While we still barely know anything about supermassive black holes at this point in time, scientists do have theories on how they formed. One suggests that they're the result of several smaller black holes merging into one. Another theory says these supermassives gobble up more food (that is, gas and dirt) from their surroundings. However, scientists believe that some of the biggest black holes took form merely a billion years after the Big Bang, and both those processes would've been too slow to reach the mass they have. According to Andrea Ferrara, one of the study's authors, their work suggests that supermassives "start big and grow at the normal rate, rather than starting small and growing at a very fast rate."

The astronomers in this study pulled out and combined data from Hubble, Chandra X-ray Observatory and Spitzer Space Telescope to find potential supermassive black hole seeds. They found two strong contenders, but we'll have to wait for quite some time for a follow up. They still need to gather more data, most likely from upcoming observatories such as the James Webb Space Telescope, for confirmation.