Space

Black Hole Treasure Trove Revealed by Deepest X-Ray Image Ever

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NASA’s Chandra X-ray Observatory has provided an international team of astronomers an unparalleled image showing the growth of black holes over billions of years starting shortly after the Big Bang. The image is the deepest X-ray ever obtained and it was collected with eleven and a half weeks (about 7 million seconds) of Chandra observing time.

The image comes from Chandra’s Deep Field – South. The highest concentration of supermassive black holes ever seen is seen in the central region of the image. The image contains about a billion objects over the entire sky and about 5,000 that would fit into the area of the Moon.

Niel Brandt, the Verne M. Willaman Professor of Astronomy and Astrophysics, and professor of physics, Penn State, led a team of astronomers studying the deep image. He explained that with this one picture, the earliest days of black holes in the Universe can be explored and the team can see how they changed over billions of years.

Approximately 70% of the objects in the new image are supermassive black holes ranging in mass from about 10 billion times to 100,000 times the mass of the Sun. Gas falling towards these black holes produce bright X-ray emission as it becomes much hotter when it approaches the point of no return or event horizon. Team member Bin Luo, professor of astronomy and space science, Nanjing University noted that as black holes in the early Universe are so far away, they can be very difficult to detect because they only produce radiation if they’re pulling in matter actively.

The full image field covers an approximately circular region on the sky with an area about two-thirds that of the full moon. However, the outer sectors of the image, where the sensitivity to X-ray emission is lower, are not shown here. The colors represent different levels of X-ray energy detected by Chandra. Here the lowest-energy X-rays are red, the medium band is green, and the highest-energy X-rays are blue. The central region of this image contains the highest concentration of supermassive black holes ever seen, equivalent to about 5,000 objects that would fit into the area of the full moon and about a billion over the entire sky. (Image Credit: X-ray: NASA/CXC/Penn State/B. Luo et al)
The full image field covers an approximately circular region on the sky with an area about two-thirds that of the full moon. However, the outer sectors of the image, where the sensitivity to X-ray emission is lower, are not shown here. The colors represent different levels of X-ray energy detected by Chandra. Here the lowest-energy X-rays are red, the medium band is green, and the highest-energy X-rays are blue. The central region of this image contains the highest concentration of supermassive black holes ever seen, equivalent to about 5,000 objects that would fit into the area of the full moon and about a billion over the entire sky. (Image Credit: X-ray: NASA/CXC/Penn State/B. Luo et al)

If Chandra is however used to stare long enough, astronomers can find and study large numbers of growing black holes, some of which appeared shortly after the Big Bang. Astronomers can explore ideas about how supermassive black holes grew about one to two billion years after the Big Bang by using the new ultra-deep X-ray image. The researchers have already shown that these black holes in the early Universe don’t grow via the slow accumulation of matter, but mostly in bursts.

The team also have found hints that the seeds for supermassive black holes may not be light with about 100 times the Sun’s mass, but rather heavy with masses about 10,000 to 100,000 times that of the Sun. This addresses important speculations in astrophysics about how these objects can grow so fast to reach masses of about a billion times the Sun in the early Universe.

X-rays from massive galaxies at distances of up to about 12.5 billion light years from Earth have also have detected. Most of the X-ray emission from the farthest galaxies probably comes from large collections of stellar mass black holes inside the galaxies. These black holes typically weigh a few to a few dozen times the mass of the Sun and were formed from the collapse of massive stars.

Team member Fabio Vito, postdoctoral scholar in astronomy and astrophysics, Penn State observed that they are able to learn more about the evolution and formation of supermassive black holes and stellar mass in the early Universe by detecting X-rays from distant galaxies. By doing so, they are looking back at times when black holes were in critical phases of growth.

The team combined very deep Hubble Space Telescope data with the Chandra X-ray data over the same area of sky to perform this study. They looked at X-ray emission from over 2,000 galaxies that were identified by Hubble, and are located between about 12 and 13 billion light years from Earth.

To provide a certain solution to the secret of how supermassive black holes can quickly reach large masses, more work using Chandra and other X-ray observatories will be required. The James Webb Space Telescope will provide observations of a larger sample of distant galaxies. This will extend the study of X-ray emission from black holes to even greater distances from Earth.

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