The Solar System could move in space three times faster than previously measureda fact which if confirmed could open a crack in the standard model of cosmology, which explains the large-scale behavior of the universe. This is stated by a new study published in the journal Physical Review Lettersin which a team of astrophysicists – led by astrophysicist Lukas Bohme – has “counted” the expected number of radio sources in different directions in the sky, finding one significant discrepancy with what is predicted by the standard model of cosmology. Hence the conclusion about the speed of motion of the Solar System, which is used to accurately measure the expansion speed of the Universe.
The details of the study
The Universe, on scales from hundreds of millions of light years upwards, appears homogeneous and isotropici.e. its statistical properties are uniform and do not show privileged directions. However, we we are not at rest inside it, but we move in a certain direction with a certain speed on the edge of the Solar System. This creates a apparent anisotropy call dipole which leads to a apparent difference in the distribution of matter between the direction in which we move and the opposite one. A simplistic analogy is the following: suppose you are initially stationary in a room, with no air movement, a condition similar to that of homogeneity and isotropy. If you now start moving quickly in one direction, you will feel the air “pressing” your face, creating an effect of more air in the direction of motion than in the opposite direction.
A similar effect occurs when considering the distribution of sources, in this case sources of radio waves in the Universe. If we were still we would see perfect homogeneity and isotropy, but our movement as part of the Solar System in space generates a dipole effect which gives rise to a excess of sources detected in the direction of motion and a defect in the opposite one. This apparent effect must be considered when making measurements of the large-scale distribution of the Universe since it introduces a false effect of breaking homogeneity and isotropy.
In the article led by the astrophysicist Lukas Böhme from the University of Bielefeld, astronomers measured the distribution in various celestial directions of the radio wave sources detected by the three radio telescopes NVS, RACS-low and LoTSS-DR2. These radio sources are primarily created by the injection of energy into the interstellar medium by the jets of relativistic particles ejected from supermassive black holes at the centers of high-mass galaxies. There are a lot of these items shining in the radio waves and so they are easily identifiable and accountablei in different directions of space.
It is not the first time that these objects have been counted over large celestial areas, but the study in question uses one innovative statistical technique which takes into account the fact that what may appear to be two different but close objects are in reality structures belonging to the same object, which causes a remodulation in the number of sources detected. The use of this technique made it possible to achieve the most accurate measurement of the dipole of radio counts, i.e. of this effect of excess counts in the direction of motion of the Solar System. The scientists thus discovered that although the dipole is aligned in the direction of the previous measurements, its amplitude is a factor of three larger than expectedthat is, aiming for one three times greater speed of the Solar System than expected.
If confirmed by independent measurements, this it would undermine the standard cosmological model and the fundamental assumptions about the large-scale structure of the universe which is assumed to be homogeneous and isotropic. A review of the speeds of motion of the Solar System would also lead to review the speed at which the Universe expandssince the motion of the Solar System is a systematic speed that must be “corrected” in order to determine the exact expansion rate.
What are the alternative explanations?
A revisitation of the cosmological model it’s not the only explanation to the excess number of radio sources found by the authors. There are other possible explanations unexpected contaminations from radio sources in the local Universe, systematic errors due to the different calibrations to which the three different radio telescopes used are subjected or synchrotron radio emission from our galaxy. The latter consists in the emission of electromagnetic radiation generated by electrons moving at speeds close to the speed of light within interstellar magnetic fields that permeate the Milky Way.
If the excess was real and cosmologicalwould have profound implications: either our surroundings are more “special” than expected, or the assumptions of isotropy/homogeneity they need to be reviewed. If instead it is of origin astrophysicsthen the study will help us better understand the distribution and evolution of radio sources in our cosmic neighborhood. The good news is that the next large radio sky mapping projects, such as LoTSS-DR3, RACS-high, EMU and, above all, lo Square Kilometer Array they will put this anomaly under the lens to “confirm or overturn the result”.
