A map showing the relative sizes of galaxy superclusters in the universe. Vela, recently mapped for the first time, is at the far left. (Image credit: Jérôme Léca, RSA Cosmos)

Astronomers have finally mapped out a mysterious galactic "supercluster" that has been almost completely hidden from Earth since it was discovered 10 years ago. The results reveal that the structure is far larger than we realized, and it now ranks among some of the most massive objects in the known universe .

The Vela Supercluster is a collection of at least 20 galaxy clusters, each of which contains hundreds or thousands of galaxies, all gravitationally bound into a single entity.…