One early result of the ongoing Dark Energy Survey is the previously untold story revealed by old, giant RR Lyrae pulsating stars, which tell scientists about the region of space beyond the edge of our Milky Way. In this area nearly devoid of stars–the motion of the RR Lyrae stars hints at the presence of an enormous halo of invisible dark matter, which may provide clues to how our galaxy evolved over the last 12 billion years.
Like Earth’s Moon, two new studies have revealed insights into the vast number of ‘satellite’ galaxies around the Milky Way, including evidence that large satellite galaxies can draw their own small satellites into orbit. Using the Dark Energy Survey, Scientists have also extracted data about the halos of dark matter that surround these galaxies, as well as a prediction that our home galaxy should host an additional 100 or so very faint satellite galaxies awaiting discovery.
The universe, perhaps surprisingly, is not comprised of galaxies randomly distributed throughout space; that is, it is not very homogeneous. Instead, its galaxies are clustered into distinct structures that harbor dark matter, typically gigantic filaments separated by vast voids—the “large-scale structure (LSS),” an architecture whose discovery and mappings were pioneered by Harvard-Smithsonian Center for Astrophysics astronomers about thirty years ago.