Galaxy Zoo Talk

How many arms does this galaxy have?

  • Capella05 by Capella05 moderator

    I am not too sure how many spiral arms this galaxy has? Do I only count the arms that directly connect to the core?

    Thanks šŸ˜ƒ


  • Capella05 by Capella05 moderator

    This discussion is part of the How To: Get the best out of Talk thread, so it is a somewhat rhetorical question. šŸ˜ƒ

    But I would be really interested to hear how many arms you think this spiral has šŸ˜ƒ


  • JeanTate by JeanTate in response to Capella05's comment.

    It's a great question, with quite some importance.

    If I recall correctly, the arms in spirals are treated as logarithmic spirals (so rings are clearly not arms!), when de-projected. The idea of distinct arms doesn't really work with flocculent spirals (too many, too indistinct).

    Here's a zoomed in DR8 image:

    enter image description here

    It's not clear - to me, at least - if there's an incomplete inner ring (connecting the ansae, at the ends of the bars), or if there's a small arm. Outside that, I count five arms, plus one anomaly (on a line between the nucleus and the blue star to the right, there's something which looks like an arm that's close to perpendicular to that line; if so, it make almost a right-angle with the arm at its apparent base).

    Hope that helps! šŸ˜ƒ


  • ElisabethB by ElisabethB moderator

    Well, actually it is not. šŸ˜„

    Some will say four, others will say five. And others will say something else. And just the fact that people will mention a different nĀ° of arms is useful. So just go for your gut feeling ! šŸ˜„

    Btw : Happy hunting ! šŸ˜„