Humans have looked at the night sky since prehistory. They knew that there were moving stars: Mercury, Venus, Mars, Jupiter and Saturn. We do not have evidence that suggests when humans first noticed this. But we do see archaeological evidence that indicates where some of our knowledge originated.
The Sumerians appear to be the first people to use constellations to recognize features in the sky (4500 BCE). The Chinese appear to be the first observers to create star charts (700 CE). Many of the constellations we use today are from the Greek and Roman mythology (about 20 CE). Many of the star names we use today are from Arabic (about 750 CE). In 1928 CE the International Astronomical Union defined the 88 current constellations. They broke the sky into regions (like states). These are the constellations we use today. There never will be any new ones.
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