Exotic objects made of dark energy could be pushing the universe apart
Simulated images showing the expansion of the universe (left to right), with the locations for where GEODEs would form (green dots) before they migrate into the darker, emptier areas
University of Hawaii
The universe is expanding, and that expansion is accelerating, but exactly why and how that’s happening remains unknown. One hypothesis suggests that this expansion is driven by mysterious, black hole-like objects made of dark energy, and now astrophysicists have theorized how these objects work their magic on the cosmos – and where they all went.
We』ve known for the better part of a century that the universe isn’t static – it’s expanding. But the story became even stranger in 1998 when two teams of astrophysicists independently came to the surprising, Nobel-Prize-winning conclusion that the speed of this expansion is accelerating.
The driving force behind this acceleration has been given the descriptor 「dark energy,」 and it’s been calculated that this stuff makes up around 68 percent of everything in the universe. But we still don’t really know what it actually is.
One fringe hypothesis suggests that this unknown form of energy could be lurking inside an exotic class of objects referred to as Generic Objects of Dark Energy (GEODEs). These objects would look very much like black holes to outside observers, but they would be made up of a core of dark energy, surrounded by a spinning layer.
And now, a new study has suggested an explanation for how these GEODEs might be accelerating the expansion of the universe – and where we might find them.
Researchers from the University of Hawaii calculated that the speed at which the outer layers spin changes how they move relative to each other. If they spin slowly, the GEODEs would clump together very quickly – more quickly than black holes do, in fact. That’s because of the mind-bending detail that GEODEs would gain mass from the expansion of the universe itself.
But if the outer layers are spinning much faster, near the speed of light, then the GEODEs begin to repel each other. And this repelling effect, the team says, could be what largely drives the acceleration of the expansion of the universe.
「The dependence on spin was really quite unexpected,」 says Duncan Farrah, co-author of the study. 「If confirmed by observation, it would be an entirely new class of phenomenon.」
The researchers say that the new study supports the idea that, if they exist, GEODEs could rather neatly solve the dark energy problem. By making adjustments to some of Einstein’s equations, the team calculated how that might work.
In the scenario they describe, many of the first stars ever born could have formed GEODEs instead of black holes at the end of their lives. Over time, those GEODEs would have sucked up stars, dust, gas and other material, slowly growing bigger and spinning faster. As they sped up, they would instead begin to repel each other, as well as basically everything else in the universe – contributing to the accelerated expansion.
The team says that this story is consistent with other observations of the cosmos. There were enough ancient stars to produce the amount of GEODEs that would explain the acceleration measured, and GEODEs wouldn’t have messed with the cosmic microwave background because they were born hundreds of millions of years after this radiation was emitted.
And most importantly, they wouldn’t have disrupted the formation of galaxies because they would have pushed themselves away from luminous matter before the galaxies were even a twinkle. In fact, that’s where these objects may still be lurking today – in the big empty voids between galaxies.
Of course, fitting these objects into an existing story is one thing – trying to find direct evidence is another entirely. And the team says that proving GEODEs exist would be difficult, since they would look very much like black holes, even when measured using gravitational wave observatories. But further investigation could help uncover new leads.
The research was published in the Astrophysical Journal.
https://iopscience.iop.org/article/10.3847/1538-4357/abad2f
Source: University of Hawaii
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