The universe is ever expanding just like our knowledge of how the universe came to be, the big bang is the leading theory on how the universe started, it started with a small singularity that happened more than 13.8 billion years ago, which ended up building the universe we know today, because we were not around then and don’t have the current technology to know what accurately happened with mathematical equations, formulas and models.
It first started with a singularity, which released particles called protons, neutrons and electrons, NASA believes that this early state of the universe would have been impossible to look at as light could not be carried through these particles "The free electrons would have caused light (photons) to scatter the way sunlight scatters from the water droplets in clouds," NASA stated. Over time, however, the free electrons met up with nuclei and created neutral atoms.
This allowed light to shine through about 380,000 years after the Big Bang, this ‘afterglow’ of the big bang is more properly known as cosmic microwave background or CMB. It was first predicted by Ralph Alpher and other scientists in 1948 but was found only by accident almost 20 years later. With these particles, formed elements, all 92 natural elements found on earth, including the ones that make our bodies were formed, these elements were formed from star fusion reactions, when they can release gases.
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Small stars like a sun create lighter atoms through fusion reactions. Larger stars with heavier cores make the heavier elements up to iron. The rest are forged by exploding supernova or the death of a large star. Hydrogen and helium being the easiter elements to form fill most of our universe with hydrogen filling 75% of the universe and helium with 23%, and the rest making up 2%. These constituents were not evenly distributed throughout distance, and under the influence of gravity they begin to "cluster " to form more concentrated volume. Evidence of this uneven distribution can be found in the anisotropy detected in the Cosmic Background Actinotherapy (CMB) by the COBE satellite in the early 90's. These clumps would eventually form galaxies and aces.
Yet despite all its awe-inspiring brilliance, the sun's formation follows a specific pattern of cosmic happenstance. Like so many things in the universe, stars begin very small -- mere particles in vast clouds of dust and gas. Far from active stars, these nebulae remain cold and monotonous for ages. Then, like some sleepy little town in a biker movie, everything stirs up when a newcomer speed through. This disturbance might take the form of a streaking comet or the shockwave from a distant supernova.
As the resulting force moves though the cloud, particles collide and begin to form clumps. Individually, a clump attains more mass and therefore a stronger gravitational pull, attracting even more particles from the surrounding cloud. As more matter falls into the clump, its centre grows denser and hotter. Over the course of a million years, the clump grows into a small, dense body called a protostar. It continues to draw in even more gas and grows even hotter.
When the protostar becomes hot enough (7 million kelvins), its hydrogen atoms begin to fuse, producing helium and an outflow of energy in the process. We call this atomic reaction nuclear fusion. However, the outward push of its fusion energy is still weaker than the inward pull of gravity at this point in the star's life. Think of it like a struggling business that still costs more to operate than it makes. Material continues to flow into the protostar, providing increased mass and heat. Finally, after millions of years, some of these struggling stars reach the tipping point. If enough mass (0.1 solar mass) collapses into the protostar, a bipolar flow occurs.
Two massive gas jets erupt from the protostar and blast the remaining gas and dust clear away from its fiery surface. At this point, the young star stabilizes and, like a business that finally becomes lucrative, it reaches the point where its output exceeds its intake. The outward pressure from hydrogen fusion now counteracts gravity's inward pull. It is now a main sequence star and will remains so until it burns through all its fuel.
What is the life p of a star? It all depends on its mass. A star the size of our sun takes roughly 50 million years to reach main sequence and maintains that level for approximately 10 billion years [source: NASA]. Astronomers classify the sun as a g-type main sequence star - the "g" indicates the sun's temperature and colour. Larger, brighter stars burn out far faster, however. Wolf-Rayet stars boast masses at least 20 times that of the sun and burn 4.5 times as hot yet go supernova within a few million years of reaching main sequence [source: NASA].
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