We may have just found the source of dark energy. No, seriously.
A set of two new papers led by researchers at the University of Hawaii at Mnoa propose that dark energy is produced by a combination of black holes and the expansion of the universe.
Black holes are fairly mysterious objects, despite how long weve been studying them. Theyre hard to observe, and they evolve over long periods of time.
Most of the time, when modeling how black holes gain mass, astronomers make a few assumptions about their behavior. These work fine on recently formed black holes, but when models built on the assumptions are applied to black holes formed by truly ancient stars, they are a lot less consistent.
So, a few years ago, the team proposed a concept that could make things line up a bit better: cosmological coupling. This is the idea that not only is the mass of the black hole influenced by the stars it eats and any other black holes it merges withits influenced by the expansion of the universe itself.
Thats not quite as wild as it seems. If a black hole expands along with the universe, that expansion generates energy. And because energy and mass are linked through everyones favorite physics equation, e=mc, if the energy increases, the mass increases with it.
With the idea of cosmological coupling in place, the question became how to prove it. The team needed to demonstrate that the expansion of the universe was strongly tied to the growth of black holes. They called the strength of this bond k.
To test the connection, the team observed five ancient populations of spiral galaxieslarge galaxies that are billions of years old and have finished mergingto see if they were gaining significant mass. In those galaxies, the central black holes arent accumulating much mass through collisions with other black holes or through swallowing huge amounts of stars.
So, the only way they could be gaining large amounts of mass would be through a connection to the expansion of the universe. And boy, were they gaining mass. The team calculated that these black holes that formed billions of years ago are anywhere from seven to 20 times more massive than similar, recently formed black holes.
That huge difference in mass lead researchers to calculate that the strength of the connection between expansion and mass increase in black holes was about k=3, a solution that feels a bit esoteric and inaccessible until its put into context.
So, heres the context: Back in 2019, it was calculated that a connection strength of k=3 meant that instead of a singularity, black holes contained whats called vacuum energya type of dark energy.
If thats true, these new observations show that all black holes are producing a constant amount of dark energy equal to our existing measurements of dark energy. All of the dark energy in the universe would be accounted for by the vacuum energy created by black holes.
This is the first time that observational data has been able to explain the entire existence of dark energy with no new sources. Everything in this study was already folded into Einsteins theories.
It still needs to be confirmed, and researchers are careful to say that this is just a first step in fully understanding the source of dark energy. The whole field of study is still very mysterious.
But in a mystery that large and unknown, a first step is a good one.
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"History shows again and again that nature points out the folly of man. Go go Godzilla!" Godzilla - Blue Oyster Cult