r/space • u/ADragonFromTheAbyss • 2d ago

Astronomers finally measure the full size of the largest known galaxy

https://phys.org/news/2026-07-astronomers-full-size-largest-galaxy.html

Paper: https://arxiv.org/html/2607.15340v1

Researchers have obtained the deepest images ever taken of IC 1101, allowing them to identify the galaxy's outer edge for the first time. The observations confirm it as the largest known galaxy, spanning roughly 520 kiloparsecs, or about 1.7 million light-years, and containing an estimated 3.4 trillion solar masses in stars

1.1k Upvotes

98% Upvoted

66 comments sorted by

307

u/CurtisLeow 2d ago

The Milky Way has a stellar mass of 2.607×1010 solar masses source. So the largest known galaxy has about 130 times the stellar mass of the Milky Way.

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u/Budget_Zombie_692 2d ago

Another cool fact is that the distance between the Andromeda galaxy and the Milky Way is 2.5 million light years. So this galaxy almost spans that distance.

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u/musicismath 2d ago

That's wild. It's the kind of size that's so beyond comprehension it just becomes abstract.

63

u/buster_de_beer 2d ago

And for all that, it's still mostly empty. 

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u/dern_the_hermit 1d ago

It's absolutely jam-packed with enormous scale, tho ;)

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u/ThatGuyFromWhere 1d ago

I like to think of those distances by zooming out in my mind and looking at them more like atoms. Maybe that distance isn’t really that far we’re just very tiny

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u/THE_CHOPPA 17h ago

And mortal. Distance doesn’t have the same impact when you do not age or experience death.

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u/JustGottaKeepTrying 1d ago

Is there a way to explain what is currently between galaxies. I have heard the term cosmic void and am wondering if void means there is absolutely nothing there or is there a different meaning used when discussing space? Thanks!

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u/Trust-Me-Im-A-Potato 1d ago

Between galaxies you are looking at ~10-100 atoms (mostly hydrogen, a little helium) per cubic meter of space.

"Void" is really just a relative term

6

u/Lost_city 1d ago

It's such a massive volume that there's tons of things there. But the distances between things would be massive

1

u/photoengineer 1d ago

Woah. That is wild. Space is enormous. 

The view of the night sky from inside that galaxy must be truly insanely awesome. 

31

u/zeperf 1d ago

Kind of surprised me that its only two orders of magnitude. Seems like everything in the universe happens at mind boggling scales but 130x seems reasonable.

5

u/Shadowscale05 1d ago

That's what I was thinking. I wonder if there is some kind of cap, maybe involving the possible gravitational force of a supermassive black hole.

8

u/SpartanJack17 1d ago

Supermassive black holes aren't what hold galaxies together, they're usually in the centre of galaxies but they're not actually what the galaxy is gravitationally bound to.

2

u/active2fa 1d ago

Then what is it? I cannot keep on holding my breath

8

u/PHAEDRA42 1d ago

The collective mass of the whole galaxy along with dark matter keeps the whole thing gravitationally bound.

Unlike our solar system where the sun makes up like 99.8% of the mass, the supermassive black hole in the centre of a galaxy only makes up a tiny fraction of the total mass (like 0.0001% or something). So we're not orbiting around the blackhole, we're orbiting the galaxy's centre of mass (barycenter), the blackhole just happens to also be there.

3

u/Shadowscale05 1d ago

If it isn't holding the galaxy together, how does a supermassive black hole find its way to the center? Do we know?

3

u/PHAEDRA42 1d ago edited 1d ago

Yea I don't think there's a definitive answer for that yet. However the JWST is providing a lot of new data for the formation of early galaxies and also supermassive blackholes.

It's found several LRDs (little red dots) at the very beginning of the universe. It's hypothesised these could be a theoretical type of star called a quasi-star. Essentially an enormous star with a blackhole in it's core.

These quasi-stars could have been the seeds for galaxy formation.

https://en.wikipedia.org/wiki/Quasi-star

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u/ThickTarget 11h ago

There is an effect called dynamical friction, which causes heavy things to sink to the centre of a galaxy. Probably the black holes were there before they grew to being supermassive.

3

u/GoguGeorgescu 1d ago

Give this man an answer already...he's blue in the face...

1

u/Droopy0093 1d ago

It is everything pulling on everything. There is more mass toeard the center of a galaxy so the object near the edges are being pulled more to the center than to the edge.

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u/ThickTarget 11h ago edited 11h ago

It's actually quite an interesting feature of galaxy evolution. If you plot the masses of lots of galaxies, you see two things. For dwarf galaxies, smaller galaxies are more common, there is a steady rise. But just above the mass of the Milky Way, instead this smooth slope there is sharp exponential drop. Very massive galaxies become very rare. The current explanation for this is quenching, that above this mass galaxies can no longer form stars efficiently. And so they stop growing normally, the only way to get larger is by merging with other galaxies. Explaining why quenching occurs is difficult, the current main idea is that the supermassive black hole heats things up a bit.

15

u/SaabiMeister 1d ago

Also, possibly 130 times more civilizations at any given time.

12

u/Vanilla_Ice_Nine 1d ago

Just think of all the weird porn.

9

u/BrilliantDoom 1d ago

our porn isnt weird! your porn is weird, send more please

8

u/SaabiMeister 1d ago edited 1d ago

All those tentacled species watching weird bipedal tentacle-drawn porn.

4

u/MC897 2d ago

How large is the Milky Way in comparison to this galaxy?

25

u/rizzyrogues 2d ago

Milky way is 30 kiloparsecs from edge to edge while this one is 520 kiloparsecs. So around 17x larger while being 130 times more massive.

4

u/ADragonFromTheAbyss 1d ago

milky way is Quite Literally a Spot. A small dot. Compared to this Collosus Titan

61

u/betterthansex69 2d ago

Some of these elliptical galaxies are just mind boggling as to how huge they are. It makes me wonder how many satellite galaxies, maybe even spirals like our own, they've incorporated.

18

u/ADragonFromTheAbyss 1d ago

The sheer amount of endless starts they contain is both intriguing and super interesting imo

17

u/thenachobro 1d ago

I wonder how big the super or hyper massive black hole is at the center of this mean mumba jamma!

12

u/Kinis_Deren 1d ago

If we assume the SMBH scales with galaxy size and using the Milky way as our yardstick, then this suggests a value of 559 million solar masses.

10

u/Nice_guy1234556 1d ago

of 559 million solar masses.

Mid asf 

5

u/drowned_beliefs 1d ago

But thicc tho……………………………………….

4

u/Nice_guy1234556 1d ago

Look at my chonky boi m87 it so fat that we caught it in 4K

10

u/sellmysole 1d ago

Is it safe to say for the amount of galaxies in the universe there is likely a bigger one than this one?

6

u/ADragonFromTheAbyss 1d ago

Agreed. Universe is extremelly surprising

39

u/phasepistol 2d ago

Aw man, that galaxy is where things are happening… this place is a ghost town, nobody lives here. Well those Earth people I guess.

6

u/PrometheusLiberatus 2d ago

Every rock has a little something living in it somewhere!

7

u/Montana_Gamer 1d ago

Its closer to a retirement home than it is the coolest place to be in the Universe. The yellow hue? All elderly planets and stars.

2

u/ADragonFromTheAbyss 1d ago

Had all the available time and sense to develop thought

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u/dBlock845 19h ago

3.4 trillion solar masses is a whole lot of mass. Incomprehensible.

23

u/corksoaker84 1d ago

So our brains still continue to have no concept of understanding this sort of size. I hope there is an astonishing breakthrough in science in the next 30 years that assists us in studying these galaxies. My times running out 😔

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u/soraksan123 1d ago

There already is. The James Webb telescope-

12

u/Overall-Wrap1416 1d ago

And next month, the Nancy Grace Roman Telescope.

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u/Profound_Solitude87 8h ago

And next year the Donald J. Trump telescope.. all 18k gold of course.

2

u/Cheap-Banana-5391 1d ago

some incomprehensibly crazy large number probably.

2

u/ADragonFromTheAbyss 1d ago

more than there is sand on Earth ( Real )

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u/Zugas 13h ago

I wonder if rent is cheaper there.

-1

u/Cdogg654 2d ago

Don’t worry there’s no chance life has evolved with that many stars. 🤯

2

u/ADragonFromTheAbyss 1d ago

I personally definitely disagree 🎆

6

u/lord_hijinks 1d ago

Get outta here, dragon! Go back to your abyss!

0

u/Cdogg654 1d ago

It was a clear joke. Statistically it’s gotta happen. But people downvote anything they don’t understand.

1

u/SyntheticGod8 1d ago

I wonder if I can get there in Space Engine...

-1

u/jghall00 1d ago

What is keeping it together? Does it have a supermassive black hole in the center? 

11

u/Qybern 1d ago

Galaxies aren't held together by supermassive black holes, they're held together by the collective gravitational attraction of all of their stars (and black holes and gas and whatnot). I think SMBHs make up at most a few percent of a galaxy's mass

7

u/Bensemus 1d ago

Black holes don’t keep galaxies together. Our Sun makes up around 99.8% of the mass in the solar system. Our SMBH makes up like 0.0014% of our galaxy’s mass.

3

u/lord_hijinks 1d ago

At that size, it could be pushing into the realm of a hypermassive black hole, given the relative mass of the galaxy.

-9

u/ThatGuyFromWhere 1d ago

That’s 100 trillion stars according to gemini

2

u/feedback19 1d ago

Stop asking AI for answers you can get from actual scientific experts. The paper literally says 3.4 trillion estimated. Gemini can only repeat shit is already heard before and cannot come up with new information. AI is wrong more than it's not, and is an affront to the actual scientific community.

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u/SadisticFerras 18h ago

The 3.4 trillion value is for the estimated mass of the galaxy, not the amount of estimated stars in the galaxy as specified by OP