Galaxy Zoo Talk

Why is the 'Sky' Blue

  • berko by berko

    i think I understand, Blue means new, star formation, while Red means old or cooling. Could a reactivating Blackhole be stirring up the Blue stuff.


  • AlexandredOr by AlexandredOr

    Hi ! I think you are right in the first part of your analysis. But really unsure for the stirring blackhole. .


  • ElisabethB by ElisabethB moderator

    If this galaxy has a black hole, which it probably has,than it is most unlikely that the black hole could trigger star formation. Black holes only influence the area very close to them.


  • vrooje by vrooje admin, scientist in response to ElisabethB's comment.

    There's some evidence that some black holes can eventually affect their host galaxies, but they have to be pretty active in order to do so, because as ElisabethB said the black holes themselves are physically quite small and their strong gravity is only evident very near to them. But when they are feeding, they emit radiation, and then they can be very powerful and their emission can extend farther than the galaxy (sometimes). That emission may be able to trigger star formation, or shut it down completely, or both. It's not really clear how that works and it's a very active area of research.

    So -- good question! 😃