Dark Matter Could Solve the Mystery of Supermassive Black Hole Formation
New cosmological research from the University of California Riverside connects two of the universe’s most perplexing phenomena: supermassive black holes and dark matter. According to physicist and astronomer Hai-Bo Yu, dark matter could be the key to understanding how enormous black holes formed in the early universe. This work is all based on simulations, but we might have the means to verify Yu’s work experimentally before long.
Supermassive black holes can have millions or billions of times more mass than the Sun. It is believed that most large galaxies have a supermassive black hole in their centers. The one in the Milky Way is called Sagittarius A* (pronounced “Sagittarius A Star”). Scientists famously imaged the supermassive black hole at the center of galaxy M87 in 2019 (see above).
As scientists peer deeper in the universe, they also look further back in time. One surprising feature of the universe during its younger eons is the presence of supermassive black holes. The origin of these enormous collapsed stars is still murky, and one of the most perplexing aspects is how they existed in the early universe at all. The initial “seed” black hole would need to be much larger than the average black hole these days. Alternatively, those early singularities could have grown much faster than they do today.
Dark matter is a mystery of its own because it does not interact with normal matter in any way except for gravitation. We can observe the effects of dark matter on normal matter, even if we can’t see it. For example, the halo of dark matter that surrounds most, if not all, galaxies in the modern universe. The simulation created by Yu’s team starts with a similar halo of dark matter with one important distinction: Although the simulated halo cannot interact with normal matter, it can interact with other dark matter.
Under these conditions, the study claims that dark matter that can interact with itself would transfer energy between particles, causing friction and reducing angular momentum. Eventually, these forces cause the cloud to collapse and form a large seed black hole. According to Yu, this property would explain what we see in very old black hole populations. To know for sure, we’d need to observe dimmer celestial objects from the first few billion years of the universe. That’s beyond our current capabilities. Luckily, upcoming instruments like the James Webb Space Telescope should be able to do just that. NASA is currently hoping to get the Webb telescope into space by the end of the year.
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