Monster outflows of charged particles from the centre of our galaxy, stretching more than halfway across the sky, have been detected and mapped with CSIRO’s 64-m Parkes radio telescope in eastern Australia.
The outflows were detected by astronomers from Australia, the USA, Italy and The Netherlands.
“These outflows contain an extraordinary amount of energy -- about a million times the energy of an exploding star,” Dr. Ettore Carretti, study leader from CSIRO, said.
But the outflows pose no danger to Earth or the solar system.
The speed of the outflow is supersonic, about 1000 kilometers a second.
“That’s fast, even for astronomers,” Dr. Carretti said.
“They are not coming in our direction, but go up and down from the galactic plane. We are 30,000 light-years away from the galactic center, in the plane. They are no danger to us,” Carretti said.
From top to bottom the outflows extend 50,000 light-years out of the galactic plane, which is equal to half the diameter of our galaxy.
Seen from Earth, the outflows stretch about two-thirds across the sky from horizon to horizon.
The outflows correspond to a “haze” of microwave emission previously spotted by the WMAP and Planck space telescopes and regions of gamma-ray emission detected with NASA’s Fermi space telescope in 2010, which were dubbed the “Fermi Bubbles”.
The WMAP, Planck and Fermi observations did not provide enough evidence to indicate definitively the source of the radiation they detected, but the new Parkes observations do.
“The options were a quasar-like outburst from the black hole at the galactic center, or star-power -- the hot winds from young stars, and exploding stars,” team member Dr. Gianni Bernardi from the Harvard-Smithsonian Center for Astrophysics, in Cambridge, Massachusetts, said.
“Our observations tell us it’s star-power,” Bernardi said.
In fact, the outflows appear to have been driven by many generations of stars forming and exploding in the galactic centre over the last hundred million years.
The key to determining this was to measure the outflows’ magnetic fields.
“We did this by measuring a key property of the radio waves from the outflows -- their polarization,” team member Dr. Roland Crocker from the Australian National University said.
The new observations also help to answer one of astronomers’ big questions about our galaxy: how it generates and maintains its magnetic field.
“The outflow from the galactic centre is carrying off not just gas and high-energy electrons, but also strong magnetic fields,” team member Dr. Marijke Haverkorn from Radboud University Nijmegen in The Netherlands said.
“We suspect this must play a big part in generating the galaxy’s overall magnetic field,” Haverkorn added.
The study has been recently published in Nature.