A recent study, using data from JWST, analyzed the rotation of 263 distant galaxies, surprisingly finding that about 2/3 of them rotate clockwise, while only 1/3 rotates counterclockwise.
This imbalance challenges current cosmological theories, which predict a more or less equal distribution of the rotation directions of galaxies in an isotropic universe, that is, without a preferred direction.
The study was led by Lior Shamir, associate professor of computer science at Kansas State University, as part of the JWST Advanced Deep Extragalactic Survey (JADES) program.Shamir used high-resolution images from JWST to study the galaxies' shapes and determine their rotation direction. The difference between the number of galaxies rotating clockwise and counterclockwise becomes even more pronounced when observing galaxies at greater distances, corresponding to older times in the universe.
The study suggests that this asymmetry may not be random and raises fundamental questions about the structure and origin of the universe. According to Shamir, there are two primary possible explanations for this phenomenon:
- The universe itself could have been born with an intrinsic rotation, an idea that contradicts the standard cosmological model according to which the universe is isotropic and homogeneous. If confirmed, this theory would imply that our current knowledge of the cosmos is incomplete and requires revision.
- The rotation of the Earth around the center of the Milky Way could influence observations. Light from galaxies, rotating in the opposite direction to the Earth's motion, appears brighter due to the Doppler effect, leading to an overrepresentation of these galaxies in the data. If this hypothesis is correct, measurements of cosmic distances could be incorrect and would require recalibration.
From a scientific perspective, this discovery is significant because it calls into question some of the foundations of modern cosmology. The standard model of the universe, based on the cosmological principle of homogeneity and isotropy, predicts that galaxies have randomly distributed directions of rotation. The observation of such a strong asymmetry could indicate that the universe has a "preferential direction" or that the physical processes, governing the formation of galaxies ,are more complex than previously thought. Furthermore, if the universe was born in rotation, this could link to speculative theories, such as that our universe is inside a rotating black hole, an idea proposed by some theoretical physicists.
Another important aspect is that this asymmetry increases with distance: the further back in time you look (and therefore further into space), the greater the imbalance. This suggests that the phenomenon could be linked to the initial conditions of the universe, offering a unique window to study the Big Bang and cosmic evolution.
Practically speaking, Shamir's results could have direct implications for observational astronomy. If the asymmetry is due to a bias related to the rotation of the Milky Way, as suggested by the Doppler effect, this would mean that measurements of the distances to distant galaxies – which are essential for calculating the expansion rate of the universe (the Hubble constant) – could be inaccurate. A recalibration of these measurements could resolve some known discrepancies in cosmology, such as differences in the values of the Hubble constant measured by different methods or the existence of galaxies apparently older than the universe itself according to current estimates.
In addition, the James Webb Telescope, with its ability to observe distant galaxies in unprecedented detail, remains a game-changer. This study demonstrates how its technology can not only confirm existing theories, but also raise new questions that push the limits of our understanding of the cosmos.
In essence, Shamir's study highlights a fascinating and potentially revolutionary anomaly: most of the galaxies observed by JWST appear to be rotating in the same direction, an observation that could reflect a fundamental property of the universe or an error in our measurement techniques. Scientifically, it opens the way for new research to test these hypotheses and delve deeper into the nature of the cosmos. In practice, it could lead to a revision of the methods by which we measure the universe, improving the precision of our cosmic maps.
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Image description: "Spiral galaxies imaged by JWST that rotate in the same direction relative to the Milky Way (red) and in the opposite direction relative to the Milky Way (blue). The number of galaxies rotating in the opposite direction relative to the Milky Way as observed from Earth is far higher (Shamir 2024e)".
Credit: Kansas State University
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