Magnetic field detected between dwarf galaxies

The Large and Small Magellanic Clouds are connected to each other by a Galactic Bridge. Astronomers have now detected a magnetic field associated with this gaseous filament for the first time.

The Large and Small Magellanic Clouds appear in the sky above the Australia Telescope Compact Array in New South Wales.
Image: Mike Salway

Astronomers have detected a magnetic field between the Milky Way's two nearest galactic neighbours for the first time.

Our Galaxy is orbited by two dwarf galaxies known as the Large and the Small Magellanic Clouds, located 160,000 and 200,000 lightyears away respectively. There is a filament of gas stretching 75,000 lightyears between the two galaxies, and a magnetic field associated with this Galactic Bridge has been detected for the first time.

“There were hints that this magnetic field might exist, but no one had observed it until now,” says Jane Kaczmarek of the University of Sydney, lead author of the study.

An image of the Large and Small Magellanic Clouds captured with an SBIG STL-11000M CCD camera and Canon prime lens. The image was captured in black and white monochrome to help reduce noise in the final image. Colour details of the galaxies were then overlaid. Find out more about the imaging technique here.
Credit: Y. Beletsky (LCO), D. Martinez-Delgado/ESO

The team detected the magnetic field by observing radio signals from distant galaxies. These signals act as background torches that shine through the bridge. The magnetic field changes the polarisation of the radio signals and this provides information as to the magnetic field's properties.

The magnetic field is about one millionth of the strength of Earth’s. Studying it could reveal whether it was generated from within the bridge or was taken from the dwarf galaxies when they interacted to form the structure.

“In general, we don’t know how such vast magnetic fields are generated, nor how these large-scale magnetic fields affect galaxy formation and evolution,” says Kaczmarek. “The LMC and SMC are our nearest neighbours, so understanding how they evolve may help us understand how our Milky Way Galaxy will evolve.”


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