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Astronomy is the science that studies space: its origin, evolution, composition and the phenomena that take place in it.
Humans have studied space to better understand natural phenomena that seemed elusive to them. Even today, the Universe surrounding the Earth is unknown, as it is only recently that powerful enough instruments have been developed, thus making it possible to see beyond the dimensions of our solar system.
Space is defined as the region starting at approximately 100 km above sea level. Beyond this altitude, the Earth's atmosphere is no longer dense enough for aeroplanes to fly and objects can be placed in orbit around Earth. The phenomena taking place there are known as astronomical phenomena. These include the movement of different stars, the explanation of eclipses, or the formation of galaxies.