The IR source stretching on the right
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What do you guys think about that IR source on the right?
Looks like something passing, though I don't know what it isPosted
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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:
Zooming way out, there is one, but it doesn't seem so bright, and the diffspikes go the wrong way*! 😮
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
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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
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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!
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by JeanTate in response to WizardHowl's comment.
Aaaand here it is (WISE band1):
The light-blue circle is the center of ARG00019tk, where the 'bent' radio source is.
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Oh..it is indeed super bright in the WISE band-1 image.
Do all red giants appear super bright in the IR?
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by JeanTate in response to Ushiromiya Xyrius's comment.
If they're close enough to us, they do 😉
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