Barred Spiral Galaxies

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  • Author
    Posts
  • #575146
    Alan Thomas
    Participant

    Can anyone give me the latest on how barred spiral galaxies are formed? They seem an unlikely formation.

    #585178
    Daryl Dobbs
    Participant
    #585180
    Alan Thomas
    Participant

    Thanks

    #585181
    Dominic Ford
    Keymaster

    This is still a somewhat contentious question among theorists, but essentially the density waves that create the spiral pattern in spiral galaxies are only stable in the outer parts of a galaxy, beyond a certain radius called in “inner Lindblad resonance”. In the inner parts of the galaxy, different mechanics operate.

    Simulations suggest that in these inner parts, density waves still occur, but they tend to cause material to pile up into a linear feature (i.e. a bar) rather than a spiral pattern. However, the timescale for the bar to appear is quite long, and so young spiral galaxies may not have had time to grow a bar yet, even if their spiral structure is well developed. They may well start acquiring a bar in the future.

    Moreover, when spiral galaxies collide with one another, or have close gravitational encounters, this tends to mess up the delicate spiral structure and bar formation processes and cause them to ultimately become elliptical galaxies.

    Edwin Hubble believed that elliptical galaxies turned into spiral galaxies over time, but we now believe that the opposite is true.

    #585182
    Alan Thomas
    Participant

    Thanks!

    #585183
    David Swan
    Participant

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    #585189
    Alan Thomas
    Participant

    Very nice!

    #585191
    owen brazell
    Participant
    #585215
    Alan Thomas
    Participant

    Cheers!

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