Galactic Geysers Of A Titanic Scale Powered By Star Explosions
Extraordinarily large jets of charged particles exploding from the center of the Milky Way at supersonic speeds were somewhat recently discovered. And now, researchers think that they know what is causing them, “the phenomenon is driven by many generations of stars forming and exploding in the Galactic Centre over the last hundred million years.”
“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).”
When measured from top to bottom, the outflows stretch about 50,000 light-years out of the Galactic Plane, which is about half the diameter of the Galaxy. When observed from the Earth (invisible to the human eye) they extend around 2/3 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 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.
It had been previously unclear what exactly was powering the jets, maybe quasar-like activity, or a super-massive black hole, or extreme levels of star formation.
“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.”
“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.
Image Credits: ESA Planck Collaboration (Microwave) NASA DOE Fermi LAT, Dobler et al. Su et al. (Gamma Rays);