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A continuous stream of charged particles is erupting from the center of our galaxy, the Milky Way. This, conclude astronomers on 3 January in Nature, is a by-product of the birth of new stars. The outflow would also seem to play a part in the Milky Way’s magnetic field. One of the authors is astronomer Marijke Haverkorn of Radboud University Nijmegen, also affiliated with Leiden University.

The newly discovered flows of charged particles from the center of the Milky Way is in light blue. The background is a photo of the entire sky on the same scale. The Milky Way is clearly visible. The curve of the stream of charged particles is real, and is not caused by projection effects. Image Credits: radio: E. Carretti (CSIRO); optical: A. Mellinger (Central Michigan University); scientific imager: E. Bressert (CSIRO)

Measurements made using CSIRO’s 64 metre Parkes radio telescope in eastern Australia and published in today’s issue of Nature show that huge flows of charged particles travelling at 1,000 kilometers per second are spewing from the center of our galaxy. ‘That’s fast, even for astronomers’, said Dr Ettore Carretti, team leader at CSIRO. These outflows contain an extraordinary amount of energy – about a million times the energy of an exploding star. The outflows extend 50,000 light-years: half the diameter of the whole of the Milky Way. Seen from Earth, the outflows stretch about two thirds across the sky from horizon to horizon.

Star formation creates magnetic field

According to the researchers – from Australia, the USA, Italy and the Netherlands – the outflow is due to the formation of new stars in the center of the Milky Way. Their conclusion is based on precise measurements of radio waves emitted by the outflow under the influence of the Milky Way’s magnetic field. Many generations of stars forming and exploding over the last hundred million years have left behind flows of radiation in the rotating Milky Way in the form of a corkscrew, and it is these that have now been discovered.

Astronomer Marijke Haverkorn of Radboud University Nijmegen

‘The outflow from the galactic center carries off not just gas and high-energy electrons, but also strong magnetic fields’, explained Marijke Haverkorn, who conducts research into magnetism in the Universe.
‘The new observations help to answer an important question about the Milky Way: how it generates and maintains its magnetic field. We suspect that these outflows have a big part to play in this.’

Earlier measurements now explained

The outflows correspond to the enormous ‘Fermi bubbles’ of gamma radiation detected by the NASA Fermi space telescope in 2010 and published in Nature. Two possible causes of these surprising Fermi bubbles were given at the time: strong star formation or outbursts from the black hole in the center of the Milky Way. ‘Our measurements now tell us that the bubbles are the result of the formation of millions of stars close to the center of the Milky Way’, said Haverkorn.

Because the particles flow perpendicularly from the center of the Milky Way into space, like a wheel axle, there is no threat to the Earth and our Solar System, located some 30,000 light years from the center of the Milky Way.

The research paper: “Giant Magnetized Outflows from the Centre of the Milky Way” was published in Nature on Januari 3, 2013. The Auteurs are: Ettore Carretti, Roland M. Crocker, Lister Staveley-Smith, Marijke Haverkorn, Cormac Purcell, Bryan M. Gaensler, Gianni Bernardi, Michael J. Kesteven, and Sergio Poppi.

Source: Radboud Universiteit Nijmegen, the Netherlands

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