Scientists Have Spotted Unprecedented Black Holes in the Early Universe

Scientists have spotted a pair of supermassive black holes located at the center of merging galaxies that existed more than 10 billion years ago, during an era known as “cosmic noon,” providing the earliest glimpse of such a close interaction between galactic giants, reports a new study.

The discovery of the gargantuan black holes, which are each about 300 billion times as massive as the Sun, opens a new window into the evolution of these cosmic behemoths that occupy the cores of large galaxies, including the Milky Way. Scientists think that black holes in the early universe grew to their enormous scales through a series of mergers between smaller black holes, but the new observations are the first to reveal these objects in such tight proximity—just a few thousand light years apart—during this influential era when the universe was between two and three billion years old.  

A black hole is an ultra-compact object endowed with such immense gravity that nothing—not even light—can escape its border, which is known as an event horizon. Whereas small black holes can be instantly forged from the brief explosions of large stars, the supermassive black holes (SMBHs) found at the center of galaxies are typically many millions of years in the making. Some of these SMBHs can power quasars, which are ultraluminous objects fueled by interactions between the black holes and material in the disks surrounding them.

Exactly how SMBHs evolved is a major question in astronomy that could shed light on the configuration of the modern universe. Cosmic noon is an ideal time to look for these clues, because this era was defined by intense galactic growth spurts and supercharged star formation. But SMBHs that interact on kiloparsec scales—where one kiloparsec equals 3,261 light years—have never been seen during cosmic noon because it is difficult to spot finer details of these pairs so far back in time.

Now, scientists led by Yu Ching Chen, a graduate student studying astrophysics at the University of Illinois at Urbana-Champaign, have finally snagged this long-sought glimpse of a kiloparsec-scale pair of supermassive black holes powering quasars at cosmic noon. 

The team used several sophisticated telescopes to identify an object known as SDSS J0749 + 2255 as a “dual-quasar system” that “fills a long-standing gap in the expected population of dual quasars” in the early universe, according to a study published on Wednesday in Nature. 

“We are very excited to report this new discovery,” Chen said in an email to Motherboard. “It’s not a trivial job to put together evidence from various telescopes. The whole process of proposing, obtaining data, and analyzing data, takes a large amount of time.” 

“Luckily, we have experts from various institutes that helped us analyze this huge amount of data,” he continued. “We are glad that we finally put the puzzles together and show a case study of our project. We look forward to investigating a large sample and building a statistical study.”

For years, scientists have hoped to spot one of these systems at cosmic noon because these pairs are in the final stages of coalescing into a single SMBH. As a result, dual-quasars in this ancient age offer a glimpse of the early evolution of SMBHs, and the galaxies that host them. However, it’s challenging to distinguish whether a distant observation is actually a dual-quasar system, or if it is simply one quasar that looks like a pair due to a trippy optical illusion known as gravitational lensing.

“The observed structure of the universe suggests that galaxy mergers and the co-evolution of their central supermassive black holes (SMBHs) are common throughout the cosmos,” Chen explained. “The cosmological simulations also show that SMBHs become active (e.g., quasar) during galaxy mergers.”

“However, systematic searches of dual quasars at galactic scales (~kilo-parsecs) at cosmic noon…are limited by the stringent angular resolution requirement,” he continued. “The discovery of J0749+2255 suggests that those systems do exist and can help us to understand how SMBHs accrete and interact with their host galaxies.”

Chen and his colleagues were able to make this breakthrough by carefully observing  J0749+2255 with some of the most precise observatories in operation. The team first imaged the system with the European Space Agency’s Gaia satellite, a mission that is able to resolve the positions and movements of outer space objects with unprecedented accuracy. Then, the researchers used the Hubble Space Telescope to zoom in on the system in order to confirm that it really did contain two quasars, rather than a double-image of the same quasar.

The success of the technique raises the possibility that more of these systems could be identified at cosmic noon, which would yield further insights into the origin of SMBHs that abound in the modern universe. Chen noted that future observations of dual-quasars in the early universe could help to constrain cosmological simulations, while also revealing the epic co-evolution of black holes and their host galaxies.

“Finding one system is definitely exciting, but a more statistical study with a large sample is necessary to answer many questions in astronomy,” he concluded.