Imagine it could well turn out that there’s a gigantic black hole, lying in wait in the cosmic dawn, a few hundred million years after the Big Bang, weighing in at over a billion times the mass of our Sun. Sounds far-fetched, right? Well, it’s very real, and astronomers are scratching their heads.
One such giant dweller rests at the heart of a galaxy known as J1120+0641. This black hole, over a decade ago, was discovered to be of interest to experts due to its gargantuan size and surprising “normalcy.” Using the James Webb Space Telescope, a team of researchers led by astronomer Sarah Bosman of the Max Planck Institute for Astronomy managed to get a closer look, and what they turned up didn’t make things any easier to explain.
Now, black holes get fat by consuming gas and dust, sometimes even stars. Evidence of feeding should be left behind during the process; this would include super-bright emission generated by enormous friction and gravity. In contrast, nothing in J1120+0641 shows extreme feeding behavior. It has just been eaten very normally, which allows it to be all the more baffling in terms of its enormous mass.
If these were not such gourmand black holes, effective at chomping up their surroundings, how did they become so large, so quickly? One theory is that they began from “large seeds”—enormous clumps of matter or huge stars up to hundreds of thousands of times the mass of our Sun. This would head start them by a very large amount.
Not to mention, the J1120+0641 is not a unique weird case. Another recent discovery, a black hole residing at the center of the galaxy COS-87259, was cloaked in stardust—growing up really fast at a not very extraordinary rate. This black hole is also from the early universe and makes our understanding even more complicated.
This necessarily made the explanation of the existence of very early luminous quasars a big challenge in extragalactic astronomy, given how briefly there is time to grow such a huge black hole since the Big Bang, says Ryan Endsley, an astronomer at the University of Texas, Austin.
The results suggest that probably thousands more such massive black holes lurk in the early cosmos than previously thought. If so, this could point to a gap in our understanding of forming galaxies and black holes in the early universe.
Drawing from the improved latest findings, a successful advanced space telescope, JWST, which began its mission in 2022, has been seminal in spotting these ancient cosmic giants. Looking deep into space, we are able to gaze further back in time to the great universe at only a fraction of its present age. This kind of technology is hence crucial in unraveling mysteries behind black holes and their rapid growth in the early universe.
One might think, perhaps, that black holes in the young universe simply grew rapidly by plunging into some kind of “super-Eddington accretion” phase, in which they gulped matter faster than their radiation could push it away. However, the JWST observations gave no hint of supporting this view. Indeed, the light from J1120+0641 looked similar to that from more “modern” quasars, finding that questions whether these early black holes had some kind of feeding advantage.
That dust around these early black holes is a bit hotter than that which we see around quasars that are closer and more recent, a tiny difference that might give clues about conditions in the still-young universe but alone isn’t enough to explain how they grew up so fast.
This also means that this early black hole population has a tie-in with the JWST discovery of six enormous galaxies that were spotted aged between 500-700 million years after the Big Bang, so massive that they rule out 99% of the existing cosmological models in their entirety. One review paper stated that we may be viewing only the “tip of the iceberg” in early black holes, suggesting that many others could be out of sight.
Mysteries surrounding black holes in the early universe are far from resolved. Whether these were massive seeds or some other unknown process, these findings have been forcing astronomers to update their models and theories. The more discoveries that come to light, the closer we’ll be to answering what enigmatic giants have been lurking since the beginning of time.
Hence, the next time you happen to cast your gaze up out toward the night sky, remember that somewhere out there, further back in time. One coastline of black holes is massive, mysterious, inexplicable as things stand. Every further discovery brings us a little closer toward unlocking those secrets of the universe.
