Radio Galaxy Zoo Talk

The IR source stretching on the right

  • Ushiromiya_Xyrius by Ushiromiya_Xyrius

    What do you guys think about that IR source on the right?
    Looks like something passing, though I don't know what it is

    Posted

  • JeanTate by JeanTate in response to Ushiromiya Xyrius's comment.

    Normally these sorts of features are 'diffraction spikes', caused by the support structures which hold the secondary mirror in place and a really bright star (offstage, upper right); they appear as 'compass points' around bright stars.

    However, in this case there doesn't seem to be such a bright star nearby, as seen in SDSS:

    enter image description here

    Zooming way out, there is one, but it doesn't seem so bright, and the diffspikes go the wrong way*! 😮

    enter image description here

    Maybe one of the brighter SDSS stars - in the upper right quadrant - is super-bright in the IR, so creates giant diffspikes?

    *the SDSS and WISE diffspikes do not, necessarily, have the same orientation; however the IR ones clearly come from the top right, not the bottom right

    Posted

  • Ushiromiya_Xyrius by Ushiromiya_Xyrius

    Ohh, I see...the diffraction spikes in IR is actually just like that in the visible wavelength (only different in source)?
    Thank you! Great explanation!

    Posted

  • WizardHowl by WizardHowl

    The star causing the diffraction spike is TYC 2944-689-1. This is some way off - you have to zoom out a couple more steps and SDSS shows it as a bright red star only just within the survey.

    The reason it is contaminating the image from so far away is, as JeanTate has guessed, that it is super-bright in IR. Although listed in the visual V band as just 9.89mag (which is enough to saturate SDSS in the visual), in the near-infra-red J,H and K bands it is about 0 magnitude! WISE band 1, where the RGZ infra-red images come from has a longer wavelength still and this star may well be in the negative magnitudes from its perspective. It is a red giant and part of the reason it is so bright in IR is not just its temperature but its size - stars like this can have radii larger than that of Earth's orbit around our Sun!

    Posted

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

    Aaaand here it is (WISE band1):

    enter image description here

    The light-blue circle is the center of ARG00019tk, where the 'bent' radio source is.

    Posted

  • Ushiromiya_Xyrius by Ushiromiya_Xyrius

    Oh..it is indeed super bright in the WISE band-1 image.

    Do all red giants appear super bright in the IR?

    Posted

  • JeanTate by JeanTate in response to Ushiromiya Xyrius's comment.

    If they're close enough to us, they do 😉

    Posted