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The Creation of Stars and Galaxies

13.7- 4.6 billion years ago


In the first moments after the Big Bang, the universe was extremely hot and dense. As it cooled, conditions gave rise to the building blocks of matter, quarks and electrons. A few millionths of a second later, quarks aggregated to produce protons and neutrons and in minutes these protons and neutrons combined into nuclei. As the universe continued to expand and cool, things slowed down and it took 380,000 years before atoms were formed when electrons were trapped in orbits around nuclei. These atoms were mainly helium and hydrogen, still the most common elements in existence. In the following  half-billion years, clumps of gas collapsed enough to form the first stars and galaxies. In the hearts of these stars elements like iron, carbon and oxygen are produced which are then seeded throughout the universe following explosions called supernovae. A little after 9 billion years after the Big Bang, our solar system was born. We are currently finding out more about the invisible as well as the visible universe, through agencies like NASA (National Aeronautics and Space Administration) and CERN ( European Organisation for Nuclear Research) who investigate phenomena like dark matter which does not emit any electromagnetic radiation and dark energy, comprising a huge part of the universe that we can only detect through its effects.

The Formation of the Solar System

4.6 Billion years ago


Our Solar System is part of the Milky Way Galaxy that contains billions of other stars. Our Sun is thought to be a third generation star created from the materials from two previous generations of stars which had reached the end of their lives and exploded sending their material out into the universe. About 4.6 billion years ago the solar system began to form within a molecular cloud, a concentration of interstellar dust and hydrogen gas. The cloud contracted under its own gravity and our proto-Sun formed in the hot dense centre. The remainder of the cloud formed a swirling disk called the solar nebula. It was within this solar nebula that beginnings of planets were born as dust and ice particles came together in a process called “accretion”. These planetesimals continued to grow, their gravity coming to influence each other’s motions causing more collisions and accretion and so creating proto-planets. This continued until there were only four large bodies in the inner solar system, Mercury, Venus, Earth and Mars. In the cold outer nebula much larger proto-planets formed, Jupiter, Saturn, Uranus, and Neptune. Our Moon was formed shortly after the formation of the Earth; the Earth was hit by an object half its size which disintegrated along with the outer layers of the Earth. The debris from this formed a ring around the Earth which accreted, clumped together, to form the Moon.