Recent studies conducted by astronomers analyzing cosmic microwave background radiation indicate the presence of cosmic birefringence, a phenomenon that causes a slight rotation in the polarization of primordial light emitted approximately 380 years after the Big Bang, raising questions about the limits of current physics models.
Astronomers analyzing cosmic microwave background radiation have found new evidence of cosmic birefringence, a phenomenon that could challenge current physics models. The detected rotation in the polarization of primordial light reaches 0,215 degrees, according to recent data.
Astronomers and physicists investigate signals in the cosmic microwave background radiation.
Astronomers studying the cosmic microwave background radiation, known by the acronym CMB, have identified further evidence of a phenomenon called cosmic birefringence. The discovery raises questions about current physics models that describe the evolution of the universe.
Cosmic microwave background radiation is considered the oldest light that can be observed with telescopes. It represents the residual glow released approximately 380.000 years after the Big Bang, when the universe cooled enough for protons and electrons to form atoms.
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At that moment, the formation of atoms allowed light to propagate freely through the cosmos. Before that, the universe was opaque, preventing any radiation from traveling great distances.
Astronomers analyze how the polarization of light may indicate new physics.
According to the European Space Agency, cosmic microwave background radiation is the most distant and oldest light that can be detected by telescopes. Therefore, it offers astronomers one of the best opportunities to investigate the birth and evolution of the universe.
This radiation is extremely weak and nearly uniform, but it spreads throughout the known universe. For the most part, its characteristics coincide with predictions from cosmological models currently used in physics.
Even so, some anomalies have been recorded for decades in radiation cosmic background. Among them are phenomena known as the cosmic dipole and the structure nicknamed the axis of evil.
These irregularities indicate that certain aspects of the cosmic microwave background radiation are not yet fully understood. For this reason, astronomers continue to investigate whether new interpretations of the physics may be necessary.
Cosmic birefringence reveals unexpected rotation of light polarization.
In 2020, scientists reported for the first time evidence of a phenomenon called cosmic birefringence. The discovery arose from the analysis of the polarization of light from the cosmic microwave background radiation.
Polarization is the process by which the oscillations of a light wave become restricted to a single plane perpendicular to the direction of propagation. Under normal conditions, this plane remains stable as the light travels through space.
However, by comparing the cosmic microwave background radiation with the light scattered by the dust of the Milky Way, researchers identified signs that the polarization has undergone a slight rotation throughout the history of the universe.
The first study estimated that this rotation was approximately 0,3 degrees. Although this is an extremely small value, it is not predicted by the standard model of physics.
New measurements reinforce the phenomenon studied by astronomers.
A preliminary paper published in September 2025 provided a new estimate for this rotation. Using polarization data collected by the Atacama Cosmological Telescope, scientists calculated an average rotation of 0,215 degrees.
Even though it is lower than the initial estimate, the new measurement is still considered unexpected. According to the researchers, any systematic rotation in the polarization of the cosmic microwave background radiation may indicate as yet unknown physical phenomena.
The team responsible for the study explained that the polarized light from the CMB can be sensitive to processes that violate so-called parity symmetry. This type of effect is not predicted by traditional descriptions of cosmological physics.
According to scientists, interactions between photons and still poorly understood components of the universe could produce this effect. Among the candidates mentioned are fields associated with dark matter and dark energy.
The hypothesis involves particles called axions.
In a new paper released in preprint, researchers suggest that particles called axions may help explain the phenomenon. These hypothetical particles are considered promising candidates for composing dark matter.
According to the study, axion-like particles possess properties that could generate the rotation observed in the polarization of the cosmic microwave background radiation. The proposal involves the interaction between fields associated with these particles.
The team argues that the superposition of two axion-like particle fields with different masses could overcome known limitations such as the washout effect. This combination would allow for reconciling observations with theoretical calculations.
Despite the hypothesis, the researchers themselves state that further studies will be necessary. Future analyses should confirm whether cosmic birefringence truly exists and what the exact intensity of the detected rotation is.
Only with additional measurements will it be possible to determine the impact of this phenomenon on physics and on the standard model that describes the universe. The most recent study was published on the arXiv preprint server and has not yet undergone peer review.