what is a star and because how it from in the solar system
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Answer:
A star is a huge mass of plasma, or matter, that is held together by its own gravity. The matter consists mostly of hydrogen and helium, the most commonly found elements in the Universe. Hydrogen and helium clouds float around in space in clouds of cold gas. Every now and then a cosmic event like a galaxy collision, a supernova explosion or other disturbance will take place that causes the cloud to collapse and heat up. This forms the base of a new star.
This heating process is nothing like your normal oven. It takes millions of years and reaches massive temperatures of over 18 million degrees Fahrenheit combined with mega internal pressures. At these temperatures, hydrogen changes to helium in a nuclear fusion reaction and a star is born. Stars can be created alone, in pairs, clusters or even in entire galaxies.
The closest and most familiar star to us is the Sun. Other stars are much further away and simply appear as pin points in the sky. Stars go through various phases during their lifetimes. Depending on the temperatures at which they burn, they appear to have different colors, hence the names red, brown, orange or yellow dwarfs. When the hydrogen runs out and stars cannot burn any longer, they will change into other cosmic bodies. Smaller stars will become white dwarfs and larger stars will explode to become supernova or those illusive, mysterious black holes!
Stars form inside relatively dense concentrations of interstellar gas and dust known as molecular clouds. These regions are extremely cold (temperature about 10 to 20K, just above absolute zero). At these temperatures, gases become molecular meaning that atoms bind together. CO and H2 are the most common molecules in interstellar gas clouds. The deep cold also causes the gas to clump to high densities. When the density reaches a certain point, stars form.
Since the regions are dense, they are opaque to visible light and are known as dark nebula. Since they don't shine by optical light, we must use IR and radio telescopes to investigate them.
Star formation begins when the denser parts of the cloud core collapse under their own weight/gravity. These cores typically have masses around 104 solar masses in the form of gas and dust. The cores are denser than the outer cloud, so they collapse first. As the cores collapse they fragment into clumps around 0.1 parsecs in size and 10 to 50 solar masses in mass. These clumps then form into protostars and the whole process takes about 10 millions years.