Our Milky Way and its neighboring galaxies are on the move. The whole Local Group of more than 50 galaxies is being tugged in one direction by, astronomers presume, the gravity of some enormous unseen object. Now, an international team believes they’ve found the culprit: a nearby supercluster– a collection of many hundreds of galaxies– that has never before been noticed because the gas, dust, and stars of our own Milky Way are blocking the view.
Earlier studies of the Local Group’s motion led to predictions that there was something lurking beyond the Milky Way. Surveys of galaxies in the constellation Vela, through which the plane of our galaxy passes, also suggested there was a higher-than-normal density of galaxies in the area. The team, using the 10-meter South African Large Telescope in Sutherland and the 3.9-meter Anglo-Australian Telescope in Siding Spring, measured the redshifts of 4500 galaxies in Vela, either side of the obscuring band of the Milky Way, and confirmed recently in the Monthly Notices of the Royal Astronomical Society that there is an overdensity of galaxies in that direction at a distance of 800 million light-years.
That means our cosmic neighborhood is home to another giant structure, slightly further away than the Shapley Supercluster– previously thought to be the local giant. And thanks to the gravity of the newly named Vela Supercluster, we’re moving towards it at a cracking 50 kilometers per second. But there is no cause for alarm: At that speed, it will take us 5 trillion years to get there.