Cosmic Mystery: Astronomers Spot Magnetic Field Surrounding Distant Galaxy

Observations using the Karl G. Jansky Very Large Array (VLA) revealed large magnetic structures.

The universe truly is a strange place. Scientists at the Max Planck Institute for Radio Astronomy have spotted a unique cosmic phenomenon: the experts have recently discovered a powerful shifting magnetic field around the galaxy NGC 4631, a spiral galaxy also known as the Whale Galaxy or Caldwell 32.

Located around 25 million light-years from Earth in the constellation Canes Venatici. Its size is 80,000 light-years in diameter which means it isn’t that much smaller compared to our own galaxy, the Milky Way.

The astronomers spotted the magnetic field surrounding the galaxy using the Karl G. Jansky Very Large Array (VLA), a centimeter-wavelength radio astronomy observatory located in central New Mexico.

“This is the first time that we have clearly detected what astronomers call large-scale, coherent, magnetic fields far in the halo of a spiral galaxy, with the field lines aligned in the same direction over distances of a thousand light-years. We even see a regular pattern of this organized field changing direction,” explained Marita Krause, of the Max-Planck Institute for Radioastronomy in Bonn, Germany.

Composite image of the galaxy NGC 4631, the Whale Galaxy, revealing large magnetic structures. Image Credit: NRAO / VLA.
Composite image of the galaxy NGC 4631, the Whale Galaxy, revealing large magnetic structures. Image Credit: NRAO / VLA.

The image, obtained by an interatrial team of astronomers part of a project dubbed the Continuum HAlos in Nearby Galaxies — an EVLA Survey (CHANG-ES), shows a large-scale, coherent magnetic field that is generated by dynamo action deep within the galaxy and spirals outward in the form of supermassive magnetic ropes, which are seen perpendicular to the disk.

“We are a little bit like the blind men and the elephant, since each time we look at the galaxy in a different way we reach a different conclusion about its nature! However, we seem to have one of those rare occasions where a classical theory, about magnetic generators called dynamos, predicted the observations of NGC 4631 quite well. Our dynamo model produces spiraling magnetic fields in the halo that are a continuation of the normal spiral arms in the galaxy’s disc,” revealed Richard Henriksen, of Queen’s University.

However, to further understand the motion and structure of the galaxy’s magnetic field further observations and studies will be needed.

The image obtained by experts was produced using data combined from several observations with the VLA’s giant dish antennas arranged in different configurations that eventually allowed experts to have a peek at both larger structure and finer details inside the galaxy’s core.

Researchers analyzed the naturally-emitted radio waves coming from the galaxy which allowed them to reveal the magnetic field as well as the direction in which it flows.

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