ESO/M. Kornmesser

If you want to cook up a stellar-mass black hole, it’s fairly easy. Take a massive star, wait until it has consumed all its elemental fuel, watch the blinding supernova, and before you know it, you have a black hole. Now, if you want to create a supermassive black hole — one that’s a million to a billion times the mass of the Sun — the process becomes more complicated.



Astronomers have found evidence of many supermassive black holes in the most distant reaches of space, corresponding to when our universe was very young — just 5 percent of its present age. While it’s possible for an average-sized black hole to grow to supermassive proportions, it generally takes a long time — more time than was available by that point.



These observations thus pose a conundrum: How could these supermassive black holes have formed so quickly in the early universe?



A collaboration of Japanese and German researchers believes they have solved the puzzle. Using computer simulations, the researchers recreated conditions found in the early universe to see if they could create a supermassive black hole. Unlike previous models, their simulations factored in supersonic gas streams left over after the Big Bang. That change allowed supermassive black holes to form in a short period of time, in numbers that closely match the population of supermassive black holes we see.



"This is significant progress. The origin of the monstrous black holes has been a long-standing mystery and now we have a solution to it," said author Naoki Yoshida of the Kavli Institute for the Physics and Mathematics of the Universe in a statement.



In the simulations, the researchers looked in dark matter halos — the clumps of dark matter where galaxies form. As they watched, the motion of the gas streams and their interaction with the dark matter initially stifled formation of early stars. By the time the gas finally collapsed into a star, the dark matter halo had coalesced so much mass that the star was able to grow to elephantine proportions, eventually reaching 34,000 times the mass of the Sun. Then, unable to support its own weight, the star collapsed, forming a supermassive black hole.