Artistic view of a close-up of a supermassive black hole. This image shows the material surrounding the black hole, which ultimately will fall in the central region releasing the X-ray radiation detected in this work.
Credit: NASA/CXC/A.Hobart
This composite image shows a small section of Chandra Deep Field South image, where the sources seen by Chandra are blue. Deep optical and infrared images from the Hubble Space Telescope are shown in green and blue and red and green respectively. Yellow circles are plotted to show the positions of very distant galaxies seen to exist when the Universe is less than about 950 million years old.
Credit: NASA/CXC/U.Hawaii/E.Treister et al
LONDON: Supermassive black holes littered the early universe and have been growing in tandem with their host galaxies since early cosmic time, according to new evidence.
X-ray images of deep space taken by NASA's Chandra telescope have provided the first direct observations of a hidden population of black holes, located in the infant universe less than a billion years after the Big Bang.
These findings shed significant light on the evolution of galaxies and are the first step in answering critical questions about how black holes form.
"Until now, we had no idea what the black holes in these early galaxies were doing - or if they even existed," said Ezequiel Treister from the University of Hawaii, lead author of the study published this week in Nature. "Now we know they are there, and they are growing like gangbusters."
30 million baby black holes
Until recently, astronomers relied on theoretical modelling to picture the early universe because of the difficulties in observing the furthest regions of space.
Early in 2010, the Hubble Space Telescope provided the first images of the most distant realms, showing 13 billion year old galaxies predicted to contain black holes at their centres.
Astronomers have since identified a small number of 'quasars', brilliantly luminous beacons powered by giant black holes. However they remained unable to detect most of the black hole activity in the first billion years after the Big Bang.
Babies to grow into giants
In this latest study, U.S. researchers have directly observed black holes in galaxies aged between 700 million and 950 million years old. The results indicate there may be as many as 30 million supermassive black holes in the early universe, growing significantly faster than previously thought.
"It appears we've found a whole new population of baby black holes," said co-author Kevin Schawinski from Yale University. "We think these babies will grow by a factor of about a hundred or a thousand, eventually becoming like the giant black holes we see today."
Teaming up Chandra and Hubble
The astronomers examined X-ray images of a patch of the sky known as Deep Field South taken by NASA's Chandra Observatory.
X-rays are released when gas falls into black holes and are therefore the most common way to detect these voids in space. However, the Chandra image alone proved unable to detect any sign of these emissions in the most distant realms.
So the group coupled the Chandra data with pictures from the Hubble telescope, showing the specific location of early galaxies in Deep Field South. By combining X-rays from a stack of 197 galaxies, they were able to detect a statistically significant signal - direct evidence for the presence of black holes.
