Magnetized Outflows from Center of the Milky Way are Driven by Star-Formation Activity


A false-color image of our Milky Way as seen in a projection that shows the galactic center at the center of the image, the plane of the galaxy stretching across the central band, and the two arc-shaped radio lobes of emission seen extending north and south of the plane. Several of the newly discovered magnetic structures are labeled. Credit: Carretti et al., and Nature

In a newly published study, a team of scientists from the Smithsonian Astrophysical Observatory suggest that the recently discovered twin lobes of gamma-ray emission protruding about 50,000 light-years above and below the plane of our Milky Way galaxy are driven by star-formation activity, not black-hole activity.

Two years ago, CfA astronomers reported the discovery of giant, twin lobes of gamma-ray emission protruding about 50,000 light-years above and below the plane of our Milky Way galaxy, and centered on the supermassive black hole at our galaxy’s core. The scientists argued then that the bubbles were produced either by an eruption from the black hole sometime in the past, or else by a burst of star formation in that vicinity.

It now appears that these giant bubbles of hot gas can be seen at radio wavelengths as well. Writing in the new issue of the journal Nature, CfA astronomer Gianni Bernardi and eight of his colleagues describe finding humongous lobes of radio emission emanating from the Galactic Center. Moreover, the emission is polarized, a general property that electromagnetic radiation can have; some sunglasses take advantage of the fact that reflected sunlight becomes polarized. In the case of radio wavelengths, the explanation for polarization is the presence of strong magnetic fields.

The scientists calculate that the radio lobes, which closely match the gamma-ray lobes in overall dimensions but which contain three ridge-like substructures, are probably polarized by the presence of strong magnetic fields that extend out of the galactic plane in both directions for tens of thousands of light-years, and which contain an energy roughly equivalent to the total current output of the Sun for a time equal to the lifetime of the universe. They argue that the activity is driven by star-formation activity, rather than black-hole activity, and that it originates in a region around the Galactic Center about 650 light-years in size. Not least, the scientists argue that the ridges seen in the magnetically-shaped outflow are the result of several episodes of star-formation that constitute a phonograph-like record of star formation in this region over at least the past ten million years.

Publication: Ettore Carretti, Roland M. Crocker, Lister Staveley-Smith, Marijke Haverkorn, Cormac Purcell, B. M. Gaensler, Gianni Bernardi, Michael J. Kesteven & Sergio Poppi, “Giant magnetized outflows from the centre of the Milky Way,” Nature 493, 66–69 (03 January 2013); doi:10.1038/nature11734

Source: Harvard-Smithsonian Center for Astrophysics

Image: Carretti et al., and Nature

2 Comments on "Magnetized Outflows from Center of the Milky Way are Driven by Star-Formation Activity"

  1. This study of the “Fermi bubbles” is indeed very interesting and points once more in one direction: We have to understand large-scale magnetic phenomena to understand the formation of our universe.

  2. C. Peter O'Connor | May 8, 2013 at 6:08 am | Reply

    Hi, Angus Stone! Hope you are well. The content of this article may be very interesting and informative to ‘You’and may point in ‘One’ direction to You however; ‘I’ am not fooled! And neither should You be! – Or am I too late to suggest that there might be another explanation that can be applied to what is going on at the centres of Spiral Galaxies?

    Try the following on for size! Our entire universe was ‘In-Situ’ ‘BEFORE’ the ‘Bang’ and that spiral galaxies are the pieces of debris flying through Space/Time and emitting their excess ‘Baggage’ from their equators in the form of gas and dust which is naturally drawn backwards in trailing arms.

    The reason for the uncharacteristic density held within the centres of spiral galaxies isn’t because they have ‘Mythical’ ‘Black Holes’ at their cores but all of the heaviest elements ever created. Elements so heavy and so dense that they are driven to emit their excess in the form of radiation, a great deal of which remains trapped within their own electromagnetic potential.

    By the way; If I am right about the way our universe formed and from what, then by virtue Our universe began forming fifteen billion years before the, ‘Bang’ itself took place.

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