When you peer out into the depths of the cosmos, a mystery lies there, waiting.
In a survey of the deep sky, most of the galaxies are seen rotating in the same direction. This is a problem. Under current models of the way the Universe behaves, galaxies should be a hodge-podge rotating whichever dang way they please, resulting in a roughly even distribution of rotations.
The fact that this is not what we observe suggests that there’s something hinky going on: a huge gap in our understanding of the way the Universe works.
“It is still not clear what causes this to happen, but there are two primary possible explanations,” says astronomer Lior Shamir of Kansas State University.
“One explanation is that the Universe was born rotating. That explanation agrees with theories such as black hole cosmology, which postulates that the entire Universe is the interior of a black hole. But if the Universe was indeed born rotating it means that the existing theories about the cosmos are incomplete.”
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The other, much less exciting possibility is that it’s an illusion caused by the rotation of our home galaxy.
Although the Universe might appear pretty random at a glance, there is actually quite a bit of structure therein. Vast filaments of dark matter span the cosmos in a gravitational web that connects galactic hubs, for example. We had assumed, however, that the behavior of galaxies within that web was pretty randomized.
That means that the distribution of spin directions of these galaxies should be more-or-less equal. Shamir’s body of research suggests otherwise; previously, he has found evidence that the distribution of galaxy spin directions across the sky forms a distinct pattern.
In the course of his research, Shamir has noticed that there’s an asymmetry in the spin distribution; and, at greater distances across space-time, the asymmetry becomes even more pronounced. That means that there are more galaxies spinning one way than galaxies spinning the other, and the difference is stronger earlier in the Universe.
For this new paper, he used data collected during the JWST Advanced Deep Extragalactic Survey (JADES) to study the rotations of 263 galaxies, whose light has traveled between roughly 5 and 10 billion years to reach us.
There are only two directions these galaxies can spin – clockwise and counterclockwise. If the Universe is isotropic, or uniform in all directions, as described by the cosmological principle, there should be a pretty even 50-50 distribution of clockwise and counterclockwise galaxies throughout.
When Shamir measured the spins of the 263 galaxies in his sample, he found an asymmetry that simply cannot be explained by chance: of the galaxies 105 rotate counterclockwise, while 158 rotate clockwise.
“The analysis of the galaxies was done by quantitative analysis of their shapes, but the difference is so obvious that any person looking at the image can see it,” Shamir says. “There is no need for special skills or knowledge to see that the numbers are different. With the power of the James Webb Space Telescope, anyone can see it.”
The notion that we all live in a black hole is pretty wild, and difficult to swallow, but there may be other explanations for the asymmetry. One possibility is that the rotation of the Milky Way galaxy from which we observe has more of an effect on our observations than we thought, making some galaxies appear as though they are rotating differently.
That would be an oversight, but one to which the solution might clear up several other problems, such as the speed at which the Universe is growing.
“If that is indeed the case, we will need to re-calibrate our distance measurements for the deep Universe,” Shamir says.
“The re-calibration of distance measurements can also explain several other unsolved questions in cosmology such as the differences in the expansion rates of the Universe and the large galaxies that according to the existing distance measurements are expected to be older than the Universe itself.”
His findings have been published in the Monthly Notices of the Royal Astronomical Society.
