Stars
Stars are heavenly bodies that, through nuclear fusions in their cores, radiate their own light. The universe is full of them, probably numbering somewhere in the trillions. However, we can only see a small fraction of them. Stars are formed from interstellar clouds made up of hydrogen and dust particles. These raw materials gather until they collapse under their own gravity. The cloud undergoes a sort of condensation, becoming more dense and hotter. At this stage, it gives off a faint glow, much like a red-hot iron poker does. Eventually, the star reaches a point where nuclear fusion can take place inside. The remaining hydrogen is combined to form helium. As this fusion takes place over millions of years, the hydrogen is used up and the star's temperature slowly rises. taisiya povaliy At some point, the star grows and cools, becoming a red giant. This is the result of a star fusing outer layers of hydrogen. Depending on its mass, one of two things will happen next. If it is a small star (~1 solar mass), the outer layers dissipate into space, leaving behind a small, hot core known as a white dwarf. Stars that are massive (~5 solar masses) are able to continue fusion and create heavier elements in their cores. This fusion results in a collapse of the core and creates a supernova, a violent event. The star appears to shine 100 times brighter for many months. After the supernova subsides, the core may remain as a neutron star. However, if there is still plenty of mass after the supernova, it will collapse further in on itself, creating a black hole. Our own Sun is a smaller star and will eventually grow into a red giant and shrink to a white dwarf. But there's no need to worry as it won't happen for another few billion years. For more information on stars, consult the following links:
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