A Tour of PSO167-13

Narrator (April Jubett, CXC): Astronomers have discovered evidence for the farthest "cloaked" black hole found to date, using NASA's Chandra X-Ray Observatory. At only about 6% of the current age of the universe, this is the first indication of a black hole hidden by gas at such an early time in the history of the cosmos.

Supermassive black holes, which are millions to billions of times more massive than our Sun, typically grow by pulling in material from a disk of surrounding matter. Rapid growth generates large amounts of radiation in a very small region around the black hole. Scientists call this extremely bright, compact source a "quasar."

According to current theories, a dense cloud of gas feeds material into the disk surrounding a supermassive black hole during its period of early growth, which "cloaks" or hides much of the quasar's bright light from our view. As the black hole consumes material and becomes more massive, the gas in the cloud is depleted, until the black hole and its bright disk are uncovered.

The new finding came from observations of a quasar called PSO167-13, which was first discovered by PanSTARRS, an optical-light telescope in Hawaii. Optical observations from these and other surveys have detected about 180 quasars already shining brightly when the universe was less than a billion years old, or about 8 percent of its present age. These surveys were only considered effective at finding unobscured black holes, because the radiation they detect is suppressed by even thin clouds of gas and dust. Since PSO167-13 was part of those observations, this quasar was expected to be unobscured, too.

A team of researchers, however, used Chandra to find something different. They observed PSO167-13 and nine other quasars with Chandra that had been discovered with optical surveys. After 16 hours of observation, only three X-ray light particles were detected from PSO167-13, all with relatively high energies. Since low-energy X-rays are more easily absorbed than higher energy ones, the likely explanation is that the quasar is highly obscured by gas, allowing only high-energy X-rays to be detected.

This means that PSO167-13 quasar may be the most distant cloaked supermassive black hole yet seen, at 850 million years after the Big Bang. The previous record holder has been observed 1.3 billion years after the Big Bang. The researchers plan to follow up with more observations to learn more about PSO167-13 and also try to use Chandra to find other systems like it.