Dark matter bridge in cosmic neighborhood | Science Wire | EarthSky
Astronomers led by Noam Libeskind at the Leibniz Institute for Astrophysics Potsdam this week (July 14, 2015) announced they’ve built a detailed map of how nearby galaxies move. In it, they say, they’ve discovered a bridge of dark matter stretching from our Local Group all the way to the Virgo cluster – a huge cluster of some 2,000 galaxies roughly 50 million light-years away. The astronomers say the dark matter bridge is bound on either side by vast bubbles completely devoid of galaxies. They say this bridge and these voids will help them understand a 40-year-old problem regarding the curious distribution of dwarf galaxies.
Dwarf galaxies are often found swarming around larger galaxies like our own Milky Way. Since they are dim, they are hard to detect, and are thus we know dwarf galaxies almost exclusively in our cosmic neighborhood.
One of their most fascinating aspects is that, near the Milky Way and at least two of our closest neighboring galxies – the Andromeda and Centaurus A galaxies – these satellites don’t just fly around randomly. Instead, they’re compressed on to vast, flat, possibly spinning, planes.
Most modern cosmologists rely on a theory known as the Cold Dark Matter model to understand the universe forms galaxies. But this model does not explain this feature of dwarf galaxies, which are thus an unexplained challenge to the theory.
The dark matter bridge might help explain them. The dwarf galaxies “echo the geometry of structure on much greater scales,” the astronomer said in a July 14 statement. ...
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