Most comprehensive map of the universe yet could pinpoint dark matter

The map describes galaxy concentrations in our nearby sky, with our Milky Way marked by a cross (Image: University of Waterloo)

Astrophysicists from the University of Waterloo have compiled the most comprehensive 3D map of our cosmic surroundings to date. The map describes how ordinary matter is distributed in space up to a distance of about a billion light-years away from us. This survey will help scientists better understand the distribution of dark matter and explain why, to some extent, galaxies are moving erratically with respect to us.

The cosmological principle states that the matter is distributed homogeneously across the universe when seen on a large enough scale. This, however, doesn’t mean that the density of the universe is the same at each and every point in space: if that were the case, there would be no galaxies, stars, or planet Earth to speak of.

Rather, what we see are variations that occur with no set pattern, influenced by the gravitational pull of both ordinary and dark matter and forming clusters of galaxies in random directions relative to us. On the whole the fluctuations tend to average out, but in our cosmic neighborhood we still see significant variations.

Professor Mike Hudson and team have created the most comprehensive map of the universe yet, describing the distribution of galaxies in all directions, up to a billion light years out. This is a staggering distance: for reference, our own Milky Way is approximately 100,000 light years across.

As expected, the map reveals random concentrations of galaxies across the universe, with no particular pattern. Regions featuring high concentrations of galaxies are shown in white and red, while regions with fewer galaxies are in dark blue. The small red area is the Shapley Supercluster, 650 million light years away from us, the largest collection of galaxies in the nearby sky.

The survey also maps the so-called peculiar velocity of our surrounding galaxies, which is the component to the relative motion of galaxies that cannot be explained by the expansion of the universe alone, and which could be attributed to the varying concentrations of both ordinary and dark matter.

Hudson and team believe that, using this data, we could obtain a bird’s eye view of how dark matter is distributed across a very large portion of space. To help with that, the scientists are now working on getting even more detailed samples of peculiar velocities to enhance the map’s resolution.

The data appears in a recent issue of the journal Monthly Notices of the Royal Astronomical Society.

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