OK it is really late here, but today's reveal of the first JWST image of the galaxy cluster SMACS-0723 was amazing, and I am still digesting it. There is so much stuff going on, it is absolutely breathtaking!

Just to get an idea of what an improvement this is over Hubble, over at The Robot Report, they show this beautiful side-by-side view of the previous best image taken with Hubble, and tonight's result. It's wild.

The features (galaxies?) that appear stretched out and bent, is that gravity lensing, or mirror distortion, or is “bent elliptical” a regular galaxy shape, or…? (or is that a question we hope JWST can help answer?)
I see some of the effect in the Hubble image (so probably not a mirror thing), but it’s so much more apparent in the new one, there seems to be an overall pattern to it?


@silvermoon82 What you see is (mostly) strong gravitational lensing, and there is a lot of that going on here. As you say yourself, there is already quite a bit of it in the Hubble image, but we see so much more of it with JWST. We kind of suspected this would be the case beforehand - the better contrast simply means we can see fainter galaxies, so many more things such as faint arcs like these are popping out.

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@silvermoon82 But one thing is suspecting it, another thing is seeing it. The more you look at the JWST image, the more you realize that they are just everywhere.

@silvermoon82 It is also the hope that deep observations of these lensing clusters with JWST will help us find some of the very earliest galaxies in the history of the Universe. Many of these are so small and faint they are on the edge of what even JWST can see. But if one of them happens to lie between one of these arcs, we could be in luck and get a direct view of the completely new-born Universe.

Oh, wow - that’s exciting!
So is that the same sort of technique as the Hubble Deep Field image, but we’d point the telescope at the middle of these arcs?

@silvermoon82 Something like that. The same idea has been tested with Hubble, but JWST will just have way more muscle to do the job.

Funny enough, the most distant galaxies we know today were actually not found this way, but without lensing. That is because only a small fraction of the sky is behind a lensing cluster, so it's a numbers game. If there happens to be one of the first galaxies in the right place, the lensing will be immensely helpful, but if we don't have this kind of luck, it will not help much.

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