2 upvotes, 1 direct replies (showing 1)
View submission: Ask Anything Wednesday - Physics, Astronomy, Earth and Planetary Science
The Webb telescope pictures of the distant sky give me an unusual sense of depth compared with previous space photography. Having the extra layer of distant but clearly resolved galaxies seems to help resolve the 3D structure of the universe more clearly, with tendrils of galaxies stretching off into the distance. Is this an accurate interpretation? Is it more prominent with Webb than with previous telescopes?
When we look at astronomy photos that stretch back to the early days of the universe, how exactly does our perspective relate to the age of the light and the expansion of the universe? In photos, does a 13-billion-year-old redshifted galaxy appear in the position of an object 13 billion light years away, or do relativity and the expansion of the universe make it look closer or farther on top of the travel time? It's easy to understand that the distant galaxy is now a lot farther away from us than when its light originally started traveling, but what else happens to inform our perspective of all the incoming light before it finally arrives in the telescope?
Comment by nivlark at 14/09/2022 at 23:14 UTC
2 upvotes, 1 direct replies
Not really. Previous space telescopes like Hubble were still capable of taking deep-field images. JWST can see to greater distances, but the most distant galaxies it can detect appear very small and dim and so contribute little to the overall look of the image. If you find the JWST images more impressive, it's probably just because they are from a newer telescope with better optics and instrumentation.
A galaxy which we see as it was 13 billion years ago is much further away than that now, because the continued expansion of the universe has caused it to keep receding during the light's travel time. This is itself a relativistic effect; another much stranger one is that there is a distance beyond which objects start becoming *larger* as they get further away (because when their light first started travelling, they were closer and so they covered a much larger part of our field of view).