The Event is shown to be an evolutionary process for the aliens that will endanger humans. It is possible that when the aliens lived on earth, they had to find another planet or else be endangered by the human evolution which could have been why most of the Homo genus have died out dozens of thousands of years ago.
It used to be located in the real life Sculptor Galaxy 11 million lightyears from the Solar System which is currently under an intense star formation. As of the episode "Arrival", it is currently located in between Earth and the moon.
Composition and GeologyEdit
It is possible that it has a composition similar to Earth. The aliens can breathe easily on both planets so it could have a presence of oxygen. There were clouds shown on the top half of the planet and there is barely any water. The only water is shown to be on the top left of the planet.
It is shown to be ravaged by volcanoes on the bottom half of the planet. It is a small planet about the size of Mars.
As of "Arrival", it is home to over 2.5 billion non humans.