How supermassive black holes spawned so fast billions of years ago

Contributed by
Nov 21, 2017

Somewhere in the chasm of interstellar space are supermassive black holes so ancient, they came into being just as the universe was born, and there are secrets they could tell us that have been in the dark for that long.

To give you an idea of exactly how long these enormous collapsed stars are, astronomers found that they were around since our universe was an almost unfathomable 5 percent of its current age. They also formed so fast that they would have never gotten to the size they are now if they had grown at the average rate. If you’re wondering what the average rate is, let’s just say normal black holes (if you can call a black hole “normal”) don’t reach supermassive status too easily. It literally takes ages for them to grow that monstrous.

Supermassive black hole formation theories have suggested everything from UV light interference—which prevented gas clouds from turning into stars until the clouds collapsed into immense black holes—to the merging of several black holes into one of these behemoths, but either of these would involve phenomena that is unlikely to have occurred at the dawn of the universe. Now a research team that recently published its findings in the journal Science has finally shed light on this mystery using computer simulations. Japanese and German scientists digitally recreated conditions from billions and billions of years ago to see how long it would have taken for a supermassive black hole to form in the early universe. They factored in one thing previous simulations have left out: supersonic gas streams left in the wake of the Big Bang.

The supermassive black hole that lurks in the heart of galaxy NGC 5548. Credit: ESA

Leveling up the simulation revealed supermassive black holes emerging within a much shorter period of time than would have been expected without the boost. The scientists recreated a nascent universe in which galaxies were shrouded by dark matter haloes. Inside these haloes, the way those gas streams moved and interacted with the dark matter caused a delay in the time it took for the gas to collapse into a star. By then it was already too late.

Wait too long for a star to get it together, and when that star-gas finally does collapse into what should be another glowing orb in the sky, so much mass will have accumulated in the dark matter halo that the embryonic star will grow out of control. Think around 34,000 times the mass of our sun. Fireballs that colossal can’t support their own weight for long, which explains their rapid collapse into supermassive black holes.

Mind-blowing results like these still can’t tell us everything the relics of the early universe are hiding from us. It could be that supermassive black holes in various galaxies formed under completely different circumstances, and that either those improbable theories could turn out to be viable or that there is still some other undiscovered formation process out there.

When NASA launches its James Webb Space Telescope in 2019 and ESA's mission to observe the X-ray emissions from these galactic monsters takes off in another decade, the observations beamed back to Earth could illuminate things that even astronomers never could have imagined.