The story of the early universe is one that astronomers are filling in with each new observation. To look back across billions of years of time, across the light-years, takes some pretty complex instruments and long observations. The story, as we know it from those studies is really intriguing.
First, we have the origin of the universe, which we actually cannot directly detect. That occurred nearly 14 billion years ago, and fairly soon after this “Big Bang” happened, there was a period of darkness called “The Dark Ages”. That was a time that the newly born universe was cooling. Eventually, conditions allowed light to pass through the masses of hydrogen and helium that existed at the time.
The period after the Dark Ages is the Epoch of Reionization, and it’s when the first stars could shine out. At that point, the first galaxies were starting to form. They were cuddled into various shapes by the gravitational influence of dark matter.
That’s sort of the executive summary of the first epochs of the universe. It would look strange to our eyes: first, just masses of gas, and, of course, darkness. Then, the formation of hugely massive monster stars, and clumps of material that would later become galaxies. It was a baby universe busily evolving and growing up using what it had at hand. There were black holes, too. But, no planets and no life.
Shaping Galaxies
Galaxy formation and evolution is another area where astronomers are still busy telling a story. The general tale is that galaxies form by cannibalizing and merging with each other. It started with little shreds of galaxies that existed more than 13 billion years ago. They collided, accreted, and got bigger. Galactic mergers and acquisitions still happen. And, somehow, black holes are involved. That part of the story is still very much under development.
Astronomers used the Very Large Telescope in Chile to look at a very curious grouping of galaxies around a black hole. This image shows an artist’s concept of what it might look like if you could be close by. There are six galaxies, all arrayed around a supermassive black hole in a cosmic “spider web” that is about three hundred times the size of the Milky Way Galaxy. The whole assemblage lies about 13.1 billion light-years away, in the direction of the constellation Sextans.
The fact that they saw such a supermassive black hole so early in the universe is a tantalizing clue to the development of these odd monsters of the cosmos. To get black holes, you need massive stars. In the early universe, the first ones would have died fairly quickly and formed black holes. To get a supermassive one takes a lot of stellar-mass black holes and then, somehow, they need to get crammed together to make a black hole of a billion solar mases. That takes time, too.
So, one of the big questions is “how do you get enough fuel to make these supermassive black holes so early and so fast in the history of the universe?”
Early Universe Mix: Galaxies, a Black Hole and Dark Matter
The answer could be right in front of us now. The six galaxies arrayed around the black hole are likely providing the fuel to turn a massive black hole into a supermassive one. There’s also another key ingredient needed: dark matter. It’s likely shaping the whole collective with its gravitational influence.
The observations of this six-galaxy collection and its black hole are another important clue to conditions in the early universe. They show that giant haloes of this unknown “stuff” are also part of creating the web-like structure around the six galaxies and their companion black hole. Understanding that, and finding more examples of such activity in the infant cosmos help explain more details of conditions “way back when”. Stay tuned!