Exposing Black Holes Disguised in Dust
This zoomed-in view of a portion of the all-sky survey from NASA's Wide-field Infrared Survey Explorer shows a collection of quasar candidates. Quasars are supermassive black holes feeding off gas and dust. The larger yellow circles show WISE quasar candidates; the smaller blue-green circles show quasars found in the previous visible-light Sloan Digital Sky Survey. WISE finds three times as many quasar candidates with a comparable brightness. Thanks to WISE's infrared vision, it picks up previously known bright quasars as well as large numbers of hidden, dusty quasars.
The circular inset images, obtained with NASA's Hubble Space Telescope, show how the new WISE quasars differ from the quasars identified in visible light. Quasars selected in visible light look like stars, as shown in the lower right inset; the cross is a diffraction pattern caused by the bright point source of light. Quasars found by WISE often have more complex appearances, as seen in the Hubble inset near the center. This is because the quasars found by WISE are often obscured or hidden by dust, which blocks their visible light and allows the fainter host galaxy surrounding the black hole to be seen.
Image credit: NASA/JPL-Caltech/UCLA/STScI