[HN Gopher] A dramatic Einstein ring seen by Webb
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A dramatic Einstein ring seen by Webb
Author : programd
Score : 108 points
Date : 2025-04-02 14:32 UTC (8 hours ago)
(HTM) web link (phys.org)
(TXT) w3m dump (phys.org)
| comrade1234 wrote:
| Are diffraction spikes of light not present because everything in
| the picture is a galaxy and not stars? Or do they remove them now
| with processing?
|
| Here's what I mean:
| https://webbtelescope.org/contents/media/images/01G529MX46J7...
| danparsonson wrote:
| "While all stars can create these patterns, we only see spikes
| with the brightest stars when a telescope takes an image."
|
| These distant galaxies are incredibly faint, so I imagine
| that's the reason there are no obvious diffraction effects.
| dylan604 wrote:
| Yeah, the diffraction spikes in Webb/Hubble images are clues
| that those stars are nearby within the Milky Way.
| milleramp wrote:
| Because the aperture isn't made up of nice straight edges.
| rimeice wrote:
| Can someone with the knowledge explain, is the close elliptical
| galaxy actually just the small dot of light in the centre and the
| spiral galaxy is behind it but dramatically magnified by the lens
| effect?
| danparsonson wrote:
| Yes the elliptical galaxy is the fuzzy blob in the middle;
| blended with the galaxy behind, it's difficult to see the
| diffuse outer parts of it. I'm not sure how much the apparent
| size of the spiral is affected by magnification, vs how much is
| just relative size difference. I guess it would be useful to
| know the distance between them.
| rimeice wrote:
| Wow I get the distances aren't shown, but still, the
| magnification is impressive.
| pavel_lishin wrote:
| Yep, although the elliptical galaxy also includes the diffuse
| glow around the small dot of light.
|
| The galaxy behind it is magnified, and also distorted.
| throwawaymaths wrote:
| this should be able to be used to test dark matter theories.
| zehaeva wrote:
| They're not collecting all of this data to make pretty
| pictures, it's going to be used to test all sorts of theories.
| Ones that explain Dark Matter as well.
|
| (I do agree with Angela Collier, youtuber nee physicst, Dark
| Matter is not a theory, it's an observation. We've looked out
| into the universe and have seen something that we call Dark
| Matter that our current theories don't match up with.)
| throwawaymaths wrote:
| it's a theory. when you present multiple observations just
| the fact that you group them together is not a value-free
| action and implies a common cause. calling it an observation
| is a crude and philosophically improper attempt to elevate it
| to a less refutable status.
| zehaeva wrote:
| This feels like you'd say that just because apples fall
| from trees and a bowling ball falls in much the same way
| when tossed off a building, that grouping those things
| together implies a common cause and that we should call
| that cause a theory because we aren't 100% certain that
| they are caused by the same effect.
|
| They could be two different reasons.
|
| I do prefer Occom's razor for these things. We've seen a
| bunch extremely large celestial objects move in ways that
| our models cannot account for with the things that we can
| see. Sure, there could be more than one thing out there
| causing all of those extremely similar effects. But that's
| far less likely than there just being one reason.
| fatbird wrote:
| This is, in fact, part of the support for Dark Matter, both
| with galaxies (the amount of lensing requires the galaxy to
| include a lot of Dark Matter) and between galaxies, where other
| lensing effects occur that can only be explained by filaments
| of Dark Matter between galaxies and galaxy clusters.
|
| This is a great podcast, with episode 6 concentrating
| specifically on Dark Matter and the evidence for it:
| https://podcasts.apple.com/us/podcast/crash-course-pods-the-...
| throwawaymaths wrote:
| no. you can't say it's evidence for dark matter versus any
| given other theory until after you have computed the expected
| metrics created by any alternative theory.
|
| in any case, you can't say it's support for dark matter in
| this specific case without actually running the numbers (what
| are the rotational speeds and what is the bending curvature)
|
| dark matter halos must have a somewhat specific distribution
| that goes beyond the perimeter of the visible galaxy itself.
|
| however the more that i think about it this example is likely
| to be unhelpful. the closer galaxy looks elliptical and most
| dense elliptical galaxies "have no dark matter" (in basic
| MOND this is a phenomenon that falls out if the gravity law).
| We'd really need lensing from a more "normal" looking galaxy.
| fatbird wrote:
| I wasn't saying, as a layman, that this is evidence for
| Dark Matter. I'm saying that the current thinking in
| astrophysics is that this is evidence for Dark Matter.
| Katie Mack, the astrophysicist in the podcast I linked,
| _is_ a reknowned expert, and discusses how running the
| numbers on exactly these things provides evidence for Dark
| Matter, and how alternatives fail.
| throwawaymaths wrote:
| then she is being misleading, at best. To date no
| observed galaxies (versus galaxy clusters) have had the
| arrangement (as is in this image) wherein the galaxy is
| so perfectly in line with a background galaxy and close
| enough to estimate the rotation curves (and the
| background galaxy is of the right disposition to know if
| dark matter halos extend beyond the galaxy and estimate
| by how much space). Without both those factors it's
| really difficult to do a proper correlation of dark
| matter distribution around galaxies and the observed
| light bending.
| fatbird wrote:
| She does not specifially address this scenario. I offered
| the link as a general dive into the evidence behind Dark
| Matter as it relates to lensing.
|
| I regret that now.
| ziddoap wrote:
| > _I regret that now._
|
| I, on the other hand, am thankful for it. I love watching
| Anton Petrov, PBS Space Time, and various other experts
| and communicators in anything space-related. This looks
| like a great podcast that slipped me by, so I appreciate
| the link.
| perihelions wrote:
| https://esawebb.org/images/potm2503a/ ( _" Spying a spiral
| through a cosmic lens"_)
|
| https://www.esa.int/ESA_Multimedia/Images/2025/03/Webb_spies... (
| _" Webb spies a spiral through a cosmic lens"_)
|
| Some clarifying context not present in this OP (phys.org): this
| is a composite of Hubble visible-light images with Webb data.
| dylan604 wrote:
| Has someone come up with a way to de-warp an object seen as an
| Einstein ring? I thought I had read someone doing this, but maybe
| it was they were _trying_ to do this. Maybe it was during the
| discussion on using Sol as a gravitational lens like this?? Seems
| like some interesting math to put the image in TFA back into the
| shape of a galaxy.
| rf15 wrote:
| Dewarping it mathematically should be fairly easy if the lens'
| gravitational field is sufficiently uniform. Problem is more
| the amount of detail we actually have in these pictures to
| expand the most compressed parts.
| dylan604 wrote:
| I wonder if correctly dewarping would help get a measurement
| of distance of the lensing object. Would that then be able to
| help recalibrate/confirm our understood distances/scale/etc?
| timdiggerm wrote:
| > Of course, this image is only possible because of our vantage
| point. Astronomers in other galaxies wouldn't catch such a
| wondrous image.
|
| Well no, but they probably would catch other wondrous images we
| can't catch due to our vantage point.
| kohbo wrote:
| > beauty is not only in the eye of the beholder, but also where
| that beholder is.
|
| I love this
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