An immense wall of galaxies, stretching over 380 million light-years, is hiding beyond the far side of the Milky Way.
Dubbed the Vela supercluster, this galactic horde sits about 800 million light-years away in the constellation Vela, researchers report online November 8 in Monthly Notices of the Royal Astronomical Society Letters. Despite its size and relative proximity, Vela has gone unnoticed because it is largely obscured by our own galaxy.
Superclusters — assemblages of groups of galaxies — are among the largest known structures in the universe. Following up on earlier hints that an uncharted supercluster might lurk nearby, Renée Kraan-Korteweg, an astronomer at the University of Cape Town in South Africa, and colleagues scoured a patch of sky bisected by a wall of stars that is part of the Milky Way. Using telescopes in South Africa and Australia, they measured distances to 4,432 galaxies and found that many, to the north and south of the wall, appear to be clumped together.
Vela could help solve a long-standing mystery. The Milky Way and dozens of other galaxies in the immediate neighborhood move together through space. Gravity from known superclusters can account for some of that motion, but not all of it. Astronomers don’t yet know the mass — and hence the gravitational influence — of Vela, but it could be partly responsible for nudging us along.