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Out of the Galactic Plain

By Stephen Luntz

Vast jets of charged particles have been mapped escaping the galactic plane, confirming observations from space telescopes.

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In 2010 the Fermi Gamma-ray Space Telescope found evidence of what were called “Fermi Bubbles” – areas of high-energy particles apparently travelling away from the galactic plane. While it was thought that these bubbles might be originating from the centre of the galaxy, their distance and size could not be established.

Now the Centre of Excellence for All-Sky Astrophysics (CAASTRO) has used the Parkes radiotelescope to measure these distances by detecting changes to the polarisation of radio waves emitted by these particles as they pass through clouds of gas between us and the emission site.

“We can see there is a lot of gas between us and the bubbles, and much more as we go to the plane of the galaxy,” says CAASTRO’s Deputy Director, Prof Lister Staverley-Smith. “This is what we would expect if we are a long way from the source. We can’t place it exactly at the centre of the galaxy, but it is at least halfway there.”

The outflows extend for 50,000 light years. “The source of the energy has been somewhat of a mystery, but we know there is a lot there – about a million times as much energy as a supernova explosion,” Staverley-Smith adds. Proposed sources are the gas jets surrounding the supermassive black hole at the centre of the galaxy and the star formation processes nearby. “We think the latter is more likely,” says Staverley-Smith.

The...

The full text of this article can be purchased from Informit.