Giant magnetic fields in the universe
Astronomers from Bonn and Tautenburg in Thuringia (Germany) used the 100-m radio telescope at Effelsberg to observe several galaxy clusters. At the edges of these large accumulations of dark matter, stellar systems (galaxies), hot gas, and charged particles, they found magnetic fields that are exceptionally ordered over distances of many million light years. This makes them the most extended magnetic fields in the universe known so far.
Radio waves are excellent tracers of relics. The compression of magnetic fields orders the field lines, which also affects the emitted radio waves. More precisely, the emission becomes linearly polarized. This effect was detected in four galaxy clusters by a team of researchers at the Max Planck Institute for Radio Astronomy in Bonn (MPIfR), the Argelander Institute for Radio Astronomy at the University of Bonn (AIfA), the Thuringia State Observatory at Tautenburg (TLS), and colleagues in Cambridge/USA. They used the MPIfR's 100-m radio telescope near Bad Munstereifel-Effelsberg in the Eifel hills at wavelengths of 3 cm and 6 cm. Such short wavelengths are advantageous because the polarized emission is not diminished when passing through the galaxy cluster and our Milky Way. Fig.1 shows the most spectacular case.
|The 100-m radio telescope near Bad Munstereifel-Effelsberg. The observations of polarized radio emission |
from galaxy clusters were performed with this telescope at wavelengths of 3 and 6cm
[Credit: © Norbert Junkes/MPIfR]
The new Effelsberg telescope observations show that the polarization plane of the radio emission from the relics turns with wavelength. This "Faraday rotation effect", named after the English physicist Michael Faraday, indicates that ordered magnetic fields also exist between the clusters and, together with hot gas, cause the rotation of the polarization plane. Such magnetic fields may be even larger than the clusters themselves.
"The Effelsberg radio telescope proved again to be an ideal instrument to detect magnetic fields in the universe", emphasizes co-author Rainer Beck from MPIfR who works on this topic for more than 40 years. "Now we can systematically search for ordered magnetic fields in galaxy clusters using polarized radio waves."
The results are published in the journal Astronomy & Astrophysics.
Source: Max Planck Society [March 21, 2017]