These black holes aren't the average tiny, dense objects created by the collapse of dead stars, but rather humongous "supermassive" black holes that have been caught feasting on matter falling into them. Such active black holes are known as quasars, and are some of the brightest objects in the universe, because of light released by the infalling matter. [Photos: Millions of Black Holes Seen by WISE Telescope]
"We expected that there should be this large population of hidden quasars in the universe, but WISE can now identify them across the sky," Stern said. "We think these quasars are really important for shaping how galaxies look today."
In addition to this haul of gorging black holes, WISE has turned up a smaller population of rarer objects researchers are dubbing "hot DOGs," for hot, dust-obscured galaxies.
These galaxies are thought to be extremely bright, but appear very faint to us because their light is shrouded by dust.
"It is actually the most obscured objects in the WISE sky that are among the brightest objects in the universe," said Peter Eisenhardt, a WISE project scientist at JPL. "They're definitely a different type of beast than we’ve seen before."
The hot DOGs observed by WISE number about 1,000, and are mostly spotted from very far away, meaning they existed in the early days of the universe, because their light has taken billions of years to travel to Earth.