Enormous outflows of charged particles from the centre of our Galaxy, stretching more than halfway across the sky
and moving at supersonic speeds, have been detected and mapped with CSIRO's 64-m Parkes radio telescope.
Corresponding to the "Fermi Bubbles" found in 2010, the recent observations of the phenomenon were made by a team
of astronomers from Australia, the USA, Italy and The Netherlands, with the findings reported in the January 2
issue of Nature.
"There is an incredible amount of energy in the outflows," said co-author Professor Lister-Staveley-Smith from The
University of Western Australia node of the International Centre for Radio Astronomy Research in Perth and Deputy
Director of the ARC Centre of Excellence for All-sky Astrophysics (CAASTRO).
"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 (a dying star)."
From top to bottom the outflows extend 50,000 light-years [five hundred thousand million million kilometres] out of
the Galactic Plane. That's equal to half the diameter of our Galaxy (which is 100,000 light-years -- a million million
million kilometres -- across).
Click on image to enlarge
This shows the “geysers” (in blue) shooting out of the Milky Way.
"Our Solar System is located approximately 30,000 light-years from the centre of the Milky Way Galaxy, but we're perfectly
safe as the jets are moving in a different direction to us," said Professor Staveley-Smith.
Seen from Earth, but invisible to the human eye, the outflows stretch about two-thirds across the sky from horizon to
They match previously identified regions of gamma-ray emission detected with NASA's Fermi Space Telescope (then-called
"Fermi Bubbles") and the "haze" of microwave emission spotted by the Wilkinson Microwave Anisotropy Probe (WMAP) and
Planck Space Telescope.
"Adding observations by the ground-based Parkes radio telescope to those made in the past by space telescopes finally
allows us to understand how these enormous outflows are powered," said Professor Staveley-Smith.
Previously it was unclear whether it was quasar-like activity of our Galaxy's central super-massive black hole or star
formation that kept injecting energy into the outflows.
The recent findings, reported in Nature, show that the phenomenon is driven by many generations of stars forming and
exploding in the Galactic Centre over the last hundred million years.
Click on image to enlarge
Galactic Geysers. A view of the 'galactic geysers' that have been mapped. Click for largest resolution.
Credit: ESA Planck Collaboration (Microwave) NASA DOE Fermi LAT, Dobler et al. Su et al. (Gamma Rays).
"We were able to analyse the magnetic energy content of the outflows and conclude that star formation must have happened
in several bouts," said CAASTRO Director Professor Bryan Gaensler.
Further analyses of the polarisation properties and magnetic fields of the outflows can also help us to answer one of
astronomy's big questions about our Galaxy.
"We found that the outflows' radiation is not homogenous but that it actually reveals a high degree of structure --
which we suspect is key to how the Galaxy's overall magnetic field is generated and maintained," said Professor Gaensler.