In our vast universe, there are unimaginably big things. The biggest gravitationally bound structures in observable Universe are galaxy clusters, with a typical extent of about 10 million light years or larger. Clusters are the host of hundreds of galaxies, stellar systems, charged particles, intergalactic gas – all embedded in large halos of dark matter. Given that clusters drifting through space, galaxies may occasionally collide. Although collisions do not cause contact between stars and planets due to huge space between them, these collisions generate a magnetic field, created from the gas and particles.

Astronomers have spotted one such a field, which is, it turns out, the largest magnetic field ever seen. Moreover, it is expected that many of these magnetic fields could be bigger than the clusters themselves.

The 100-m radio telescope near Bad Münstereifel-Effelsberg used in this study. Image credit: Norbert Junkes/MPIfR

Galactic ‘sausage’ of magnetism

Astronomers from Bonn and Tautenburg in Thuringia (Germany) used the 100-m radio telescope at Effelsberg to observe several galaxy clusters. They focused their observations on so-called collision relics – a great mixture of gas, dust and charged particles blended after collisions. The best way to capture relics is to take images in radio waves, which can reveal large-scale magnetism. After taking the images of a galaxy cluster called – CIZA J2242+53, they noticed relics in the shape of a sausage. Astronomers tend to give a name to relics according to their shape.

The picture of a galaxy, located 2 billion light-years from Earth, shows radio waves ( green), X-rays (red). In the background is visible light. Image credit: M. James Jee et al./The Astrophysical Journal

The astronomers have discovered that “sausage” relics generates the giant magnetic field. Its strength is similar to the Milky Way’s, dozen times wider than our galaxy and it’s highly polarized. Study lead author Maja Kierdorf from the Max Planck Institute for Radio Astronomy said: “We discovered the so far largest ordered magnetic fields in the universe, extending over 5-6 million light years. Such magnetic fields may be even larger than the clusters themselves“.

The image shows “sausage” relics and intensity of its radio wave emission at a wavelength of 3 cm. Red color represents most intense emission, while blue is weaker. Image credit: M. Kierdorf et al., A&A 600, A18

Astronomers discovered about 70 radio relics so far. Thanks to this particular “sausage relics” findings with a use of Effelsberg radio telescope, they can systematically search for ordered magnetic fields in galaxy clusters using polarized radio waves.