(ORDO NEWS) — A team of researchers from several institutes in China and two institutes in Germany analyzed data collected with the Event Horizon Telescope (EHT) and ruled out the existence of axions in a certain mass range around the black hole of the M87 galaxy.
Axions were first proposed in the 1970s. to explain the lack of antimatter in the universe. These particles were also considered as candidates for the role of dark matter particles. Unfortunately, no one has yet been able to confirm their existence.
Instead, physicists continued to look for circumstantial evidence of their presence. In this new study, scientists turned their attention to another hypothesis – according to which axions gather into clouds around black holes.
Until now, scientists have not been able to test this hypothesis because they have not had images of the polarization of light emitted in the vicinity of a black hole.
But the situation changed last year when the EHT (a network of radio telescopes located around the world) took pictures of the black hole of the M87 galaxy and published them in the public domain.
According to the theory, a cloud of axions around a black hole changes the polarization of light emitted in its vicinity, causing fluctuations. In the new study, the authors analyzed data collected by the EHT observatory in search of such fluctuations.
To do this, the team had to filter out all other possible sources that could cause polarization fluctuations. After completing this task, the authors came to the conclusion that the residual level of fluctuations excludes the possibility of the presence of ultralight axions in the cloud.
The methods used by the authors are also applicable to the search for axion-like particles in the vicinity of other black holes, such as the central supermassive black hole of the Milky Way – which will become one of the new scientific targets of the EHT observatory.
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