Looking into the universe in June 2022
July 11, 2022 6:40 PM   Subscribe

Today NASA published the first image captured by the James Webb Space Telescope. That makes this a fine day to catch up on all of the other ways people and our machines are exploring space.

Around the sun Two probes, the European Space Agency (ESA)/NASA Solar and Heliospheric Observatory and NASA's Solar Dynamics Observatory, captured a vast solar eruption.

Towards Mercury The ESA/Japan Aerospace Exploration Agency (JAXA) BepiColombo probe conducted its second flyby of the solar system's innermost planet.

On and around the Earth Virgin Orbit orbited satellites after a nighttime launch. SpaceX managed the feat of launching and landing three missions in a day and a half. NASA is concerned about Starship damaging its launching pad. The American military's secretive robot shuttle, X-37B, set a new record: 781 days in space.

An amateur space fan tracked down a 2021 Chinese rocket explosion. A Chinese rocket deployed a large "sail" to reduce chances of creating space junk.

Taikonauts on the Tianhe space station prepared for a new module, Wentian, to be attached. The International Space Station (ISS) tried to use a Cygnus freighter for attitude correction. Roscosmos published a photo of cosmonauts on the ISS holding the Luhansk republic's flag; NASA criticized the move.

Crossing Earth's orbit, but far from where the Earth actually is, the very large comet C/2017 K2 is racing towards the sun.

To and on the Moon NASA's CAPSTONE (Cislunar Autonomous Positioning System Technology Operations and Navigation Experiment) probe overcame a glitch on its unusual, slow course to the moon. NASA's administrator expressed concerns that China might lay claim to parts of the moon.

China's Chang'e rover found evidence of water, twice. Ars Technica obtained some NASA Artemis planning materials.

Near the Earth's L2 point The ESA approved plans to launch a Comet Interceptor mission, which will lurk at L2, ready to be hurled at a chosen incoming comet. Webb is starting to do its work.

On, around, to, and from Mars The China National Space Administration published images of Mars taken by the Tianwen-1 orbiter. The Perseverance rover, a bit battered by pebbles, spotted one perfectly balanced rock. The ESA updated Windows 95 running on the Mars Express orbiter. A leading Chinese rocket designer said he expected that nation to return a Mars sample to Earth by 2031.

Asteroids NASA announced a delay in its Psyche asteroid probe launch.

The galaxy The ESA published data on almost 2 billion Milky Way stars. Several scientists explored ways liquid water might exist on "super-Earths."
posted by doctornemo (163 comments total) 80 users marked this as a favorite
 
Download the full-res TIF(26mb) and PNG here(28mb) here.
posted by adept256 at 6:45 PM on July 11, 2022 [12 favorites]


The circular smears are due to gravitational lensing, meaning light is being magnified by something massive between the source and the telescope. The magnification here is beyond JWST's native capacity. Truly the most distant things we've ever seen. We are seeing close to 13.8 billion years ago.

This has been in the making for decades, so much could have gone wrong, there were so many points of failure. Everything has been leading up to this moment.

WOOOOOOO!
WE DID IT!
SCIENCE!
FUCK YEAH!

posted by adept256 at 6:53 PM on July 11, 2022 [64 favorites]


Judging by that first link, the universe looks a hell of lot more like the opening titles of 1980s Doctor Who than I would've expected. The constellation shaped like Peter Davison's face must be in there somewhere...
posted by Ursula Hitler at 6:54 PM on July 11, 2022 [19 favorites]


My father in law worked on the camera optics. He’s retired now but just pleased as punch.
posted by Abehammerb Lincoln at 6:59 PM on July 11, 2022 [50 favorites]


I feel the same optimism watching this that I did watching the shuttles go up as a child.

We're still here, and we're still capable of miracles.
posted by mhoye at 7:10 PM on July 11, 2022 [4 favorites]


BepiColombo probe conducted its second flyby of the solar system's innermost planet.

BepiColumbo: Just one more thing....it's probably not important, but I was just wondering if you could recommend anything at the restaurant you were eating at the night Vulcan was murdered. You see, my anniversary is coming up and Mrs. BepiColumbo has always wanted to eat there, but I don't know, it's all fancy food and I wouldn't know what to order....
posted by RonButNotStupid at 7:11 PM on July 11, 2022 [24 favorites]


NASA published
The ESA published

In the Earthbound Pedant Department: ESA and NASA are both word acronyms, no definite article required. Per ESA's social media intern:
Do people pronounce your name incorrectly? If it's an acronym, you might get that a lot 🤔

Like ESA for example 😉

We're 'ESA', pronounced 'EE-SAH'.

And definitely NOT 'The E.S.A' 😠

(but 'the European Space Agency' is OK😉)
posted by zamboni at 7:47 PM on July 11, 2022 [6 favorites]


Today is a great day to subscribe to Oxford astrophysicist Dr. Becky if you haven't already! She has a great video about scientific data analysis from JWST
posted by lock robster at 7:53 PM on July 11, 2022 [12 favorites]


So glorious to see. One of the few sources of optimism in this naturally pessimistic brain. Now, if only I could convince about 60 million people to put their faith in this science the way they do having an MRI, flying in a plane, or even charging their various devices.
posted by barrett caulk at 7:58 PM on July 11, 2022 [1 favorite]


Preferably by November.
posted by barrett caulk at 8:01 PM on July 11, 2022 [5 favorites]


Hubble vs. JWST, pointed at the same area.
posted by rhizome at 8:11 PM on July 11, 2022 [19 favorites]


Somehow the JWST deep field creeps me out in a way the Hubble deep fields never did. There are just too fucking many galaxies.
posted by wierdo at 8:21 PM on July 11, 2022 [15 favorites]


Wow. Just. Wow.
posted by dg at 8:25 PM on July 11, 2022


Galaxys. Not just a star, a galaxy…

Space is so awesome.
posted by Windopaene at 8:26 PM on July 11, 2022


"Space," [the Hitchhiker's Guide] says, "is big. Really big. You just won't believe how vastly hugely mind-bogglingly big it is. I mean, you may think it's a long way down the road to the chemist, but that's just peanuts to space."
posted by lalochezia at 8:31 PM on July 11, 2022 [25 favorites]


from this Second Helpings of Mercury link:

"The joint European-Japanese BepiColombo mission captured this view of Mercury on 23 June 2023 as the spacecraft flew past the planet for its second of six gravity assist manoeuvres at Mercury."

I'm going to assume this is a typo (based on the timestamp on the actual photo), but I kinda wish something else was afoot!

Thanks for this!
posted by kneecapped at 8:32 PM on July 11, 2022 [1 favorite]


Love this. We can’t spend enough money on this as far as I’m concerned*.

*Seeing as that money would only ever go to more hurty sectors of the military-industrial complex, and not schools or hospitals or anything.
posted by Capt. Renault at 9:02 PM on July 11, 2022 [3 favorites]


Knowing how little of the sky this represents, and seeing hundreds and hundreds of galaxies in just this one pic, and knowing there’s more beyond the limit of what JWST can see… there’s no way there’s not life out there.
posted by azpenguin at 9:06 PM on July 11, 2022 [17 favorites]


Teegeeack AV Club Secretary: if you're talking about the really large spiral there, those bright areas look extended to me. I think they are just knots of star formation, or possibly in some cases satellite galaxies. Spirals can be pretty clumpy (e.g., a nearby example).

Multiple supernovae going off in the same galaxy at the same time is quite unlikely; the Milky Way is about as big as spirals get and best we can tell typically goes 50 years or more between supernovae, and a supernova will only be bright for a couple of months.
posted by janewman at 9:28 PM on July 11, 2022


He Fixed NASA's Giant Space Telescope, Reluctantly [ungated] - "Gregory Robinson was enjoying another job when NASA persuaded him to take on an enormous astronomy project that was billions of dollars over budget and years behind schedule."

The NASA Engineer Who Made the James Webb Space Telescope Work [ungated] - "Greg Robinson turned a $10 billion debacle into a groundbreaking scientific mission. Every moonshot is the result of marginal improvements."

Meet the Woman Who Makes the James Webb Space Telescope Work - "Jane Rigby, Webb's operations project scientist, discusses how NASA plans to wring as much science as possible from the $10-billion observatory."
posted by kliuless at 9:41 PM on July 11, 2022 [12 favorites]


"My God, it's full of galaxies."

The Lights in the Sky are Galaxies

"It's no use, Mr. James -- it's galaxies all the way down!"
posted by away for regrooving at 10:27 PM on July 11, 2022 [3 favorites]


(Why is it oozing gravitational lensing out every pore, though? Is this a statistical cousin of Olbers's Paradox that occurs wherever you zoom this deep, or was this location chosen for lensing?)
posted by away for regrooving at 10:31 PM on July 11, 2022 [1 favorite]


As someone who's spent the better part of the last decade working on the camera, NIRCam, that took the picture...tomorrow's images are going to be even more gorgeous, let me tell you.

I'm exhausted after today, just giddy from looking at the details in this image. We are about the embark on a journey of discovery, and I'm so happy to have this little bit of hope in what has been a really horribly rough time.
posted by RubixsQube at 10:47 PM on July 11, 2022 [150 favorites]


RubixsQube, YOU ABSOLUTE LEGEND
posted by rrrrrrrrrt at 10:52 PM on July 11, 2022 [10 favorites]


our NEIGHBORS
they are so, so beautiful!
posted by rrrrrrrrrt at 10:52 PM on July 11, 2022 [4 favorites]


(Why is it oozing gravitational lensing out every pore, though? Is this a statistical cousin of Olbers's Paradox that occurs wherever you zoom this deep, or was this location chosen for lensing?)

Can't find it now, but I think I saw an astronomer on Twitter say that this region was indeed chosen because there was lots of gravitational lensing.
posted by straight at 10:56 PM on July 11, 2022 [6 favorites]


away for regrooving

In answer to your second question, yes. The area shown was first observed by Hubble by collecting samples over a period of ten days. The bright spot at the center is a galaxy cluster, which is so massive it's kinda pinching at the light traveling past it. This is due to it's immense gravity, which distorts space and time. The galaxies here and their stars are not uniformly distributed, creating the distortions from a perfect circle. One thing you may notice, is a mirror of 'smeared' light on the opposite side of the cluster. This light is likely from the same origin, passing through either side of the galactic lens converging towards us.

I take meals to my elderly neighbour. I always try to stay for a chat because he needs more than food. I showed him this on his imac (I give him wifi too). When I told him every dot is another galaxy, he asked me if there are people there.

Probably. Not like us, but also exactly like us. Maybe they look through telescopes as well. Maybe they make awesome curry for each other too. Probably, yes.
posted by adept256 at 10:58 PM on July 11, 2022 [35 favorites]


This is the first time I've understood what the bright lines ("diffraction spikes" or "diffraction pattern") coming off of individual stars are, thanks to finding this explanation.

They are sort of like seams in the picture, out-of-focus bits of the supports that hold the mirrors getting in the way. The light from stars behind (next to?) them is diffracted making those lines.

Something about the way the diagonal lines line up on the James Webb image makes it much easier for my mind to dismiss them as "window frame" and pay attention to the actual picture behind them. Much better than me always thinking at some level, "Wow, those pretty lines are what stars really look like when you get a good picture of them."

Here's a nice comparison showing Hubble's pictures of the same reason. Quite a dramatic difference! (Astronomy Twitter is some of the best of Twitter.)
posted by straight at 11:16 PM on July 11, 2022 [3 favorites]


Somehow the JWST deep field creeps me out in a way the Hubble deep fields never did. There are just too fucking many galaxies.

This picture has thousands of galaxies within a patch of the sky the size of a grain of sand held at arm's length. Toss a handful of sand into the air; for every grain of sand you can see, there are at least this many galaxies in the sky behind it.
posted by straight at 11:34 PM on July 11, 2022 [13 favorites]


And yeah, that somehow feels much more shocking than when they were comparing Hubble's Deep Field to my thumb.

Here's a gigapan that lets you zoom in on the Hubble Legacy Field image composed of 7,500 photos taken over 16 years. This covers a patch of the sky about the size of the moon. Just imagine what we'll be able to see after Webb has taken a few thousand pictures over several years.
posted by straight at 11:55 PM on July 11, 2022 [4 favorites]


Here's my favorite space video of the week. It's a bit of footage from 2018 but I didn't see it until this week. It's from the Hayabusa 2 probe's encounter with the asteroid 162173 Ryugu.

I've been following landru79 for a while now. Such beautiful images.

Also, I've just learned through the BepiColombo links that there are craters on Mercury named Beckett and Heaney!
posted by vacapinta at 11:59 PM on July 11, 2022 [1 favorite]


The Webb website has a much better diagram explaining diffraction spikes than the article I linked above. Make sure to get a full-res download big enough to read.
posted by straight at 12:05 AM on July 12, 2022 [8 favorites]


Dealing with astronomical numbers with just this minuscule portion of our sky, I think words like "rare" and "unlikely" start to shift into "uncommon" and "maybe" range. We increase and shift that descriptive range with every new photo of each different minuscule area.

Awestruck
posted by filtergik at 1:51 AM on July 12, 2022 [2 favorites]


I laughed when Biden said "America leads the world not by the example of our power, but the power of our example." Just because it's such an American speechwriting trope - not X the Y, but Y the X. Boom, level 100 speechwriting, works with anything, gets em every time. It got me thinking about other inspirational-sounding-but-ultimately-meaningless things that could be said about JWST in the same style...

This telescope will reveal to us not only an infinity of possibilities, but also the possibilities of infinity.

Only once we had thoroughly scoped the launch did we have the certainty to launch the scope.

It's a cosmic light show, a universe of stars, starring our universe.
posted by dashdotdot dash at 1:56 AM on July 12, 2022 [24 favorites]


The Grauniad article on this also has a nice picture with a slider to compare Hubble & Webb side by side. [scroll down]
posted by chavenet at 2:19 AM on July 12, 2022 [1 favorite]


Wait, the same Dr. Becky who makes the JWST cuff links?
posted by inexorably_forward at 3:33 AM on July 12, 2022 [3 favorites]


As an aside, and speaking as an old graphics guy who was schooled during the last great age of the printing press, I am always pleased that NASA always releases pics in TIFF format. That’s all.

That first image is everything I was hoping for! I was definitely surprised by the lensing. Somehow, I wasn’t expecting that, though, thinking about it now, I should have. I wonder, is there any investigation being done to find a way to post-process Webb’s pics and correct for the lensing? And maybe the spikes, too? I get that the lensing itself is a piece of great science data to explore, of course.
posted by Thorzdad at 4:05 AM on July 12, 2022 [5 favorites]


The fact that this photo peers into the very beginnings of the universe and yet there are all these massive galaxies already boggles my mind. I've always thought of star formation as a slow process and galaxy formation as even slower, but at these timescales it's hard to conceive of how it all works. All of human history is not even a breath.
posted by rikschell at 5:08 AM on July 12, 2022 [2 favorites]


I wonder if David Butler's How Far Away Is It? series will get another episode in a few months. (It's a very slow and soothing guide to the unsoothing immensity of the size of the universe, stretched over 20-ish 30 minute episodes.)
posted by clawsoon at 5:08 AM on July 12, 2022 [1 favorite]


They've released a second image! Even better than the first.

(snicker)

Actually, there's a handy countdown clock here.
posted by Insert Clever Name Here at 5:10 AM on July 12, 2022 [1 favorite]


Along with the Hubble / JWST comparison, it should be noted that the Hubble exposure took weeks compared to 12 hours for the Webb.
posted by CheeseDigestsAll at 5:16 AM on July 12, 2022 [1 favorite]


NASA Goddard also recently released a visualization of the Bennu sample impact - I think it was probably more chaotic than anybody possibly expected.

And yeah, rikschell, I get into the same sort of trouble with deep timelines. Like, ok, everything that is solid and rocky is the result of the death of stars having gone through their whole multimillion year lifecycle, man that's a lot of years! But it's a drop in the bucket when your timespan is 14 billion years. And there's a lot of stars going bang to make all the elements and ... right around there is where I just start blinking and pondering cosmology.
posted by Kyol at 5:21 AM on July 12, 2022 [2 favorites]


I've been following landru79 for a while now. Such beautiful images.

Here's a longer, more detailed recap of the Rosetta-Philae mission to 67P/Churyumov–Gerasimenko if you're interested.
posted by Insert Clever Name Here at 5:22 AM on July 12, 2022 [3 favorites]


If you check out that tweet rhizome linked to above, be sure to check out the responses. Some folks created more visualizations of it: animated gifs, closeups, etc.
posted by doctornemo at 5:26 AM on July 12, 2022


I quit Twitter when Musk decided to buy it and the only thing I miss is reading astronomy posts.
posted by rikschell at 5:41 AM on July 12, 2022 [2 favorites]


This slice of the vast universe covers a patch of sky approximately the size of a grain of sand held at arm’s length by someone on the ground.

This is the sort of half horrifying/half wonderful existential sentence that I should think about next time I'm stoned.
posted by Kitteh at 6:13 AM on July 12, 2022 [7 favorites]


To see a World in a Grain of Sand. And a Heaven in a Wild Flower. Hold Infinity in the palm of your hand. And Eternity in an hour.

Some what obligatory Wm. Blake
posted by Insert Clever Name Here at 6:27 AM on July 12, 2022 [13 favorites]


In that case, some more obligatory William Blake:

CRASH: William Blake?
ANNIE: William Blake!
CRASH: William Blake?
ANNIE: William Blake!
CRASH: What do you mean, William Blake?
ANNIE: I mean William Blake!

--Bull Durham
posted by Gelatin at 7:31 AM on July 12, 2022 [1 favorite]


NASA live video presentation just started:
https://www.youtube.com/watch?v=nmMRMIE3MGw
posted by doctornemo at 7:32 AM on July 12, 2022


If the timestamp below this comment is close to NOW, please STOP reading and move over to NASA TV
posted by DreamerFi at 7:38 AM on July 12, 2022 [1 favorite]


Big Government overreach!
posted by kirkaracha at 7:43 AM on July 12, 2022 [1 favorite]


Thanks DreamerFi, I was trying to watch the stream on YouTube and it was a laggy mess. NASA TV seems much smoother.
posted by Monster_Zero at 7:48 AM on July 12, 2022


We can gather Exoplanet spectrums from lightyears away, but cutting to the Canadian team without it being a mess….science can only dream.

(This is great! Oh star death up next!)
posted by inflatablekiwi at 7:52 AM on July 12, 2022 [1 favorite]


She said "scientific nerve centre", but it sounded a lot like "scientific nerd centre."
posted by clawsoon at 7:53 AM on July 12, 2022 [3 favorites]


Those two phrases are equivalent anyway..
posted by DreamerFi at 7:56 AM on July 12, 2022


“I’m not dying, tis but a scratch” - planetary nebula
posted by inflatablekiwi at 7:58 AM on July 12, 2022


Since they never got around to renaming the thing allow me to introduce the new name for the JWST: the Just Wonderful Space Telescope. (First usage).
posted by Nelson at 8:01 AM on July 12, 2022 [10 favorites]


It’s cool to see all the kids at the watch parties. Hope they have more of that - even 5 seconds on the screen will be something those kids will never forget.
posted by inflatablekiwi at 8:07 AM on July 12, 2022


The waves in the Southern Ring Nebula image are just jaw dropping. Image here, find the full res link on this page.
posted by azpenguin at 8:11 AM on July 12, 2022


I imagine a lot of relieved people are happy enough it is the Just Works Space Telescope given the $10 billion cost.

Also Stephan’s Quintet decent band name/username etc. Cool image.
posted by inflatablekiwi at 8:12 AM on July 12, 2022


>Hubble vs. JWST, pointed at the same area.

I can't find a citation now but I read somewhere that Hubble took two weeks to capture that image and JWST captured its much more detailed version in 2 hours. EDIT: Or, what CheeseDigestsAll already said.
posted by scottatdrake at 8:15 AM on July 12, 2022 [2 favorites]


Star birth! Congrats to the Universe - they are beautiful!
posted by inflatablekiwi at 8:21 AM on July 12, 2022 [2 favorites]


For all of your desktop wallpaper needs, all of the images including full res versions are on ESA's Webb site. (Website. Harhar)
posted by azpenguin at 8:27 AM on July 12, 2022 [5 favorites]


I wonder, is there any investigation being done to find a way to post-process Webb’s pics and correct for the lensing? And maybe the spikes, too?

One thing I'm not clear about and would like to Ask An Astronomer is whether the diffraction spikes are only where a star just happens to line up with the inherent seams in the telescopes mirrors or whether they are what this telescope sees any time it tries to look past a star at the distant galaxies behind it.

If it's the former, you'd think they could easily correct the spikes by moving the camera a bit, but if it's the latter, then anything they'd replace the spikes with would be fictional.

And I don't understand gravitational lensing enough to even speculate about that part.
posted by straight at 8:27 AM on July 12, 2022


On the Comic Cliffs:

“We see examples of structures, that, honestly we don’t even know what they are…….what’s going on here!”
- Dr. Amber Straughn with words that will inspire decades of research.
posted by inflatablekiwi at 8:34 AM on July 12, 2022 [1 favorite]


Star birth! Congrats to the Universe - they are beautiful!

And in no time they become hot young stars.
posted by clawsoon at 8:35 AM on July 12, 2022 [2 favorites]


I noticed a figure eight in the upper left quadrant, and I wondered if that isn't also a reflection, as there were large stars in similar places on both halves. I think it amazing to see the infinity symbol on a picture of infinity.
posted by Oyéah at 8:38 AM on July 12, 2022


Webbsite!
For a fine Webb sight.
posted by doctornemo at 8:41 AM on July 12, 2022


Southern Ring Nebula, private pool, members only!
posted by Oyéah at 8:41 AM on July 12, 2022 [1 favorite]


I had to blow the dust off an old bottle for this occasion and join the party. Please raise your glass for the triumphant scientists. Can you imagine, your life's work sitting on top of 1000 tonnes of rocket fuel, about to go boom? It worked! Congratulations!

We can tell it's a cloudy day on a distant planet. We didn't even have evidence there were planets around other stars when I was in high-school, and I'm not that old.

I was impatient to chat about this so I mentioned in the free thread that I hoped to see a smiley face, and I got it. If you look at the quintuple galaxy image, two of the galaxies form the eyes. It's the biggest fucking smiley face in the universe. All the smiling scientists, the universe smiles back.

They've really earned this. Their work is complete, and now it begins in earnest. Cheers!
posted by adept256 at 8:45 AM on July 12, 2022 [13 favorites]


One thing I'm not clear about and would like to Ask An Astronomer is whether the diffraction spikes are only where a star just happens to line up with the inherent seams in the telescopes mirrors or whether they are what this telescope sees any time it tries to look past a star at the distant galaxies behind it.

Every star imaged by JWST will have the six spikes. Light from every object in the field hits all parts of the mirror.
posted by miguelcervantes at 8:48 AM on July 12, 2022 [3 favorites]


One thing I'm not clear about and would like to Ask An Astronomer is whether the diffraction spikes are only where a star just happens to line up with the inherent seams in the telescopes mirrors or whether they are what this telescope sees any time it tries to look past a star at the distant galaxies behind it.

They are not. The spikes are caused by the seams and the struts, but not in the way that a window frame obscures part of the picture. They put a 'hard edge' in the light and light waves like to bend around hard edges.

The spikes are actually happening to every point of light in the picture. But for extended objects, all the spikes from each point overlap and produce a weak background that you can't see in the image. And same for isolated, less bright, points. It's only isolated points (single stars) that are particularly bright, where the impact of the spikes is not blurred out and is strong enough to see over the general background.
posted by BlueDuke at 8:50 AM on July 12, 2022 [7 favorites]


Imagine what the next one they send up will show! It'll blow your mind!
posted by Czjewel at 8:55 AM on July 12, 2022 [1 favorite]


The next one? OK.

Do you remember the Arecibo telescope? The one from the James Bond film. They took advantage of the dish shaped geography to embiggen it. Why not do that on one of those dishy craters on the moon? It doesn't even have to be solid, we could roll out a mesh made compact for transport. As long as the mesh is finer than the wavelengths we observe, we're in business.

We've made liquid mirrors on Earth, we know they work. You take a big pool of shiny fluid and swirl it until it's the desired shape. You know how you blow bubbles by dipping a ring in soap? We could do the same in space, slowly filling the ring with fluid until it bulges out forming a lens. We could makes this really big, maybe the biggest lens ever. Then you position a distant probe at the focal point to collect the light.

How about LIGO in space? The size of our earthbound LIGOs have natural limitations, we could make them as big as we dare up there. We wouldn't just know if there was a gravitational wave passing by, we'd get a good idea of it's shape.

Our sun is massive enough to be a gravitational lens.

Dream big, we can do this!
posted by adept256 at 9:15 AM on July 12, 2022 [3 favorites]


I wonder how many things in those photos still exist. If we're looking back in time 13 billion years, individual stars would certainly have burned out, but what's the lifespan of a galaxy? Will supernova generate enough material to generate new stars keeping the galaxy "alive" or do they slowly fade and get gobbled up by black holes?
posted by CheeseDigestsAll at 9:30 AM on July 12, 2022 [1 favorite]


So, how much longer before we can retire Olber’s Paradox? It does seem like the deeper we look, the more ‘the void’ seems to actually be full of ‘stuff’.
posted by Insert Clever Name Here at 9:31 AM on July 12, 2022


'The next one' is the Nancy Grace Roman Space Telescope -- basically, a wide-field Hubble that can image much larger areas of sky. It should be launched in the latter half of this decade. It won't deliver sharper or deeper images than Hubble can, though. It will do most of its work at infrared wavelengths, so is like JWST in that respect, but will have blurrier images due to its smaller main mirror. Basically, JWST is good for staring at fewer very faint or small things, NGRST is good for exploring the diversity of objects in our Universe.

After that -- there is a concept for a JWST-type telescope that would work at visible-light wavelengths (as Hubble does), which would give it sharper imaging capabilities than either Hubble or JWST does. It was endorsed in the recent astrophysics decadal survey. However, there's a lot of technology that needs to be developed for it to meet its goal of being able to find biomarkers in the atmospheres of Earth-like planets; the astronomical community is hoping for a launch in the 2040s...
posted by janewman at 9:33 AM on July 12, 2022 [5 favorites]


My astronomy interest has moved mainly to asteroids, so I'm super bummed about the delay in the launch of Psyche (link at top of page). Psyche has a metallic surface (per spectroscopy) yet it's only about half as dense* as iron/nickel meteorites. Mysteries abound!

*We know its mass from its gravitational effects on other asteroids (Psyche is big). We know its size from stellar occultations.
posted by neuron at 9:33 AM on July 12, 2022


CheeseDigestsAll: some of those galaxies will still be forming stars today thanks to gas that has flowed into them over time (supernovae tend to suppress star formation rather than enhance it). Others have had their star formation totally suppressed, in part due to being so massive that the gas around them is moving fast and stays hot (only cold gas can form stars), with radiation from hot material around their central black holes playing a secondary role.

Galaxies that aren't forming stars will still be there, though. The lowest-mass stars use their fuel slowly and can sustain fusion for a trillion years, give or take. Even after that they will leave white dwarves behind. They don't get sucked into a central black hole; unless you're super-close to it, the gravity of a black hole works just like Newton's gravity, and things stay in stable orbits (and the central black holes have only a minor gravitational effect in general within a galaxy; stars dominate the mass and hence the gravitational field unless you're really close to the center).
posted by janewman at 9:38 AM on July 12, 2022 [5 favorites]


Insert Clever Name Here: You'll notice lots of blank space in these images, even though we can spot galaxies almost all the way back to the Big Bang with JWST. That's the ultimate resolution to Olber's paradox: if something is far enough away that light would have to travel >13.8 billion light-years to reach us, we can't see it, so the total number of galaxies along your line of sight is limited.
posted by janewman at 9:42 AM on July 12, 2022 [1 favorite]


So, how much longer before we can retire Olber’s Paradox? It does seem like the deeper we look, the more ‘the void’ seems to actually be full of ‘stuff’.

Isn't it possible that the universe is infinite and full of infinite stuff but expansion means that only a finite amount of light from all that stuff makes it to us?
posted by clawsoon at 9:44 AM on July 12, 2022


janewman: ah, yes, I can see that. At some point we’re looking at the very edge of what can be observed by dint of how old we believe the universe to be.
posted by Insert Clever Name Here at 9:56 AM on July 12, 2022 [2 favorites]


clawsoon: yes, that is exactly the resolution to Olber's paradox. We have strong evidence that the Universe is much larger than the visible part of the Universe, and possibly infinite, but there is a limit to how far away light can reach us from.
posted by janewman at 10:09 AM on July 12, 2022 [3 favorites]


At some point I learned that at least one version of the Big Bang equations assume that the universe is and has always been infinitely large, which put a whole different spin on the Big Bang for me.
posted by clawsoon at 10:14 AM on July 12, 2022


How about LIGO in space?

LISA.
posted by solotoro at 10:44 AM on July 12, 2022 [1 favorite]


I got up early to watch John Glenn be the first man in space.(Yes, I know this is incorrect, but I'm describing me hunched on the front room clutching my bowl of Cherrios.) That our universe has come to this, in my lifetime, is astounding.
posted by SPrintF at 10:53 AM on July 12, 2022 [4 favorites]


How about LIGO in space?

Meet LISA.

EDIT: psych
posted by sjswitzer at 11:22 AM on July 12, 2022 [1 favorite]


How can something infinite expand? Expansion requires an edge. If it has an edge it has a limit, and if it has a limit it is not infinite. Immeasurably big, perhaps. Or have the definitions changed on me again (happens periodically when you get to be my age)?
posted by It's Raining Florence Henderson at 11:45 AM on July 12, 2022


How can something infinite expand?

I think of the number line. What happens to it if you multiply every number by 2? It "expands". Yet its overall "size" did not change -- it was infinite, and remains infinite. Apply that reasoning to an infinite 3-D space, where every distance is being scaled up.
posted by phliar at 11:51 AM on July 12, 2022 [9 favorites]


It's Raining Florence Henderson: Expansion doesn't require an edge. Think about the surface of a balloon (ignoring the hole where you inflate it): as the balloon gets bigger, the surface gets bigger, but you can travel continuously across that surface without running into an edge.

Basically, the equations of general relativity allow space itself to expand or contract; the distance between any two specific points in the universe will grow with time as space expands (unless they are close enough together that gravity pulls them towards each other). Basically, we use a coordinate system that expands with the Universe when we do calculations in cosmology ('comoving' coordinates), and rescale everything according to the Universe's growth.

In fact, relativity requires space -- even in an infinite universe -- to either be expanding or contracting; staying the same size turns out to be unstable (Einstein put his 'cosmological constant' into GR to try to prevent this behavior, but the equations turn out to still be unstable with it included).
posted by janewman at 11:53 AM on July 12, 2022 [4 favorites]


Here's a whole bunch of Webb images alongside their corresponding Hubble image, with bonus slider!

Webb Compare
posted by tommasz at 12:00 PM on July 12, 2022 [10 favorites]


tommasz... broken link?
posted by clawsoon at 12:02 PM on July 12, 2022


tommasz... broken link?

Link fixed
posted by tommasz at 12:05 PM on July 12, 2022 [1 favorite]


janewman: Here's a cosmology question you (or maybe someone else here) might be able to answer, though it's a bit off-topic for JWST:

So when we look out in any direction from our point in the observable universe, the oldest light we could hope to detect is (approximately) 13.7 billion years old, which is to say the furthest objects we can detect are (approximately) 13.7 billion light years distant. Now imagine I observe one object at this distance, lets call it O(a), and then another object, lets call this O(b), that's located 180 degrees away from O(a), i.e. at the other end of the observable universe. The logical distance between O(a) and O(b) would be 27.4 billion light years. But that doesn't make any sense since the universe isn't old enough for two objects to be that far apart (causally separated) from each other. Do you know how this gets reconciled in modern cosmology?

Any light you or anyone else can shed on this would be appreciated.
posted by Insert Clever Name Here at 12:23 PM on July 12, 2022


I'm no expert, but Insert Clever Name Here... does the fact that the universe might have always been infinitely large - both before and after expansion - in Big Bang cosmology help wrap your head around it at all?
posted by clawsoon at 12:30 PM on July 12, 2022


No, the objects were closer than that because, as you point out, the Universe was smaller then.

As you look farther away, in any direction the Universe is smaller the farther you look. One way of thinking about this is that the older Universe are 'stretched out' to cover the space. In actuality of course it is an illusion and it is Light that is being stretched.

In fact this stretching means that beyond a certain distance, the farther away the galaxy is the BIGGER it appears in the sky!! Again because a smaller Universe (the past Universe) is being visually stretched.
posted by vacapinta at 12:33 PM on July 12, 2022 [3 favorites]


Insert Clever Name Here; you may want to dip into the cool cool waters of PBS’s Space Time hosted on YouTube. I am having a hard time finding a link of the exact episode, but I do believe they’ve covered just this very question (or something close enough to provide you a migraine and an answer).
posted by furnace.heart at 12:47 PM on July 12, 2022


Wow. OK. I can kind of wrap my brain around that: the observable universe is expanding, so O(a) and O(b) were closer together (and smaller) when the light I'm now seeing from them was emitted, (approximately) 13.7 billion years ago. Which makes me now wonder: so can we know how close they were back then? Is the rate of expansion of the universe considered to be even and constant or...?)

Excuse me. I gotta have a drink.

(And thanks to everyone who helped change my mind today. ;->)
posted by Insert Clever Name Here at 12:52 PM on July 12, 2022


My wife had to cut off an 11 year old at YMCA day camp today who wanted to argue that the Big Bang didn't happen as she was showing the photos to the kids. The theme this week is Space Camp.
posted by COD at 12:56 PM on July 12, 2022


When trying to understand anything on the scale of the Universe this ask me has one of the better suggestions.

To get a really visceral sense of this, I recommend eating psilocybin mushrooms while lying on your back in the sand on a clear night in an Australian desert.
posted by inflatablekiwi at 1:14 PM on July 12, 2022 [2 favorites]


Being on a boat in the middle of lake Titicaca during a new moon also provides a pretty dope light show to get some sense of the vastness of the cosmos. Very few things have brought this atheist close to what could be called a ‘religious experience’ but that’s one of them. You can read a book by the light of the Milky Way that far up in elevation with no light pollution or clouds.

I’ve been to ‘dark zones’ of North America, and I agree that the Southern Hemisphere really takes the cake for an impression of the vastness.
posted by furnace.heart at 1:27 PM on July 12, 2022 [3 favorites]


...you may want to dip into the cool cool waters of PBS’s Space Time hosted on YouTube.

OK, those were pretty intense, at least the two or three I just watched.

"The boundary of a conformally-compactified anti-de sitter space is itself a conformally-compactified minkowski space with one fewer dimensions."

Gonna steep myself in a few more of these and see if I can then convince myself that I'm barely able to understand any of it. ;->
posted by Insert Clever Name Here at 2:18 PM on July 12, 2022 [1 favorite]


How Far Away Is It - 16 - The Cosmos might be slightly easier to wrap your head around.
posted by clawsoon at 2:32 PM on July 12, 2022 [1 favorite]


My wife had to cut off an 11 year old at YMCA day camp today who wanted to argue that the Big Bang didn't happen as she was showing the photos to the kids. The theme this week is Space Camp.

There is an interesting argument to be had on that point, but it hinges on what you mean when you say "The Big Bang". It's as certain as we can be that the universe was once very small and very hot. The CMB and its fluctuations are proof of this. Within the first tiny bit (the initial inflationary period in which the universe expanded from the size of a proton to the macro scale) the science is not so certain.

Inflation is probably right, but there's not nearly so much evidence as there is for the later stages of the early universe before recombination. TBH, I find it a bit gobsmacking that people can even figure out ways to prove what the universe was like back when the universe was still opaque, but they did.
posted by wierdo at 2:40 PM on July 12, 2022 [4 favorites]


the universe was once very small

Very small, or very dense? The whole universe, or the visible universe?
posted by clawsoon at 2:47 PM on July 12, 2022


clawsoon: Thanks, that was also helpful, even if it took a while to get there. Still plenty of maths but less head hurting. ;->
posted by Insert Clever Name Here at 3:23 PM on July 12, 2022 [1 favorite]


My wife had to cut off an 11 year old at YMCA day camp today who wanted to argue that the Big Bang didn't happen as she was showing the photos to the kids. The theme this week is Space Camp.

There is an interesting argument to be had on that point, but it hinges on what you mean when you say "The Big Bang".


Yep, as I understand it there is still some uncertainty about this, particularly about the definition of the Big Bang itself and what that actually means.

It's been a long time since I even really tried stretching my brain around this kind of cosmology and astrophysics but I could easily be that kid that doesn't necessarily believe in the Big Bang as it is currently and commonly understood and defined but being unable to articulate it in a way that wasn't misinterpreted as something else.

Especially since we have some very serious limitations and issues being able to see past our light sphere and the CMB with observation alone.

In any case the Big Bang and how it relates to General and Special Relativity has always kind of stuck in my craw and my intuition is that we're still not quite there yet, and that the Big Bang is an artifact of trying to reconcile General/Special Relativity with what our limitations of our observation.

As I understand it and recall Hawking gets into some of this uncertainty about the Big Bang and an expanding universe in a Brief History of Time and as I recall he has suggested similar things that what we know or take for granted about the Big Bang and CMB may be wrong.

My intuition is that the truth is even larger and stranger than we currently think it is.

I can't remember the name of the physicist or theory but there's apparently some precedent that not only are our observations limited by our light sphere and observable universe and the CMB but that our observable universe is also some tiny local fraction of the total universe and that what we can see and know is just this small bubble of the whole, and there isn't really any known or theoretically possible way to see or observe beyond these limitations that doesn't break relativity and most of what we know about astrophysics and cosmology.

IE, what we can observe in our observable universe may be expanding and may have come from a very hot, dense expanding source - but that doesn't mean everything else in the universe is, too.

It may be more accurate to think of our observable universe as just part of one bubble in a whole sea of foam that exists on scales and timeframes so large that it vastly exceeds everything we think we know about the universe.

This line of thinking gets very weird in a hurry and takes deep dives into really heady stuff like trying to define how many dimensions there really are, what time and space really are and off into the weeds of string theory and more.

There's also the thorny issues with dark matter and dark energy that we've been working with to help justify the theories of a singular Big Bang in a constantly expanding universe and reconciling that with, well, everything we think we know today.

In any case it's always made more sense to me to think about the universe as something varied, cyclic and, well, "foamy" that has it's own fractal-like hyper/giga structures that mirror what we're seeing with intergalactic filaments and varied densities, but on scales so large they would take multiple observable universes to even start to see or understand those structures, as well as even be able to correlate those observations across distances so incredibly vast they totally break the information transmission parts of relativity in ways that might make even Hawking or Einstein question their sanity.

All of this weird, vague hand waving aside it also just makes sense to me that Einstein and Hawking end up being "mostly right" in the same way Newton was "mostly right" about macro scale physics at a given useful scale but could only be so right, given the state of the art of our math, physics and astronomical observations.

I would not be at all surprised or alarmed to learn that the universe is even weirder and stranger than we can even begin to imagine or model even if our science and knowledge progressed to nigh-impossible galactic or intergalactic scales.

Even weirder and more hand-wavy? I also would not be at all surprised (alarmed, sure) if we discovered we were in a simulated or holographic universe and artifacts like the CMB and even general/special relativity itself are the artifacts of the finite resolution, scale or time and space of that simulated universe.

The universe isn't just vastly, hugely, mind-bogglingly big, it's also likely so improbably weird we can't really and truly wrap our heads around it even if we lucked out and made it through the Great Filter to exist at larger than galactic scales and time frames.

Anyway, now I need to go touch grass and stop staring into the void before I get a raging headache and a nose bleed. Keep banging those rocks together, guys!
posted by loquacious at 3:38 PM on July 12, 2022 [5 favorites]


Which makes me now wonder: so can we know how close they were back then?

To answer my own question: Yes, we can determine both the distance the object was from us when the light we're measuring at the current moment was emitted by it, as well a how much further the object appears to have moved away from us since then, due to the expansion of space.
posted by Insert Clever Name Here at 3:42 PM on July 12, 2022 [1 favorite]


Very small, or very dense? The whole universe, or the visible universe?

We can only be absolutely certain about the observable universe, of course, but that was both very small and very dense.

Beyond that, sure, eternal inflation in a single topological universe is a possibility, as are all kinds of other theories, but none of them are supported by hard evidence. All we can say for certain is that the universe we inhabit (and could in principle visit or at least observe given some sort of FTL travel) is somewhat larger than the part of the universe that is observable from Earth.
posted by wierdo at 4:09 PM on July 12, 2022 [1 favorite]


Looking at Stephan's quintet, it might be, the spiral galaxy on the left is what is left when the lower and upper galaxies joined, started pushing out clouds of extra stuff, in the middle and moved to the left. We might be missing something about how the passage of time looks at great distance, and a lot of the extra stuff is just views of what is there, as a dynamic system whose parts we can't unsee because of how time works.
posted by Oyéah at 4:20 PM on July 12, 2022 [1 favorite]


our observable universe is also some tiny local fraction of the total universe and that what we can see and know is just this small bubble of the whole

Sean Carroll just did a podcast on the different types of multiverse (the quote describes one of at least three possibilities).
posted by CheeseDigestsAll at 5:20 PM on July 12, 2022


The "grain of sand at arm's length" is evocative but what percentage of a typical night sky is that?
posted by Rumple at 5:23 PM on July 12, 2022


Apologies for the massive derail, but it seems at least tangentially related (literally).

phliar and janewman, thank you both very much for responding. I appreciate it immensely, so please don't take this reply as pushback. What I'm writing here now is just me documenting my thought process as my limited brain tries very hard to understand. I had actually considered exactly those two points right away, but then ran into the following arguments with myself.

phliar: I think of the number line. What happens to it if you multiply every number by 2? It "expands". Yet its overall "size" did not change -- it was infinite, and remains infinite. Apply that reasoning to an infinite 3-D space, where every distance is being scaled up.

IRFH Arguing with Self: But a number line is a theoretical construct with no physical properties, so we can choose to perform all kinds of operations on it that don't have to conform to physical reality. But once we assign those numbers to represent actual real elements of physical reality, we run into limits. Now we can't say that the number line is infinite unless we set that as an initial condition of what it measures, which means we can no longer use that number line to prove anything about infinity. You can't use an initial condition to prove itself.

And how can physical reality scale up if there is no more up to scale to? If the universe is infinite, isn't it already present for all possible up?

janewman: Expansion doesn't require an edge. Think about the surface of a balloon (ignoring the hole where you inflate it): as the balloon gets bigger, the surface gets bigger, but you can travel continuously across that surface without running into an edge.

IRFH Arguing with Self: Pretty sure I used the term "edge" incorrectly for the kind of maths required. Maybe "boundary" is a better term for what I mean? But that might be the wrong term, too. At any rate, if you travel continuously around the surface of the balloon, you won't run into an edge. But if you add any reference point at all and travel around the surface of the balloon, you will eventually wind up right back where you started. Not an analogy for infinity that my brain finds persuasive. (And yes, you could theoretically inflate the balloon faster than I could travel around it back to my reference point, but that doesn't really make the surface an infinite circumference.)

And its surface area can only expand if its volume increases, which means its boundary is moving through space (and therefore occupying more space), which it can only do because it is not already occupying all possible surrounding space. If the universe is infinity-minus-1 volume big, I can buy the argument that it can still expand. But if it is truly infinite, then there is no more there to move to. It could move from more dense to less dense within those limits, but not infinitely.

IRFH Taking the Counter Argument with Self: I see where you're going with this. If the universe were only infinite in the sense that all possible space-time eventually wraps back around itself, then expansion couldn't be a universal property, because expansion in one part of the system would eventually create compression in others, and eventually balance. So infinite expansion requires an infinite universe. But if the universe is already infinite, then how can it expand? Wherever it would expand to, it's already there.

But is it already there?

I mean, how are we defining our terms? What do I mean by "universe" in this discussion? Do I mean the space-time continuum, do I mean space occupied by something, by anything at all, at any size? I think that's how I've been thinking of it. I've been thinking of the universe in terms of what it contains, of matter and energy. But what if the universe is more than that? In fact, what if the universe is infinitely more than that? What if the universe is infinite but the occupied universe is finite but expanding? In fact, what if the universe isn't infinite, but just potentially infinite? What if the universe is infinitely expanding and the stuff in it is infinitely expanding? Is that any different than being infinite?

I don't know know any more. I just know that working through that "out loud" just broke down my own barriers to conceptualizing an infinitely expanding universe. So I'm dropping this here as a monument to my own density.
posted by It's Raining Florence Henderson at 5:25 PM on July 12, 2022 [2 favorites]


To answer my own question: Yes, we can determine both the distance the object was from us when the light we're measuring at the current moment was emitted by it, as well a how much further the object appears to have moved away from us since then, due to the expansion of space.

See also: Observable Universe - Size.

Or if you really want to bend your brain into a soggy half chewed pretzel, there's this gem from the introductory overview of that wiki:
If the universe is finite but unbounded, it is also possible that the universe is smaller than the observable universe. In this case, what we take to be very distant galaxies may actually be duplicate images of nearby galaxies, formed by light that has circumnavigated the universe. It is difficult to test this hypothesis experimentally because different images of a galaxy would show different eras in its history, and consequently might appear quite different. Bielewicz et al.[27] claim to establish a lower bound of 27.9 gigaparsecs (91 billion light-years) on the diameter of the last scattering surface (since this is only a lower bound, since the whole universe is possibly much larger, even infinite). This value is based on matching-circle analysis of the WMAP 7 year data. This approach has been disputed.[28]
Among many things this means there's a non-zero chance that we can observe our own galaxy in own our sky at a perceived distance billions and billions of light years away the past because the photons from it got so fucking bent they came back to us*.

Which is why part of my vague, amateurish intuitions about questioning the Big Bang as-is currently accepted is that a lot of this is based on (very well informed) assumptions. Some of them as basic as the constant of the speed of light itself in vacuum, again from the subsection about size, last paragraph:
The light-travel distance to the edge of the observable universe is the age of the Universe times the speed of light, 13.8 billion light years. This is the distance that a photon emitted shortly after the Big Bang, such as one from the cosmic microwave background, has travelled to reach observers on Earth. Because spacetime is curved, corresponding to the expansion of space, this distance does not correspond to the true distance at any moment in time.[37]
Which gets super weird when trying to think about that in terms and reconciling that the speed of light is, indeed variable (with a theoretical maximum) with the idea that space isn't a complete vacuum at all, that it's not just curved but totally warped or even before you start adding in theories about dark matter or how this all works out with non-Euclidean spacetime or even more dimensions - or what time even really is!

Meaning if at some point we discover that if the maximum speed of light isn't actually as much of an absolute as we thought it was (how you doing over there, tachyons?) then a lot of these theories about size or age of the observable universe would be different, wrong or "mostly right" - and that's just one factor and observation informing these (again, very well formed) theories about all of this.

There's still major questions left to answer. Like the speed of gravity or what it even really is and what kind of force it is and where it fits in. Or if the maximum speed of light changes in the presence of extreme gravity. Or if that can be reconciled with relativity. Or how to map any of this across non-Euclidean spacetime.

Right now we can can barely even quantify or define what time itself even is or how constant it is even within the framework of relativity outside of local observations of physical evidence, say counting the vibrations of an atom and using that as our local yardstick that's entirely based on observations of our local spacetime comparing the speed of light to, say, vibrating cesium atoms.

I'm getting way out of my depth here but how do you even start mapping the physics of gravity, time or the speed of light with extradimensional, non-Euclidean physics? I mean I can wrap partially my mind around the mathematical concepts of dimensions in the sense that "it's the same as 3/4 dimensions, but with at least one more" and I can kind of handle general and special relativity and a lot of other pieces of this puzzle but oh dear trying to hold both ideas at the same time is a whole different zoo from another planet.

Doesn't the idea of there being more dimensions than, say, four, imply that our local observations of the speed of light and time are different and there's this big, huge question of light or information being able to move through one of those dimensions above four faster than we can quantify and observe from within those four dimensions?

While our scientists, astronomers and physicists and cosmologists are indeed making observations that very strongly support all of this with some very well informed assumptions supported by evidence but I have a whole lot of big questions and a big fat hunch it's still only mostly right and the answers to all of these questions are way, way weirder than we currently think it is.

*Uhm, holy shit! I have an idea. Given all of the above it's not impossible we could view our galaxy from outside itself, if only from the past.

I did go touch grass and smoked some, too, so bear with me here, but I may have just had a huge idea (that probably already exists because I'm not that smart) but if it doesn't exist already and if there's any cosmologists or astronomers out there reading this, please feel free to steal it it.

So we've seen examples of gravitational lensing and obvious examples of distant galaxies being mirrored around warped space time.

Has anyone tried looking for evidence of extreme examples of gravitational lensing, perhaps even looking for a mirror of our own galaxy in the sky that looks like it's an entirely different galaxy?

Or looking for and observationally confirming two galaxies that are actually the same galaxy?

If I was following this idea I'd break it down into two attempted observations, the first idea and more complicated would be attempting to look for and observe our own galaxy from outside through gravitational lensing, the second being trying to observe a single galaxy in two distinct places in our observable sky:

For the first idea if I was going to look evidence of photons of our own galaxy observed as distant and past photons bent back to us I'd look for something unique to uniquely identify it with, perhaps a group of quasars or evidence of black holes that mapped to simulations to roll back time within a certain time frame that matches the observed distance. This is complicated by trying to observe our galaxy from within and then trying to simulate its past.

For the second and maybe less complicated, I would look for observable galaxies that were roughly equidistant but at obtuse angles from each other, with closely matched features or, again, some identifiable hallmark like the presence of a pattern of quasars or black holes or even less esoteric observable optical structures.

If we had a full sky map of the observable universe with the depth of the Hubble deep field or the JWST deep fields along with some generalized map of major gravitational sources and space-time warping with a hearty pinch of time-based simulation, you could do some clever stuff with AI or algorithmic image searches looking for de-convoluted matching galaxies.

A full sky survey and analysis of this scale looking for duplicated observed/apparent galaxies would likely reveal a great deal about many things, including the structure of our local and observable universe and even fundamentals about the speed of light, the speed of gravity and many more questions.
posted by loquacious at 5:26 PM on July 12, 2022 [2 favorites]


We know that light doesn't (in general) "wrap around" like that, at least not on the scale of the observable universe, because we have measured the universe to be flat to within a small margin of error. If it's topologically closed, the radius of curvature is many, many times larger than the observable universe and light would not have had time to travel back to its origin even if the distance to the "edge" was not growing larger faster than light can cover said distance.

We can't place an exact value on the rate of expansion back into the very distant universe, indeed, measurements using different methods are in disagreement. However, the bounds of those measurements can still rule out many possibilities.
posted by wierdo at 5:48 PM on July 12, 2022 [2 favorites]


Also, it should be noted that observations from JWST should help to refine our measurements of the expansion rate, among many, many other things. Which is why it's so freaking awesome and totally worth the money and decades of people's lives that went into building it. We'll get plenty of pretty pictures, but also a lot more hard data that will be useful in astrophysics, cosmology, planetary science, and many other fields.
posted by wierdo at 5:54 PM on July 12, 2022 [1 favorite]


The "grain of sand at arm's length" is evocative but what percentage of a typical night sky is that?

How many grains of sand would it take if you were standing with one on your fingertip outside and floating in space without any plants blocking your view, and you filled in the entire night sky with a shell of sand that blocked all of your view of the sky?

I did some googling and found that estimates range between about 100k grains of sand to a million to cover one square foot one grain of sand deep. This might be wrong, but that's ok, the number is still going to be mind-bogglingly big.

I'm also seeing the size of sand as estimated to be between 0.5 mm and 1 mm, so let's call a grain of sand between 0.5 mm and 1.0 mm, which sounds about right to me.

And let's assume a 2 meter observational sphere at arms length to apply grains of sand. And let us call an "arm's length sphere" as a 2 meter diameter, which gives us a surface area about 50 square meters of sphere. Let's call it 50.

Let's call it 0.5 mm for a grain of sand. That is 100,000,000 million grains of sand to cover 50 m2, or about 0.000001% of the observable sky as a sphere as represented as a grain of sand held at arm's length.

Behind every grain of sand covering that sphere there are billions and billions of stars.
posted by loquacious at 6:01 PM on July 12, 2022


So, if the boundary of the universe exists, and the glowing denizens of our universe, send out light images of themselves then it is possible we are seeing reflections of everything that has happened coming back from the edges. Then a lot of what we are seeing or even confusing with expansion is, these images spreading as they are pulled, and pushed, by other highly charged entities on the bounce back. Point of view is really important and it might be great to take that huge view, again, immediately to see if these phenomena grow. I still think Stephan's might be four views of an occurrence, with the final view of the merger to the left. Anyway the images are evocative, breathtaking, and beautiful. They attest to the worth of us as a species, and we need this at this point in our history. Pictures of the past across space and time. ♡
posted by Oyéah at 6:11 PM on July 12, 2022


People have looked for repeating patterns in the universe (using the cosmic microwave background, the furthest-originating light we can see) and they are not there. As mentioned by wierdo, based upon a variety of measurements we repeatedly find that the curvature of the Universe has to be extremely small, which implies that if it is finite, space has to be only barely curved on average; this implies that it must be very, very large (e.g.: the surface of the Earth is barely curved on average, compared to a human, because its radius is large. The surface of a ball is highly curved, as its small).
posted by janewman at 6:19 PM on July 12, 2022 [5 favorites]


That is 100,000,000 million grains of sand to cover 50 m2, or about 0.000001% of the observable sky as a sphere as represented as a grain of sand held at arm's length.

Less than I thought actually. I think the salient point of view is a human standing on (a flat) earth, so it'd be closer to a hemisphere than a sphere, but that math (divide by 2) I can just about manage on my own. Thanks!
posted by Rumple at 6:23 PM on July 12, 2022


As to seeing two galaxies in opposite directions: indeed, light can't go from one to the other in the age of the Universe (with an asterisk I'll talk about momentarily), as it took 13+ billion years for the light from either of them to get to us (and will take longer to get from us to the other one, as the universe is continually expanded; each of those galaxies are now >40 billion light-years from us, they were closer when light headed our way).

As to the asterisk: in the late 70s/early 80s people asked why the Universe looks similar in opposite directions (e.g., the temperature of the cosmic microwave background is close to uniform), even though light can't get from one place to another (without energy transfer you can't get thermal equilibrium). In the end, it was realized (primarily by Alan Guth) that that problem, as well as a couple of other mysteries (the small curvature of the Universe -- normally if space starts out a little bit curved towards itself, like the surface of a sphere,or away from itself, like at a saddle point, that curvature should get much stronger with time; and the lack of magnetic monopoles) could both be resolved if the Universe grew by a very large factor shortly after the Big Bang. We call this phenomenon 'inflation'.

Basically, the entire observable universe was so tiny before inflation that light could travel anywhere within it in a tiny fraction of a second and bring things to a constant temperature. As a result, points a and b were in causal contact before inflation, even though they have been out of it since.
posted by janewman at 6:28 PM on July 12, 2022 [4 favorites]


There are just too fucking many galaxies.

I feel this. I've been trying reconcile this in my mind along side the stupid crap in my work email inbox and all the mundane details of daily life.
posted by paper chromatographologist at 6:31 PM on July 12, 2022 [1 favorite]


If you very desperately need to know what religious people think about the James Webb, the Vatican Observatory is PUMPED. The Vatican Observatory was founded in 1582 (one of the oldest research institutions in the world!) and has always been staffed with scientists, and always challenging the "religious" understanding of the universe. They are all super-amped (because they are all astronomers).
posted by Eyebrows McGee at 6:32 PM on July 12, 2022 [3 favorites]


The problem of the negligible observed curvature of the Universe is solved by inflation via the expansion itself: if you take a curved ball and expand it to the size of the Earth, the local curvature becomes a whole lot less. Inflation expands things by a much bigger factor than that (>10^25).
posted by janewman at 6:33 PM on July 12, 2022 [2 favorites]


I am late to this party but have a question. I can see the resolution of the Webb pictures compared with the Hubble, and there is a difference. But as a layman, I don't know if I can grasp the significance of that difference. It's like going from 480p to 4K, right? But what I want to know is what the NASA scientists are floored by. What is it they are learning from these images? What are the things they are learning that we--as in, the top level scientists in the know--didn't know earlier this year?

In short, aside from the great photos, what are we observing that is new?
posted by zardoz at 8:32 PM on July 12, 2022 [1 favorite]


What's new isn't actually the sharpness of the images, but rather the faintness of what can be observed and, especially, the types of light that can be collected.

Basically, the blurriness of the images you obtain from a space telescope is directly proportional to the the wavelength of light you are observing, but inversely proportional to the diameter of the telescope. JWST's mirror is ~2.5x larger than Hubble's, but the shortest wavelengths where JWST is sensitive is about ~2.5x larger than the shortest wavelengths where Hubble is sensitive, so basically the two factors cancel out (the longer-wavelength MIRI images from JWST are noticeably blurrier than the shorter-wavelength ones). Of course, the long wavelength end of what Hubble can do overlaps with the shortest wavelengths from JWST, and JWST does deliver sharper images in that case.

So where does JWST gain? First of all, that ~2.5x larger mirror collects ~7x as much light per second from everything you are observing as Hubble's does, so you can detect fainter details. However, the bigger difference is in the wavelengths they work at. Hubble mostly works at visible-light wavelengths -- the sort of light our eyes can see -- though it can push a little into the ultraviolet and a little into the infrared. Visible light is great for observing sun-like stars in the present day, but it's easy to block it with interstellar dust, and it's poor for looking at colder parts of the universe or distant parts of the universe where light has been stretched out a lot (redshifted) by the time it gets to us. So JWST can observe stars being born within their dusty nurseries, study the atmospheres of extrasolar planets (which are cooler than stars and host molecules that interact with infrared light), and observe the most distant galaxies whose starlight has all been redshifted into the infrared part of the spectrum.

Because of JWST's IR focus and lack of visible-light capabilities, though, there are plenty of things that Hubble can do that JWST can't, just as much as the reverse is true...
posted by janewman at 9:33 PM on July 12, 2022 [7 favorites]


If all these galaxies makes you feel insignificant, consider this.

If there was another planet out there somewhere that had intelligent life on it, how significant would that be to you? How much more interested would you be in that planet than a picture of a thousand galaxies? How many uninhabited star systems would you sacrifice to save that planet from destruction?

Even if every galaxy has thousands of inhabited planets, we are still in the top .00001% (by mass or volume) of the most interesting things in the universe.

Planets are cool. Planets with life are amazing.
posted by straight at 11:56 PM on July 12, 2022 [1 favorite]


All we can say for certain is that the universe we inhabit (and could in principle visit or at least observe given some sort of FTL travel) is somewhat larger than the part of the universe that is observable from Earth.

Is it also fair to say that so far we've found no indication of a central point, other than the fact that we're in the centre of all the light that's been able to get here in the past 13 billion years? That there's no gravitational or microwave or mass density or whatever signal in the data saying "everything is moving away from this point" or "the edges of the universe are all equidistant from that point"? No indication of any kind of edge or centre at all so far?
posted by clawsoon at 3:02 AM on July 13, 2022


Webb Compare

The improvement in the depth and texture of the Southern Ring Nebula is spectacular.

I could've sworn that I read that the picture of all the galaxies was from an area the size of a grain of rice held at arms length, but, no, it is indeed a grain of sand.
posted by clawsoon at 3:08 AM on July 13, 2022


About the "how much of the sky is that grain of sand" question: I found a more precise measurement of "about 2.4 arcmin across" here. So if I'm doing my math correctly (and someone please correct me if I'm not):

(2.4/60)2 = 0.0016 degrees squared for the area of the image
4π * (180/π)2 = 41252.96 square degrees in the full sky, so 20626.48 square degrees in the half-ish you can see on any given night.
20626.48/0.0016 = 12,891,550

So that picture covers about a thirteen millionth of the sky that you can see.
posted by clawsoon at 3:33 AM on July 13, 2022 [2 favorites]


...and a twenty six millionth of the full sky, for clarity.
posted by clawsoon at 3:41 AM on July 13, 2022 [1 favorite]


Time for some more Blake, perhaps?

When the sun rises, do you not see a round disc of fire somewhat like a guinea? O no, no, I see an innumerable company of the heavenly host crying Holy, Holy, Holy is the Lord God Almighty.

From 'A Vision of the Last Judgement' (1810) in 'MS Note-Book' p. 95
posted by Insert Clever Name Here at 3:58 AM on July 13, 2022


“...which it can only do because it is not already occupying all possible surrounding space.”

Your intuition of "space" and "universe" is misleading you. "Expansion" doesn't require "expansion into", for example.

The language of physics is mathematics, and the mathematical abstractions that apply here — such as manifolds — are often themselves counter-intuitive even as abstractions. When we use them to model what we observe and those models work, the physical implications of that are arguably even more counter-intuitive. So it's extremely tricky and often very misleading to reason these things out in ordinary language.
posted by Ivan Fyodorovich at 7:26 AM on July 13, 2022 [4 favorites]


clawsoon: people have done tests for whether the universe is homogeneous (similar in average density everywhere) and isotropic (similar in every direction) and the Universe does pass those tests. The statement that the Universe is homogeneous and isotropic turns out to be equivalent to the statement that the Universe has no center and no edges (these are both statements of the cosmological principle, a generalization of the Copernican principle that we should not expect to be in a special place within the Universe).

That said, the strongest arguments against there being a center or edge are probably philosophical (cosmology was mostly a field of philosophy, not physics, till the 1970s). As was pointed out a couple of thousand years ago, if there were an edge to the Universe you could go up to it holding something and stick it out further, so that edge couldn't be real (wikipedia calls that the 'javelin argument', though I've never heard that name before). Similarly, if the Universe has a center than someone can be at a special place in the Universe, and the cosmological principle breaks down.

As a result, our mathematical models of the Universe all start by assuming homogeneity and isotropy, and those models are incredibly successful (matching high-precision observations of the CMB with exquisite accuracy).
posted by janewman at 8:02 AM on July 13, 2022 [4 favorites]


Resurrecting the discussion of diffraction spikes (the spikes around stars in the Webb images) earlier: one of my students sent along this nice infographic from the Space Telescope Science Institute: here.
posted by janewman at 8:07 AM on July 13, 2022 [1 favorite]


As mentioned above, there is an absurd, possibly terrifying number of galaxies out there.

I've complained about this recently on FanFare, so it's obviously a bugbear of mine lately, but a lot of science fiction, especially film/tv, equate our galaxy with the whole universe. Some writers clearly think the two are the same. This is such a failure of imagination — an example of colossal anthropocentric hubris.

There are about 100 billion stars in our galaxy, the Milky Way. It's about 4 light years from here to the nearest star and the Milky Way is about 100,000 light years across its disk.

The nearest (non-dwarf) galaxy, Andromeda, is 2.5 million light years away.

If — and that's a huge "if" — humans are ever able to travel to another star, maybe even hundreds of light years away, we will never, ever travel to another galaxy and that's almost certainly equally true about someone from another galaxy visiting ours. Science fiction leads us to want to believe otherwise, but every one of those galaxies out there are forever inaccessible to us.

Yet there they are, we can see them. Sure, they are snapshots of the past and almost all of them are moving away from us (Andromeda and Milky Way are going to collide, though) but still: there they are. They're there. Was there life in them? I think it's crazypants to think not. Is there life still? Same answer. Might we know? Well, at any given time, some galactic-level civilization out there might be using some unfathomable tech and resources to create a signal observable beyond their galaxy. Personally, I think the odds that we will be around to look long enough to see such a thing — which itself would most likely be fleeting in cosmological time scales —is extremely unlikely. But we can safely assume, I think, that there is both life and intelligence in many or most of those galaxies. We'll never know.

What isn't two million or two billion light years away are the other stars and planets in our own galaxy. From edge-to-edge, light takes "only" 105 thousand years to cross it. But that's a 100 billion stars. We now know planets are common. Even if rocky planets in the goldilocks zone aren't so common, the apparent ubiquity of planets implies there are still quite a few. And life? I think we'll discover that life pops up in places outside an Earth-like environment, so surely there's life out there in our galaxy. Intelligent life? At any one time? Mayyybe. That we and another overlap in time and advancement enough to meet? Probably not, but maybe. Our stellar neighborhood in this section of our galaxy is vast yet still possibly within our reach. If we're lucky.

But beyond our galaxy? Everywhere else? All of those hundreds of billions of galaxies in the observable universe? Each containing billions to trillions of stars, each (mostly) surrounded by planets? Optimistically, if somehow, implausibly, a nearby satellite dwarf galaxy or even Andromeda might be a reachable destination in some mind-boggling effort . . . basically everywhere else will still be beyond our reach. I think an intergalactic technological species is so unlikely it probably hasn't happened yet in the history of the universe. It's only been almost 14 billion years, after all.

So, forever outside our reach, most likely.

But we can see those galaxies. We can study them. We can learn things about them. How amazing is that?
posted by Ivan Fyodorovich at 8:32 AM on July 13, 2022 [9 favorites]


We are able to differentiate ourselves, living, from the concept of life. We can't help an egocentric effort to define life elsewhere.

We are all fascinated looking at pictures of the universe's far past. Pictures of our sun, ~9 minutes ago, Webb's pictures, ~13 billion years ago. What happened is written on light coming our
way, by description a tiny swath of the story the light tells, in a scope beyond our ability to find a record of the middle or current state. We can't surf our own solar system in real time, with some of the cohorts so near and yet so far away.

This whole event has the feel of a huge, earthly family, gathered around the photo album, to look at the images of now passed ancestors. The sense of wonder, awe, connection, and recollection is the best public event in the world right now.

As they say, "It is written."
posted by Oyéah at 8:53 AM on July 13, 2022


Now I want to see a scale model image of our solar system put into the Southern Ring Nebula picture.
posted by clawsoon at 9:22 AM on July 13, 2022


If — and that's a huge "if" — humans are ever able to travel to another star, maybe even hundreds of light years away, we will never, ever travel to another galaxy

Funny thing about that...

If it were possible to build a spacecraft that accelerated at 1G continuously, a crew could in fact reach any location in the universe currently within the range where the universe's rate of expansion does not exceed the speed of light (some of the larger voids would be uncrossable), assuming they were reasonably young when they set out and had a normal lifespan. Special relativity is weird, yo.

Of course, we here on earth would be left in the dark about what happened to our intrepid crew unless it was a rather short trip. Still, they could easily make it anywhere within the local group within a lifetime. Much, much farther if they were content with "just passing through".
posted by wierdo at 9:45 AM on July 13, 2022 [1 favorite]


If it were possible to build a spacecraft that accelerated at 1G continuously

sooooo... what does the power requirements graph for that craft look like?
posted by clawsoon at 9:57 AM on July 13, 2022 [1 favorite]


Don't want to side track entirely into discussing science fiction, but I suspect that sci fi's broad use of "our galaxy" as a stand in for "interstellar space" in general is exactly because many people, and particularly most people who choose to write space-based science fiction, are very aware of how much harder it would be to get to another galaxy than it would be to get to another star even on the opposite side of this one.

Not that either is a walk down to the corner, of course.
posted by Ipsifendus at 10:42 AM on July 13, 2022 [3 favorites]


”Still, they could easily make it anywhere within the local group within a lifetime.”

Their lifetime(s), of course. Not ours. It takes at least 2.5 million years to get to Andromeda as far as we're concerned, no matter how closely they approach the speed of light. I don't think "we" sensibly includes both us and this hypothetical ship.

You know that, I recognize. But I feel it's important to grasp how such deep time makes the length of our existence as a species momentary by comparison.
posted by Ivan Fyodorovich at 11:43 AM on July 13, 2022 [1 favorite]


But we can see those galaxies. We can study them. We can learn things about them. How amazing is that? More amazing than I can put into words, to be honest.
posted by dg at 2:22 PM on July 13, 2022 [1 favorite]


The pretty images are great, but I'm very blown away by the black hole it found in the center of a galaxy in Stephan's Quintet. It can tell at a glance what elements are around the black hole and how fast things are moving around the black hole.

There's a common empty point in those images which sure seems like the black hole to me.

All this from a quick look taken mostly because it's a pretty formation, probably in less than a day. Compare with the few previous black hole images by radio telescopes, which have involved tremendous amouts of work and analysis.
posted by joeyh at 3:35 PM on July 13, 2022


"Expansion" doesn't require "expansion into", for example.

Ivan, do you have a real-world example of this I could read about? I'm being sincere. I would like to further educate myself on the subject.

And please don't take this the wrong way, but I'm not asking for a pure mathematical abstraction that models something we can't otherwise explain or makes inferences we can't actually falsify. I've got topology textbooks in my own library that already trip me out (not claiming to fully understand them, just saying that I already have them to reference when it comes to theory).

But I'm wondering whether we have directly measured the boundaries of anything (so that we have actual evidence the boundaries didn't change scope), that we have subsequently directly observed all of the individual constituents of (at a reasonable, observable scale) continuously growing further apart in every direction across its entire domain simultaneously without ever moving into an adjacent domain, doubling over itself, or compressing constituents at any point (so that we have real evidence that it is actually expanding and not simply shifting internally on a scale we can't observe)?

I'm not asking because I disbelieve you have read (or observed?) this, or even because it would entirely shock me to find out that we have strong evidence for that claim (it seems like every year I come across some new proof that the universe is infinite at least in strangeness).

I'm asking because mathematics is the language of physics. And like any language, no given statement in that language need be true in any meaningful sense or escapes the burden of proof. So if we have come across proof of such a thing in a real-world application, I would be delighted to read about it and have my meager understanding of the world expanded yet again. Thanks!
posted by It's Raining Florence Henderson at 4:15 PM on July 13, 2022 [2 favorites]


joeyh: the accreting black hole they got a spectrum of was well-known before (see, for instance, this paper). JWST lets you observe it in different ways but didn't discover it.

It wouldn't correspond to a dark spot in the images, in any event (you need to go to extreme levels of detail -- only possible via the Event Horizon Telescope today -- to see a black hole's shadow). In a JWST image, an accreting black hole would actually look much like a star, with the tell-tale diffraction spikes that were discussed above, as there is a lot of light coming from a very compact region of space, smaller than the smallest details the telescope can make out (stars show the spikes for the same reason).
posted by janewman at 4:37 PM on July 13, 2022 [2 favorites]


In a JWST image, an accreting black hole would actually look much like a star, with the tell-tale diffraction spikes that were discussed above, as there is a lot of light coming from a very compact region of space, smaller than the smallest details the telescope can make out (stars show the spikes for the same reason).

This is one of the reasons why I'm having a hard time understanding why gravitational lensing couldn't bend light back to as much as 180 degrees from its source.

I can understand the part about the accretion disk, that black holes are bright objects due to the accretion disk tearing apart other stars or bending light, and how not all light that approaches a black hole means that its going to fall below the event horizon and unable to escape.

I also don't think it would be easy or trivial to try to use gravitational lensing to look for and confirm that what looks like two different galaxies at two different points in time are the same galaxy.

And please note, I'm not talking about the wikipedia page I quoted above that light can transit the whole universe and come back at us from the other side. Right now I'm talking about gravitational lensing long after the Big Bang and expansion/inflation period, in our current relative time, give or take a few billion years. IE, long after the formation and condensation of galaxies and the development of supermassive galactic black holes.

And, sure, it's extremely likely I'm totally wrong about this and just not getting it, but logically it seems like it would be possible for photons from a given galaxy or source to be able to be bent so much that they meet or exceed 180 degrees of translation and eventually head back towards their source, even if they have to be lensed by multiple gravity wells, not just one black hole.

If gravitational lensing can bend light as much as we've already seen examples of just from incidental and more mild cases where you can see two or more warped copies of the same galaxy from I don't understand why those effects couldn't be stacked.

And since we've already seen so many examples of gravitational lensing in the Hubble and now JWST deep field imagery, it also makes sense to me that some or many of the naked eye visible clusters and galaxies that simply appear to us as bright, fuzzy stars that a given number of them are actually lensed duplicates from the same source.

In any case I still think we're going to find some useful examples of galaxies where our view of them have been split by gravitational lensing and we'll get to see and study them at two different points of relative time due to relativity and a difference in time for how long the light took to reach us around that gravitational lens.

Like how fucking cool would it be to be able to study and observe the evolution of a galaxy over a few million, hundred million or a billion years or so and have multiple snapshots of it all in the same image and frame and you were able to use some advanced image processing to take an educated guess about how to de-convolute it to compare them more accurately?

I also still have really strong feelings that the universe is even weirder than we currently think it is and more than we can see or observe directly mired in our own relativistic framework without accounting for more than 3+1 dimensions.
posted by loquacious at 5:50 PM on July 13, 2022


The extreme bending of light is why the EHT images of the two black holes that have been observed is why they both look like we are viewing them from the top/bottom at first glance, and not edge on.

Closer examination can reveal whether or not it's actually edge on through various effects. (differences in redshift and relativistic beaming causing one side to be brighter than the other are the two that come immediately to mind)

And yes, I do believe we have actually imaged galaxies where gravitational lensing produces multiple images of the same galaxy at different times due to the differing path lengths, though I don't believe that the few instances that have been found had a dramatic difference in age. I seem to recall one instance being confirmed when there happened to be a supernova in the lensed galaxy. I forget exactly how long the delay was, but I think it was a few weeks or months, not like years.

One of the really neat things about modem astronomy is that a lot of the data from repeated all sky surveys designed to catch supernovae (and a lot of other projects) are available for anyone to download and analyze themselves, and the toolchains necessary to do that analysis are often also freely available. Get your citizen science on and you might just find longer time delays.
posted by wierdo at 6:33 PM on July 13, 2022 [1 favorite]


But that doesn't make any sense since the universe isn't old enough for two objects to be that far apart (causally separated) from each other. Do you know how this gets reconciled in modern cosmology?

This may have been answered in replies I skipped but, due to the expansion of the universe, things that are currently causally connected (or have been in the past) can exit the observable universe. That is, things that once had a causal connection stop having one.

The edge of the observable universe is finite and distant things are slipping out of it into what you might call the unobservable universe. We don’t know whether that’s finite or not.

There are interesting parallels between the edge of the observable universe and a black hole event horizon, but a key difference is that the edge of the observable universe depends on where you are and AFIK (and subtle if so) the black hole event horizon does not.

But it is certainly the case that two things we can see at opposite sides of our observable universe cannot see each other anymore.
posted by sjswitzer at 6:40 PM on July 13, 2022 [3 favorites]


wierdo: yeah, the time delay for the first lensed supernova was about a year. There are also at this point many measurements of time delays between multiple lensed images of quasars (the brightness of a quasar varies with time as material accretes onto the supermassive black hole at varying rates, and you can see the same pattern of time variations show up on different dates in different images).

The gravitational lensing caused by galaxies is a lot less than 180 degrees -- typically, we're looking at deflections of light by a few arcseconds (a full moon is ~2000 arcseconds across -- this is a tiny amount). You need really, really intense gravity (i.e., something really dense) to get deflections that big -- which is exactly what happens around black holes (the rings around the black hole 'shadows' that the Event Horizon Telescope has observed consist of light that's been very strongly lensed, as wierdo described).

We don't yet have the capability of making measurements with sufficient precision to see the distance of a faraway object change with time directly (what are called 'redshift drift' measurements). However, there are a number of ideas of ways to do this that may bear fruit in the 2030s.
posted by janewman at 7:58 PM on July 13, 2022 [3 favorites]


By the way, loquacious: because the deflections by gravitational lensing from galaxies and galaxy clusters that we observe aren't that big, the time delays between multiple images won't be large enough to see real evolution between them. Order of magnitude: a huge deflection would be 30 arcseconds, or 1/120th of a degree, or about 10^-4 radians, in which case you'd expect time delays of order 0.01% of the path length between the multiple images. For a faraway galaxy that would be of order a million years; the shortest timescales on which galaxies can change significantly are more like 100 million years.
posted by janewman at 8:04 PM on July 13, 2022 [3 favorites]


Question: when making observations on the structure of the CMB how much do lensing effects, across the entirety of the visible universe, need to be accounted for? There must be an innumerable number of such ‘lenses’ in all directions between us and the CMB. Can they meaningfully perturb our observations or can we ignore them?
posted by Insert Clever Name Here at 6:43 AM on July 14, 2022


(After further consideration I’m going to go with ‘ignore’, if the CMB is even affected by gravity like this.)
posted by Insert Clever Name Here at 7:36 AM on July 14, 2022


Insert Clever Name Here: definitely not ignore. The CMB we see is affected by lensing, particularly on small angular scales; in fact, a major goal for future CMB projects is to measure that lensing with high precision (the lensed CMB signal has statistical characteristics that allow you to distinguish it from what the unlensed CMB should look like, as well as to remove the lensing effect). That will provide maps of the total amount of mass in the foreground of the CMB along each line of sight, basically.

You can find a little about CMB lensing measurements to date here.
posted by janewman at 8:46 AM on July 14, 2022 [3 favorites]


Thanks! This thread has been the occasion for a lot of new learning about the cosmos for me, all of which might never have happened if Webb had not turned out so successfully. I for one am totally satisfied with whatever contribution my personal tax dollars made to the project. (Probably quite infinitesimal…which seems somehow appropriate.)
posted by Insert Clever Name Here at 9:04 AM on July 14, 2022 [4 favorites]


The extreme bending of light is why the EHT images of the two black holes that have been observed is why they both look like we are viewing them from the top/bottom at first glance, and not edge on.

One or another of the reputable science youtubers had a thing about this, and (just because wierdo didn't explicitly say this) you can indeed have light do a 180 (or close to) around a black hole, and (in Interstellar) this gives us the thin halo around the black hole inside the accretion disk. But this can only happen to photons that hit in a narrow band just outside... I want to say the photon sphere?
posted by GCU Sweet and Full of Grace at 9:06 AM on July 14, 2022


That was in this video: https://www.youtube.com/watch?v=Q1bSDnuIPbo
posted by DreamerFi at 9:35 AM on July 14, 2022


This video has a nice animation illustrating how light paths get deflected around a black hole, in an extreme case of gravitational lensing.
posted by janewman at 9:58 AM on July 14, 2022 [1 favorite]


Whenever life gets you down, Mrs.Brown
And things seem hard or tough
And people are stupid, obnoxious or daft
And you feel that you've had quite enough

Just remember that you're standing on a planet that's evolving
And revolving at nine hundred miles an hour
That's orbiting at nineteen miles a second, so it's reckoned
A sun that is the source of all our power

The sun and you and me and all the stars that we can see
Are moving at a million miles a day
In an outer spiral arm, at forty thousand miles an hour
Of the galaxy we call the 'Milky Way'

Our galaxy itself contains a hundred billion stars
It's a hundred thousand light years side to side
It bulges in the middle, sixteen thousand light years thick
But out by us, it's just three thousand light years wide

We're thirty thousand light years from galactic central point
We go 'round every two hundred million years
And our galaxy is only one of millions of billions
In this amazing and expanding universe

The universe itself keeps on expanding and expanding
In all of the directions it can whizz
As fast as it can go, the speed of light, you know
Twelve million miles a minute and that's the fastest speed there is

So remember, when you're feeling very small and insecure
How amazingly unlikely is your birth
And pray that there's intelligent life somewhere up in space
'Cause it's bugger all down here on Earth
posted by Abehammerb Lincoln at 3:10 PM on July 14, 2022 [4 favorites]


After reading Insert Clever Name Here's commentary in this thread, this is how I feel times ten, squared and cubed.

Boy, talk about hurting Hulk head.
posted by y2karl at 3:42 PM on July 14, 2022


janewman, webb is not directly imaging the black hole. But as Dr Becky Smethurst described it "you can see that this hydrogen has made this ring around the supermassive black hole. [...] We have never ever seen data like that before"
posted by joeyh at 9:27 PM on July 15, 2022 [1 favorite]


Thank you to everyone calling it JWST … this is in response to NASA naming it for a man who actively sought out gay workers to get them outed and/or fired. All of you people are so d*mn smart. Awesome humans, awesome universe.
posted by beckybakeroo at 12:10 AM on July 16, 2022 [3 favorites]


joeyh: that ring has to be much larger in radius than any of the structures the Event Horizon Telescope sees (and thus much, much larger than the event horizon that is the limit for where light can escape, or the accretion disk around the black hole, for that matter). It's hard to tell exact values from a press release image, but the smallest details JWST could make out at the distance of Stefan's Quintet at that wavelength would be hundreds of light-years across. In comparison, the radius of the event horizon for the very largest black holes (which is not what the modest-mass galaxies in the Quintet would host) are of order a light-day.

So basically it would seem this is a molecular ring in a disk of gas at the center of the galaxy (and at a radius where a black hole would have only a minor influence on the local gravity compared to stars). Such molecular rings are seen in the disks of spiral galaxies sometimes (including, quite possibly, the Milky Way).
posted by janewman at 2:50 PM on July 16, 2022 [1 favorite]


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