The magnetic field of a spiral galaxy


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Magnetic field of a spiral galaxy
Click for full image.

Using a variety of telescopes, especially the Jansky Very Large Array radio telescope, astronomers have successfully mapped the magnetic field lines of a spiral galaxy seen edge on and 67 million light years away.

The image to the right, cropped and reduced to post here, shows what they have found.

The magnetic field lines extend as much as 22,500 light-years beyond the galaxy’s disk. Scientists know that magnetic fields play an important role in many processes, such as star formation, within galaxies. However, it is not fully understood how such huge magnetic fields are generated and maintained. A leading explanation, called the dynamo theory, suggests that magnetic fields are generated by the motion of plasma within the galaxy’s disk. Ideas about the cause of the kinds of large vertical extensions seen in this image are more speculative, and astronomers hope that further observations and more analysis will answer some of the outstanding questions.

Our understanding of these kinds of gigantic magnetic fields is poor, to put it mildly. This data really only begins the research.

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4 comments

  • Milt Hays, Jr.

    OK, I’m not sure that I want to do this, but…

    Robert cites this from the NARO site:

    “The magnetic field lines extend as much as 22,500 light-years beyond the galaxy’s disk. Scientists know that magnetic fields play an important role in many processes, such as star formation, within galaxies. However, it is not fully understood how such huge magnetic fields are generated and maintained. A leading explanation, called the dynamo theory, suggests that magnetic fields are generated by the motion of plasma within the galaxy’s disk.”

    According to my old college physics, it’s ELECTROmagnetism, and you can’t have one without the other. Likewise the motions of plasma are hypothesized as the origin of such fields.

    Again, I am loathe to even broach this subject, but it all sounds a lot like the “alternative” cosmology of the Thunderbolts Project.

    While a lot of the Thunderbolts adherents seem to be classic “true believers” and don’t seem to tolerate much dissent from the One and Only Holy Faith, it seems to me that they do make some very telling points, particularly about the behavior of comets. See https://www.youtube.com/watch?v=34wtt2EUToo

    That said, you can talk rationally — I hope! — about the role of plasma and EM phenomena in the universe without maintaining the obligatory Velikovsky-inspired belief that one day Jupiter spat out Venus and that it later settled into an almost perfect circular orbit around the sun, etc. But that there is a lot of “crackpottery” here does not mean that they are *totally* wrong in wanting to investigate plasma / EM effects. Likewise, you can — again I hope — advance arguments about how this may be a better model for cometary behavior without being shouted down as a lunatic so long as you can produce credible evidence. Indeed, science used to “work” this way, and back in the day, even astronomers with the credibility of Otto Struve, writing in Sky and Telescope, advocated further research into this.

    Could we at least look objectively at the evidence?

    Milt

  • John

    People see things so differently.

    I thought that link had almost exactly no information. How did they make the image? Why do the field lines look like a kindergartner painted them on?

    What Milt read didn’t occur to me.

  • Edward

    Milt Hays, Jr. noted: “According to my old college physics, it’s ELECTROmagnetism, and you can’t have one without the other.

    The plasma is matter that has some, most, or usually all of its electrons stripped from it. This plasma is the “electro” part. Ionized hydrogen (a proton without its electron) is a common component of the solar wind.

    John asked: “How did they make the image?

    To get high resolution, like this, a radio telescope has to be very large. It can be a large array rather than a single dish antenna, and that is one of the purposes of the Jansky Very Large Array (VLA) radio telescope, with a possible equivalent diameter of 26 miles.
    https://en.wikipedia.org/wiki/Very_Large_Array#Characteristics

  • Edward: I should have noted in my post that the galaxy in this image is from optical telescopes. Jansky provided the info for the magnetic field lines (the white streaks above and below the galaxy’s plane).

    It appears the radio data overlays the optical image, and because much of it is computer generated (as they combine the pieces from the radio array), it has the look of an artist’s impression.

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