Using a technique known as gravitational lensing and NASA's Chandra X-ray Observatory telescope, astronomers have caught a glimpse of a duo of supermassive black holes that existed when the Universe was just 2 billion years old.
The process is allowing astronomers to check out distant and faint X-ray objects like these black holes in unprecedented detail, as well as stare back in time to a period when the Universe was just a fraction of its current age of around 14 billion years old. X-ray objects are cosmic bodies that emit strongly in the X-ray region of the electromagnetic spectrum. These include, stars, supernovae, and the regions around black holes.
The X-ray emitting objects in question are 12 billion light-years away from Earth and are likely to be double growing supermassive black holes that are separated by just 650 light-years, according to a study set to be published in The Astrophysical Journal.
While Chandra has made observations of growing supermassive black holes in both pairs and trios before, these are usually much closer to the Earth, or they are separated from each other by much greater distances. This is the first time the observatory has been able to distinguish such a pairing at such a distance and at such close proximity to each other.
The objects exist as part of the MG B2016+112 system and were initially found in radio-wave emissions from the system. The radio data indicated the presence of two supermassive black holes, each of which seemed to be emitting a jet of material.
This highlighted the area for follow-up study by Dan Schwartz of the Center for Astrophysics, Harvard & Smithsonian (CfA), and his team. If the region was to be examined in greater detail and the suspected black holes distinguished, however, this would require using X-ray emissions.
"The overwhelming majority of extragalactic point sources [those outside the Milkyway] that are seen in X-rays, are from supermassive black holes. Especially in the early universe. X-rays are especially useful to distinguish black holes from galaxies," Schwartz told Newsweek. "Black holes and galaxies are involved in the growth of each other, so it is important to trace this history over cosmic time."
Because the X-ray emissions from MG B2016+112 system are so faint the only way to do this effectively was to employ the phenomenon of gravitational lensing and a natural X-ray lens—an object of tremendous mass—which can enhance the signal of light.
Gravitational lensing is a phenomenon predicted by Albert Einstein in his theory of general relativity. This suggests that objects of great mass like galaxies, black holes, and stars "warp" space. This causes light to curve as it passes the objects, and as a result, the emission is often amplified or enhanced.
That means that when a galaxy exists between us and the source of a light emission it can act almost like a cosmic magnifying glass—greatly enhancing the view of objects behind it.
With the use of such an intervening galaxy as a lens, Schwartz and his team were able to distinguish three separate X-ray sources from two supermassive black holes with a small separation.
The light from one black hole was warped to produce two beams, while the light from the fainter object formed a single source. The finding is a real proof of concept for the use of gravitational lensing to enhance X-ray source detection, as the X-ray emission from the fainter of the two sources was amplified by around 300 times, meaning that it wouldn't have been visible with another technique.
"Without lensing, this observation would have required 600 hours of observing, and would have revealed only a single point source of X-rays," Schwartz said. "That point source could be located to be only within about 12,000 light-years of the radio source. With lensing, we located the source to be within about 250 light-years of the radio source."
In addition, the research could help astronomers discover how supermassive black holes grew to such tremendous sizes in the early Universe.
This article has been updated with comment from Dan Schwartz.
