Astronomers have mapped the universe's quasars in unprecedented detail thanks to a ream of accidental observations from the Gaia observatory. The new "3D catalog" is expected to offer researchers fresh insight into dark matter, cosmic expansion, and the distribution of material throughout the universe.
The European Space Agency's Gaia spacecraft is designed to capture precise three-dimensional images of the Milky Way. But sometimes, the observatory's billion-pixel camera captures data from outside our galaxy—namely, quasars and other galaxies. For most Gaia-related projects, these observations might be considered scrap data or noise polluting a research team's target image. But one scientist's trash is another scientist's treasure, and one international research team found the value hidden in Gaia's 6.6 million potential quasar findings.
Astronomers at New York University, Spain's Donostia International Physics Center, and Germany's Max Planck Institute for Astronomy compared Gaia's accidental quasar data with existing unWISE observations. By reprocessing WISE (Wide-field Infrared Survey Explorer survey) data to achieve improved depth and spatial resolution, unWISE researchers mapped and cataloged roughly two billion space objects. Comparing Gaia's findings with the unWISE catalog allowed the team to reduce the number of "contaminants" in Gaia's aggregate data. This ultimately filtered Gaia's findings to 1,295,502 actual quasars, according to a paper published Monday in The Astrophysical Journal.
The resulting quasar catalog isn't the biggest by quantity, but it's "the catalog with the largest total volume of the universe mapped," according to astrophysicist and catalog co-creator David Hogg. Hogg and his colleague, postdoctoral researcher and lead study author Kate Storey-Fisher, told Phys.org the catalog is already sparking new science "from the initial density fluctuations that seeded the cosmic web…to the motion of our solar system through the universe."
Quasars are often found at the center of galaxies, which are surrounded by dark matter. This mysterious, invisible matter influences how galaxies form and evolve, affecting the supermassive black holes that power quasars. By studying the distribution of quasars across this 3D map, astronomers will hopefully gain new insight into how dark matter works—and exactly what it is.
