Question

The Big Bang took place some 20 billion years ago. How long after that the first stars began to form?
A. 1 billion years
B. 5 million years
C. 1 million years
D. 4 billion years

Answer 1

Hint: Universe is all the matter and energy that exists or ever existed in our knowledge. The study of the universe is called cosmology. The scientists who study cosmology are called cosmologists.

Complete answer:
 The universe has been created or started existing about 12 - 15 billion years ago, due to the big bang as we know. According to the theory that has ever been thought of, the Big bang was a gigantic explosion which created all of the mass and the energy in the universe in less than a second.

The big bang was extremely hot. It was around $${10}^{27}{}^{\circ }C$$. The big bang thought it was an explosion but the form of the universe was not created immediately. It took billions of years to form the universe as we see it today or the formation of stars wasn’t immediate.
The steps of the forming of the universe can be divided in to the following parts:
The big bang: it took only $${10}^{-43}s$$ to take place in a portion where the universe expanded vastly and all of space and time was created at that moment.
The shaping of the universe: after the big bang occurred the universe took shape in a matter of microseconds. In this time the basic forces become distinct.
Formation of the basic elements: In a few seconds the protons neutrons come together to form nuclei and form light elements like hydrogen, helium etc.
The era radiation: The radiation or the waves mainly electromagnetic in nature started bombarding the universe after a span of 10,000 years.
Beginning of the dominance of matter: At this stage the waves converted into matter and formed stable atoms combining with the nuclei, this era started after a span of 300,000-500,000years.
Birth of stars and galaxies: In this era the first star was formed as gravity takes over then a group of stars formed a galaxy. This span started at 3-4 billion years marks

After this stage our own solar system was formed at a mark of 5 billion years.So, from the stages we can see that the early star was created at an age of 4 billion years.

Hence, option (D) is the correct answer.

Note: To remember the exact birth mark of a star it is advised to remember the birthmark of our sun. The sun was created 5 billion years ago and the first star formed 1 billion years before that. The word universe describes all of the things that exist. The universe is too vast, in measure of light years; it will take like 15 billion years to reach the other end of it as far as we have interpreted from our knowledge.