We've known for some time that there are a large number of black holes out there in the universe, but it turns out previous estimates undershot the actual numbers by quite some margin. Thanks to the results of a broad scan of the sky by NASA's Wide-field Infrared Survey (WISE) telescope, we now know the number of black holes is actually much, much greater than we thought.
The WISE telescope, which uses infrared technology to locate light sources that other telescopes can't see, spent more than a year scanning the entire sky before wrapping up its mission in February 2011. The "all-sky" survey generated so much data that NASA astronomers are still poring through it all, and this week they finally released the results of WISE's efforts to locate black holes. So how many did it find?
That might not seem like much when compared to estimates of how many stars exist, but considering it's more than three times the number astronomers previously spotted, it's a big find, so big that NASA astronomer Daniel Stern labeled it a "bonanza."
And these aren't just little pockets of swirling darkness out in the middle of the sky. No, these black holes are described as "supermassive" cosmic entities known as quasars that devour nearby matter and release light as a byproduct. It's this light from the quasars, some of the brightest objects in the universe despite what you think of when you hear the term "black hole," that WISE was able to detect.
"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."
But the quasars aren't the only space goodies NASA's found in the WISE data. They've also picked up on about 1,000 rare galaxies dubbed "hot DOGs," for "hot, dust-obscured galaxies." Astronomers believe these galaxies would appear much brighter, but they are obscured by dust (hence the name). Based on their location, it's also believed that they existed in the earliest days of the universe because of how long (billions of years, most likely) it took for their light to make it to Earth. Though hot DOGs could be a new type of galaxy, astronomers think it's more likely that they represent a transitional phase between spiral and elliptical galaxies, and they even suspect that our Milky Way galaxy could become a hot DOG when it collides with the Andromeda galaxy in about 2 billion years.
"We think we may be seeing these galaxies at a crucial transformational stage," said Rachel Somerville, an astrophysicist at Rutgers University.
So, we've got many, many more black holes than we've ever previously seen, and a bundle of extremely rare galaxies that may explain galactic evolution much better. But here's the coolest thing: NASA's not done looking through all the WISE data yet, so who knows what else they might find?