January 2, 2013
A view of the
'galactic geysers' that have been mapped.
Credit: ESA Planck
NASA DOE Fermi LAT,
Dobler et al. Su et al. (Gamma Rays).
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 today’s 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
“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
kilometers] 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 kilometers - across).
“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 horizon.
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
“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
hole or star formation that kept injecting energy into the outflows.
The recent findings, reported in Nature today (Giant
Magnetized Outflows from The Centre of The Milky Way), show that the
phenomenon is driven by many generations of stars forming and
exploding in the Galactic Centre over the last hundred million
“We were able to analyze 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 polarization
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.
The research was led by Dr Ettore
Carretti from the Commonwealth Science and Industrial Research
Professor Lister Staveley-Smith
ICRAR The University of Western Australia, and CAASTRO
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