An international team of astronomers has gained new insights into the physical conditions prevailing in the gas tail of so-called jellyfish galaxies. They are particularly interested in the parameters that lead to the formation of new stars in the tail outside the galaxy disk. They analyzed, for example, the strength and orientation of the magnetic fields in the galaxy JO206.

Ancla Müller and Professor Ralf-Jürgen Dettmar from Ruhr-Universität Bochum describe their findings together with Professor Christoph Pfrommer and Dr. Martin Sparre from the Leibniz Institute for Astrophysics in Potsdam as well as colleagues from the INAF—Italian national institute of Astrophysics in Padua, Selargius and Bologna in the journal Nature Astronomy from 26 October 2020.

Much of the ‘memory’ of the world and all our digital activities are based on media, hard disks, where the information is encoded thanks to magnetism, by orienting the spin of electrons in one direction or the opposite.

An international team of scientists led by the Italian physicist Stefano Bonetti, professor at Ca’ Foscari University of Venice and the Stockholm University, has managed for the first time to observe the ‘nutation’ of these spins in magnetic materials, i.e. the oscillations of their axis during precession. The measured nutation period was of the order of one picosecond: one thousandth of a billionth of a second. The discovery was recently published by Nature Physics.

The axis of a spin performs nutation and precession, as with any object that revolves, from spinning tops to planets. In this research, physicists observed experimentally that the nutation of the magnetic spin axis is 1000 times faster than precession, a curiously similar ratio to that of Earth.

The comparison of distant atomic clocks is foundational to international timekeeping, global positioning and tests of fundamental physics. Optica l-fibre links allow the most precise optical clocks to be compared, without degradation, over intracontinental distances up to thousands of kilometres, but intercontinental comparisons remain limited by the performance of satellite transfer techniques. Here we show that very long baseline interferometry (VLBI), although originally developed for radio astronomy and geodesy, can overcome this limit and compare remote clocks through the observation of extragalactic radio sources. We developed dedicated transportable VLBI stations that use broadband detection and demonstrate the comparison of two optical clocks located in Italy and Japan separated by 9,000 km. This system demonstrates performance beyond satellite techniques and can pave the way for future long-term stable international clock comparisons.