we know today as stardust.
These mainly include - stars, black holes, cosmic dust and other mysterious substances commonly known as dark matter.
The size and nature of galaxies vary. Some galaxies are spiral shaped and some are irregular and elliptical.
Some recent astronomical explorations have also revealed a needle-shaped galaxy.
But the question arises that who came first, the stars or the galaxy?
Stars first formed after the Big Bang and later merged into the Milky Way or did galaxies form with stars?
The question is something like this - did the chicken come first or the egg?
But in reality it is nothing like that. According to the best scientific estimates, about 200 million years after the beginning of the universe, the first objects began to emerge from the fireball of the Big Bang.
These objects had to be so massive that their self-gravity was strong enough to be crushed against the force of the hot gas pushing them outward.
It took a relatively large mass of gravity to shrink the gas cloud shortly after the Big Bang because the gas in the Big Bang was so hot.
As a result, the first objects in the universe – commonly known as 'mini-halos' – had a mass of about one million suns, which is currently about 0.001% of the mass of a larger galaxy.
It was in these objects – galactic fragments, if you like – that are believed to have formed the first so-called Population III stars.
Over time, the mini-halos merged to form the Milky Way and Andromeda and the other giant galaxies that populate today's universe.