If you're looking for anime similar to Voices of a Distant Star, you might like these titles. All recommendations are made by Anime-Planet users like you!
The story follows a "time researcher" and a group of children in a depopulated world that finds itself stuck in time. In order to save humanity, some of the characters are chosen to travel to the future (depicted in the anime), and others to the past (depicted in the manga), while those who are deemed unsuitable for the technology stay in the present (depicted in the novel.)
Both ova's are a short story about what the future is like for a group of girls sent far away to fight for Earth in their own ways. A cell phone connects both of the main girls from each ova to their past lives as well as their romantic feelings for a boy. I'm positive fans of either will love the other.
It's been a thousand years since the Gauna, a strange alien race with no known method of communication, destroyed the solar system. A portion of humanity managed to escape using enormous "seed ships" like the Sidonia, which have allowed them to maintain the population while drifting through space. Nagate Tanikaze is a young man who has been raised deep in the bowels of the ship. When he goes into training to pilot the huge robotic weapons known as Gardes, Nagate is entrusted with piloting the legendary unit known as Tsugumori. Nagate and his fellow pilots put their lives on the line against the Gauna, in the ultimate battle for the survival of humanity.
These two do have some common elements. Mecha, aliens, 3D CGI, and giant spaceships. Still, Voices accomplishes more character and story wise in 25 minutes than Sidonia accomplishes in 12 episodes. But where Voices is extremely focused on the characters, Sidonia is more focused on the world they live in. Both are beautifully animated, but one is about a future with giant spaceships and mecha, the other is about the people who live in that future.