In Mahabharata and Ramayana there are contexts which speak of the palaces of Gods being in the heavens, and that they floated in space but as we research, it will be clear cut enough to see that.
In every civilization, Gods that people of that time worshiped came to earth from the sky. These Gods were considered to be a power source to them.
According to the world famous Russian historian Zecharia Sitchin, the Anunnaki came to the earth from planet X which according to him, is considered the twelfth planet, which he describes in his book.
The raging debate about aliens, UFOs and their existence will go on until there is solid evidence to support such claims. As humans build crafts themselves to explore and discover the galaxy n beyond.
According to the ancient alien theorists, aliens are as old as mankind and these ancient aliens had come to Earth wherein they were considered as gods by humans.