Intergalactic traveler.
A Russian space traveler is called a cosmonaut.
It is a traveler.
An American space traveler is called an astronaut.
viajero
Our galaxy is called the Milky way, but the closest neighbouring galaxy is called the Andromeda galaxy.
Marcus Rauchfuss goes by Traveler.
The Milky Way galaxy is.... called the Milky Way Galaxy
Vyamonaugt
Traveler
It's called an Intergalactic collision or Interacting Galaxy. Where a galaxy is consumed, or more correctly "merges" is called galactic cannibalism.
The galaxy that contains Earth is called the Milky Way.
A dwarf galaxy