Scientists Discover Huge 'Extragalactic Structure' in Hidden Region of Space

Scientists have discovered a huge "extragalactic structure" hidden behind the Milky Way in a mysterious area of the sky known as the "zone of avoidance" because it is obscured by our own galaxy's opaque bulge, according to a new preprint study. Motherboard reports: The discovery of the structure, which appears to be a large galaxy cluster, helps to fill in this shadowy part of our cosmic map, which may as well be labeled "here be space dragons" because it is so unclear what exists there. The star stuff that makes up our galaxy, the Milky Way, is distributed inside a thin plane that orbits around a central bulge that contains a supermassive black hole. The galactic plane and bulge are packed with stars, dust, and gas that block our view of whatever is on the other side. Though scientists have been able to use different wavelengths to peer through the zone of avoidance (ZoA), a region that obscures 10 to 20 percent of the sky, most of this region still remains out of view. Now, a team led by Daniela Galdeano, an astronomer at the National University of San Juan in Argentina, report the discovery of "a new galaxy cluster, VVVGCl-B J181435-381432, behind the Milky Way bulge," which helps to complete "the picture of the large scale structure in this still little explored area of the sky," according to a study posted this week on the preprint server arxiv. [...] Galdeano and her colleagues were able to spot this cluster within the ZoA using the VVV Survey, a project that scans the Milky Way bulge at infrared wavelengths using the European Southern Observatory's Visible and Infrared Survey Telescope for Astronomy (VISTA) in Paranal, Chile. Whereas the galactic plane blocks out almost all visible light in the zone, longer wavelengths of light, including in the infrared band, are able to travel through the Milky Way's haze to reach telescopes on Earth. To zoom in on the tantalizing region, the researchers used a near-infrared instrument called FLAMINGOS-2, which is on the Gemini South telescope in Chile, to identify measurements called "redshifts" that can be used to estimate the distance and velocities of its objects in space. The results exposed new details about five galaxies some three billion light years away, which the researchers think are part of a much bigger cluster. The team estimated that the cluster contains about 58 galaxies, but it will take more observations to be sure of its mass and contents.

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