An international research project involving the University of Adelaide has revealed that the magnetic field in the centre of the Milky Way is at least 10 times stronger than the rest of the Galaxy.
The evidence is significant because it gives astronomers a lower limit on the magnetic field, an important factor in calculating a whole range of astronomical data.
Researchers from the Max-Planck-Institute for Nuclear Physics, the University of Adelaide, Monash University and the United States have published their findings in Nature this week.
Dr Roland Crocker, the lead author, and Dr David Jones both worked on the project while based at Monash University and the University of Adelaide’s School of Chemistry and Physics. The two physicists are now based at the Max-Planck-Institute for Nuclear Physics in Heidelberg, Germany.
“This research will challenge current thinking among astronomers,” Dr Crocker says. “For the last 30 years there has been considerable uncertainty of the exact value of the magnetic field in the centre of the Milky Way. The strength of this field enters into most calculations in astronomy, since almost all of space is magnetised,” he says.
Dr Jones says the findings will affect diverse fields, from star formation theory to cosmology.
“If our Galactic Centre’s magnetic field is stronger than we thought, this raises additional questions of how it got so strong when fields in the early universe are, in contrast, quite weak. We know now that more than 10% of the Galaxy’s magnetic energy is concentrated in less than 0.1% of its volume, right at its centre,” he says.
Dr Jones completed his PhD at Adelaide, studying the Galactic Centre magnetic field under the supervision of Dr Raymond Protheroe, Associate Professor of Physics at the University of Adelaide, and Dr Crocker, a former postdoctoral researcher at the University.
“The Milky Way just glows in radio waves and in gamma-rays produced by collisions of energetic particles, and is brightest near its centre. Knowing the magnetic field there helps us understand the source of the radio and gamma-rays better,” says Dr Protheroe.
Related from 2007:
The Black Hole in the Center of the Milky Way Is an Accelerator of Gamma Rays
A new theory rejecting the decaying matter theory
Astronomers have found that the supermassive black hole located in the center of the Milky Way generates the mysterious gamma-ray emission detected in the center of our galaxy.
The mobile magnetic fields around the hole produce high-speed collisions that emit the gamma rays.
Extremely powerful gamma rays, with charges in the tens of tera-electronvolts (1 TeV means 1012 eV) have been picked up recently by ground-based gamma-ray observatories.
Some researchers have proposed them as the result of dark matter particles decaying, but not everybody agrees with this explanation.
The new research comes with//
the idea that the gamma rays are expelled by the most powerful naturally occurring particle accelerator, better than the best atom smashers used by researchers on Earth. The team made calculations based on the particle accelerator scenario, in which protons around the supermassive black hole are constantly hit by the hole’s magnetic fields. These magnetic interactions speed up the protons so much that they are thrown into surrounding gas clouds.
The hole’s magnetic field extends even farther away, so it keeps on kicking the protons to even increased speeds as they travel outwards. “Some of the protons could reach energies of 1000 TeV this way,” said team member Fulvio Melia of the University of Arizona, in Tucson, US. …