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Agreed! In the SMACS 0723 image, there is a red spiral galaxy near the top right which is effectively not present in the HST image because it was redshifted out
by nacogo 4y ago
Agreed! In the SMACS 0723 image, there is a red spiral galaxy near the top right which is effectively not present in the HST image because it was redshifted out of the spectrum. This implies it's one of the galaxies receding the fastest from us in the image right? And therefore also among the oldest and farthest away?
https://blog.wolfd.me/hubble-jwst/ https://blog.wolfd.me/hubble-jwst/
- lisper 4y agoYes, exactly right. (AFAIK, IANAA)
- t3estabc 4y ago
- supernova87a 4y agoYes, well 2 possible effects: 1) as you said, its flux is predominantly in the IR 2) it could have been fainter than the sensitivity of the HST instruments but now seen because of the sensitivity of JWST But given that it appears so bright in the JWST image similar to other nearby galaxies that do appear in the HST image, your bet on #1 seems reasonable. Also there is another point: rather than a highly redshifted galaxy it could be a very dusty nearby galaxy (also appearing very red) but if I remember right, that would have a slightly different signature. Dusty galaxies often aren't entirely dusty and have "lanes/channels/streaks" of dust that are interspersed among normal stellar regions, so if it were that, you would be seeing some bright spots outside the infrared. But this one has the shape of a normal galaxy but red all over, suggesting something affects the whole galaxy -- i.e. redshift.
- importantbrian 4y agoIsn't there a 3rd possibility that the galaxy is quenched leaving only redder stars?
- iampivot 4y agoIsn't one way to detect redshift to check if there's absorption of certain frequencies due to the light passing through matter on the way here? The absorption will be redshifted as well?
- mortenjorck 4y agoRelated question: to confirm, some of the additional detail we’re seeing in the JWST images is in fact IR that has been “hue clamped” into the visible spectrum?
- soulofmischief 4y agoIt's all IR. It's color-mapped over RGB, but the sensors are IR.
- wlesieutre 4y agoNIRCam’s range starts at 0.6 microns (600 nm) so picks up a little bit of the red end of our visible range. But it definitely can’t differentiate a range of human visible colors.
- rkagerer 4y agoDidn't the observed light shift into IR wavelengths due to the expansion of space over the last billions of years while it traveled to us? Do the recolored images have any relation to what the original view would have looked like, or is it just arbitrary "artistic license"?