<p>I think, by his mention of asteroids, that the OP means an object in the scale of asteroids or dwarf planets, that is, almost-solid objects. In this case, asteroids the size of 2 Pallas or 4 Vesta are ellipsoids, and smaller than that, we have 511 Davida which is the biggest clearly non-spherical asteroid:</p>

<p><img src="https://i.sstatic.net/9jPuo.jpg" alt="enter image description here"></p>

CC BY-SA 3.0
2015-02-01T19:57:54.593Z
@Haaakon Near Earth and Mars crossing [1620  Geographos](https://en.wikipedia.org/wiki/1620_Geographos) deserves mentioning because it seems to be the most elongated asteroid known at 5.1 x 1.8 km.
LocalFluff
CC BY-SA 3.0
2014-01-10T01:02:28.013Z
2014-01-10T01:02:28.013Z
Envite
<p>In the same vein as @arne's answer, this just in from Slashdot: <a href="http://science.slashdot.org/story/13/11/15/003222/astronomers-discover-largest-structure-in-the-universe" rel="noreferrer">Astronomers Discover Largest Structure In the Universe</a>, <a href="https://medium.com/the-physics-arxiv-blog/267ddcb8057b" rel="noreferrer">linked article</a> and <a href="http://arxiv.org/abs/1311.1104" rel="noreferrer">the original</a> - <strong>10 billion light years across</strong>, based on data from gamma-ray bursts.</p>
<blockquote>
<p><strong>So this thing, presumably another wall of even more distant galaxies, is the new largest structure in the universe.</strong></p>
<p>One of the fundamental tenets of cosmology is the Cosmological principle—this holds that the distribution of matter in the universe will appear uniform if viewed from a large enough scale.</p>
<p>At whatever scale they look, large scale structures always seem to emerge.</p>
</blockquote>
<p>(I haven't seen a name associated with it yet.)</p>

CC BY-SA 3.0
2013-11-15T10:27:15.720Z
2014-09-11T17:42:29.587Z
2020-06-17T09:47:40.653Z
aneroid
<p>The largest non-spherical objects which are virialized (meaning essentially dynamically relaxed; not in the process of forming or collapsing) are super clusters of galaxies (<a href="http://en.wikipedia.org/wiki/Supercluster#Nearby_superclusters" rel="noreferrer">here is a list of nearby super clusters</a>). They're the most massive objects before you must begin to consider large scale structures like filaments. </p>

<p>These objects are largely non-spherical. Most of them happen to be <a href="http://en.wikipedia.org/wiki/Ellipsoid" rel="noreferrer">tri-axial ellipsoids</a> (either footballs, frisbees, or somewhere in between) due to the nature of large scale structure formation occurring along two axes at different times.</p>

<p>If you think tri-axial ellipsoids are just spheres squashed in certain ways (and that therefore clusters don't really count as "non-spherical"), then the answer would be filamentary structures (both the most massive, and the largest in scale). Here's an image from the Millennium Simulation to show what a super cluster would look like:</p>

<p><img src="https://i.sstatic.net/JdmmE.jpg" alt="enter image description here"></p>

CC BY-SA 3.0
2013-11-15T13:39:36.700Z
2013-11-15T13:39:36.700Z
astromax
<p>If you count conglomerates of galaxy style objects, the largest structure in the universe so far is the <a href="http://en.wikipedia.org/wiki/Huge-LQG" rel="nofollow noreferrer">Huge Large Quasar Group</a>.</p>

<p>It seems to be four billion ly in size, and contains dozens of Quasars, which in turn are very active galactic nuclei.</p>

<p><img src="https://i.sstatic.net/DJv9R.png" alt="enter image description here"></p>

CC BY-SA 3.0
2013-11-15T08:50:44.383Z
2013-11-15T08:50:44.383Z
Arne
<p>Let me see, some objects are listed because of their records. First, nebulae, which are huge clouds of dust and gas. The largest in the Milky Way's neighborhood is the Tarantula Nebula (30 Doradus, NGC 2070 or Caldwell 103).:</p>
<p><img src="https://2.bp.blogspot.com/_viputHRpZ2A/SRL1YHQxmKI/AAAAAAAABSY/IQN4-D4FClY/s400/NGC+2070+by+Joe+Brimacombe.jpg" alt="Tarantula Nebula" /></p>
<p>This is the largest nebula in the Milky Way's neighborhood, at 300 light-years (almost 100 pc). But if we are in the universal record, that would be NGC 604, which is 740 light-years (240 pc) across.:</p>
<p><a href="https://i.sstatic.net/RdfBm.jpg" rel="nofollow noreferrer"><img src="https://i.sstatic.net/RdfBm.jpg" alt="NGC 604" /></a><br />
<sub>(source: <a href="http://www.wolaver.org/Space/ngc604.jpg" rel="nofollow noreferrer">wolaver.org</a>)</sub></p>
<p>Next, galaxies, which come in different shapes. Spirals first, and what like called2voyage has said, is NGC 262. Because he can't provide a pic, I will!:</p>
<p><a href="https://i.sstatic.net/msj9f.jpg" rel="nofollow noreferrer"><img src="https://i.sstatic.net/msj9f.jpg" alt="NGC 262" /></a><br />
<sub>(source: <a href="http://cseligman.com/text/atlas/ngc262.jpg" rel="nofollow noreferrer">cseligman.com</a>)</sub></p>
<p>NGC 262 is a giant Seyfert spiral, and is 1.3 million light-years across, more than two times larger than the mistakenly clamed largest spiral last January 2013, NGC 6872.:</p>
<p><img src="https://www.nasa.gov/sites/default/files/images/718359main_composite_no_labels.jpg" alt="NGC 6872" /></p>
<p>I don't know why they claimed this one as largest, at 522,000 light-years across <em>only</em> is less than half as that of NGC 262.</p>
<p>But the hands-down king of all galaxies is IC 1101, at 5.6 million light-years across, and is the record holder since 1989.:</p>
<p><img src="https://4.bp.blogspot.com/-kFoYO-Y4AW4/T3_zoxObL8I/AAAAAAAAfH8/02vUYCn5q44/s400/ic_1101.jpg" alt="IC 1101" /></p>
<p>A size comparison of this monster:</p>
<p><a href="https://i.sstatic.net/hVh0B.jpg" rel="nofollow noreferrer"><img src="https://i.sstatic.net/hVh0B.jpg" alt="IC 1101 vs. Milky Way and other galaxies" /></a><br />
<sub>(source: <a href="https://astrobob.areavoices.com/files/2013/07/IC-1101-compared-to-Milky-Way1-1024x563.jpg" rel="nofollow noreferrer">areavoices.com</a>)</sub></p>
<p>Next, structures. aneroid has the right answer. It's name is Hercules-Corona Borealis Great Wall, some 10 billion light-years across.</p>

CC BY-SA 3.0
2014-09-14T16:54:26.487Z
Good answer, but are you sure the last graphic is correct? The Milky Way and Andromeda are much closer in size.
HDE 226868
CC BY-SA 4.0
2013-12-17T09:49:35.710Z
2019-02-16T12:50:16.720Z
2020-06-17T09:47:40.653Z
user624
<p>All these answers are, of course, correct. I only want to make a simple observation. According to the definition linked in the OP, an <em>astronomical object</em> is gravitationally bound. So we are looking for the largest gravitationally bound object.</p>

<p>If the universe were closed, it's bound and hence the largest astronomical object ;-)</p>

<p>However, it appears the universe is expanding forever and hence not bound. The largest bound objects are galaxy clusters and galaxy super clusters. These objects have just formed or are still forming: the dynamical (orbital) time scale at their outskirts is comparable to the age of the universe.</p>

<p>Thus, the largest bound objects will be larger if you wait a few giga years ...</p>

CC BY-SA 3.0
2014-01-09T18:56:52.167Z
2014-01-09T18:56:52.167Z
Walter
<p>The largest "complex, less cohesively bound structure, which may consist of multiple bodies or even other objects with substructures" known object is the <a href="https://en.wikipedia.org/wiki/Shapley_Supercluster" rel="nofollow noreferrer">Shapley Supercluster</a>, which comprises 76000 galaxies. It is supossed that <a href="https://es.wikipedia.org/wiki/Laniakea" rel="nofollow noreferrer">Laniakea</a> (our own supercluster) moves towards it and both may be part of a bigger structure, yet to be confirmed.</p>

CC BY-SA 4.0
2019-06-06T11:30:03.393Z
2019-06-06T11:30:03.393Z
Envite
<p>Well, this is my relatively inaccurate size comparison of galaxies. IC 1101 is 6 million LY at this scale, NGC 263 is 2.3 million LY, and there are some other galaxies.</p>

<p><a href="https://i.sstatic.net/Vf8JK.png" rel="nofollow noreferrer"><img src="https://i.sstatic.net/Vf8JK.png" alt=""></a></p>

CC BY-SA 3.0
2016-06-11T03:59:35.347Z
2016-06-11T13:43:03.400Z
2016-06-11T13:43:03.400Z
Your Mom
<p>Warning: citations above about IC 1101 being the largest known galaxy are probably wrong! Wikipedia's claimed 5 Mly size is certainly incorrect.</p>

<p>The visible light extent is about 360 kly (<a href="http://ned.ipac.caltech.edu/cgi-bin/objsearch?objname=IC%201101&amp;extend=no&amp;hconst=73&amp;omegam=0.27&amp;omegav=0.73&amp;corr_z=1&amp;out_csys=Equatorial&amp;out_equinox=J2000.0&amp;obj_sort=RA%20or%20Longitude&amp;of=pre_text&amp;zv_breaker=30000.0&amp;list_limit=5&amp;img_stamp=YES#ObjNo1" rel="nofollow">NED's summary page</a> gives a major diameter of 1.2' and a redshift of z=0.077947, for a physical size of around 115 kpc, or 370 kly). The largest measurement one could reasonably suggest for IC 1101 (around 500 kpc, or 1.5 Mly) comes from the maximal measured extent of the diffuse light from Uson, Bough &amp; Kuhn (1991). That's not what one usually thinks of when talking about the "size" of a galaxy. Usually we refer to the radius in which most of the visible light is enclosed, not the maximum distance we could possibly measure light that might be associated with the galaxy.</p>

<p>Similarly, NGC 262 is not 1.3 Mly across. It has an extended cold Hydrogen gas halo of around 600 kly (~10' HI measurement from Morris &amp; Wannier 1979, distance ~65 Mpc), but the physical extent of its stars is around 66 kly: large for a spiral, but not huge.</p>

<p>To answer the question: I'd go with galaxy superclusters as being the largest currently gravitationally-bound objects in the universe.</p>

CC BY-SA 3.0
2014-12-12T06:27:16.490Z
2014-12-12T06:27:16.490Z
parejkoj
<p>The largest sub-galactic astronomical object (in volume) that we know of is the <a href="http://astropixels.com/diffusenebulae/NGC3372-03.html" rel="nofollow noreferrer">Carina Nebula</a>, which is a non-spherical <a href="http://en.wikipedia.org/wiki/Diffuse_nebula#Diffuse_nebulae" rel="nofollow noreferrer">diffuse nebula</a>. The Carina Nebula has a radius of about 100 parsecs.</p>

<p><img src="https://upload.wikimedia.org/wikipedia/commons/thumb/e/ea/Carina_Nebula.jpg/800px-Carina_Nebula.jpg" alt="Carina Nebula"></p>

<p><sub>Image credit: ESA</sub></p>

<p>If you consider astronomical objects of the galactic scale, then the galaxy <a href="http://en.wikipedia.org/wiki/IC_1101" rel="nofollow noreferrer">IC 1101</a> is the largest astronomical object (in volume) that we know of. From Wikipedia:</p>

<blockquote>
  <p>The galaxy has a diameter of approximately 6 million light years, which makes it currently (as of 2013) the largest known galaxy in terms of breadth. It is the central galaxy of a massive cluster containing a mass (mostly dark matter) of roughly 100 trillion stars. Being more than 50 times the size of the Milky Way and 2000 times as massive</p>
</blockquote>

<p>IC 1101 is on the left in the image below.</p>

<p><img src="https://upload.wikimedia.org/wikipedia/commons/thumb/c/cf/Abell_2029.png/800px-Abell_2029.png" alt="IC 1101"></p>

<p>Here is an image from the Sloan Digital Sky Survey (SDSS) of IC 1101:</p>

<p><img src="https://i.sstatic.net/oXRpD.jpg" alt="SDSS IC 1101"></p>

<p>I'll leave it to you to decide if an elliptical galaxy counts as "spherical" or not.</p>

<p>If you don't count elliptical galaxies, the largest spiral galaxy is <a href="http://en.wikipedia.org/wiki/NGC_262" rel="nofollow noreferrer">NGC 262</a>, pictured below. It has a diameter of 1.3 million light years.</p>

<p><img src="https://i.sstatic.net/Dlkuc.jpg" alt="NGC 262"></p>

CC BY-SA 3.0
2013-11-14T21:15:32.230Z
2014-01-09T20:02:04.507Z
2017-03-10T09:42:47.053Z
called2voyage
<p>Some asteroids and comets are non-spherical. But is the nature of big things and gravity so that large things in the universe are always spherical? What is the biggest astronomical object in terms of volume out there that's not spherical?</p>

<hr>

<p>Note: Astronomical object is a defined term. See <a href="http://en.wikipedia.org/wiki/Astronomical_object" rel="nofollow">Astronomical object - Wikipedia</a>.</p>

CC BY-SA 3.0
2016-06-11T16:29:00.917Z
Hi @Hakonbogen. You may have the wrong idea: almost everything in the universe is **NON** spherical. *"But is the nature of big things and gravity so that large things in the universe are always spherical?"* - indeed, absolutely NOT. Gravity likes to make filaments, and pancakes. Most things in the universe are the shape of our galaxy, or, filament-like. Only when you get down to exremely small scales, like planets, do you get spheres. Cont...
Fattie
CC BY-SA 3.0
2016-06-11T16:29:29.840Z
... Even planets "want" to not be spheres: they like having rings and so on. The Earth-Moon (which is a unit) is a dumbbell, very unlike a sphere. Our solar system is a flat disk; and so on. Almost nothing is a sphere!
Fattie
CC BY-SA 4.0
2019-02-17T16:38:52.463Z
Some supercluster, or more probably, the Bootes void.
Wayfaring Stranger
CC BY-SA 3.0
2013-11-14T20:12:21.807Z
**Hint:** The more an object spins, the less of a true sphere it is.
called2voyage
CC BY-SA 3.0
2013-11-14T20:25:54.860Z
Also, collisions and explosions can create some interesting shapes. I guess it depends on what you consider to be a single object. Nebulae are not spherical.
called2voyage
CC BY-SA 3.0
2013-11-14T22:09:35.087Z
Perhaps a better question is what is the largest (almost) spherical object?
Moriarty
CC BY-SA 3.0
2014-01-09T22:54:04.190Z
You may be interested in the hydrostatic equilibrium, which is where an object over time will become spherical due to its own gravity. This equilibrium is dependent on multiple factors such as density, temperature and diameter.
frodeborli
<universe>
What's the largest non-spherical astronomical object in the universe?
bogen
# What's the largest non-spherical astronomical object in the universe?

(Asked by: username_0 on 2013-11-14)

Some asteroids and comets are non-spherical. But is the nature of big things and gravity so that large things in the universe are always spherical? What is the biggest astronomical object in terms of volume out there that's not spherical?

---

Note: Astronomical object is a defined term. See [Astronomical object - Wikipedia](http://en.wikipedia.org/wiki/Astronomical_object).

**Tags:** universe
> **Comments:**
> **username_3**: **Hint:** The more an object spins, the less of a true sphere it is.  
> **username_3**: Also, collisions and explosions can create some interesting shapes. I guess it depends on what you consider to be a single object. Nebulae are not spherical.  
> **username_4**: Perhaps a better question is what is the largest (almost) spherical object?  
> **username_5**: You may be interested in the hydrostatic equilibrium, which is where an object over time will become spherical due to its own gravity. This equilibrium is dependent on multiple factors such as density, temperature and diameter.  
> **username_1**: Hi @Hakonbogen. You may have the wrong idea: almost everything in the universe is **NON** spherical. *"But is the nature of big things and gravity so that large things in the universe are always spherical?"* - indeed, absolutely NOT. Gravity likes to make filaments, and pancakes. Most things in the universe are the shape of our galaxy, or, filament-like. Only when you get down to exremely small scales, like planets, do you get spheres. Cont...  
> **username_1**: ... Even planets "want" to not be spheres: they like having rings and so on. The Earth-Moon (which is a unit) is a dumbbell, very unlike a sphere. Our solar system is a flat disk; and so on. Almost nothing is a sphere!  
> **username_2**: Some supercluster, or more probably, the Bootes void.  

---

## 10 answers

### Answer by username_3 on 2013-11-14. Score: 13 | Accepted answer

The largest sub-galactic astronomical object (in volume) that we know of is the [Carina Nebula](http://astropixels.com/diffusenebulae/NGC3372-03.html), which is a non-spherical [diffuse nebula](http://en.wikipedia.org/wiki/Diffuse_nebula#Diffuse_nebulae). The Carina Nebula has a radius of about 100 parsecs.

![Carina Nebula](https://upload.wikimedia.org/wikipedia/commons/thumb/e/ea/Carina_Nebula.jpg/800px-Carina_Nebula.jpg)

Image credit: ESA

If you consider astronomical objects of the galactic scale, then the galaxy [IC 1101](http://en.wikipedia.org/wiki/IC_1101) is the largest astronomical object (in volume) that we know of. From Wikipedia:

> The galaxy has a diameter of approximately 6 million light years, which makes it currently (as of 2013) the largest known galaxy in terms of breadth. It is the central galaxy of a massive cluster containing a mass (mostly dark matter) of roughly 100 trillion stars. Being more than 50 times the size of the Milky Way and 2000 times as massive

IC 1101 is on the left in the image below.

![IC 1101](https://upload.wikimedia.org/wikipedia/commons/thumb/c/cf/Abell_2029.png/800px-Abell_2029.png)

Here is an image from the Sloan Digital Sky Survey (SDSS) of IC 1101:

![SDSS IC 1101](https://i.sstatic.net/oXRpD.jpg)

I'll leave it to you to decide if an elliptical galaxy counts as "spherical" or not.

If you don't count elliptical galaxies, the largest spiral galaxy is [NGC 262](http://en.wikipedia.org/wiki/NGC_262), pictured below. It has a diameter of 1.3 million light years.

![NGC 262](https://i.sstatic.net/Dlkuc.jpg)


---

### Answer by username_6 on 2014-01-10. Score: 10

I think, by his mention of asteroids, that the OP means an object in the scale of asteroids or dwarf planets, that is, almost-solid objects. In this case, asteroids the size of 2 Pallas or 4 Vesta are ellipsoids, and smaller than that, we have 511 Davida which is the biggest clearly non-spherical asteroid:

![enter image description here](https://i.sstatic.net/9jPuo.jpg)

> **Comments:**
> **username_7**: @Haaakon Near Earth and Mars crossing [1620  Geographos](https://en.wikipedia.org/wiki/1620_Geographos) deserves mentioning because it seems to be the most elongated asteroid known at 5.1 x 1.8 km.  

---

### Answer by username_8 on 2013-11-15. Score: 9

In the same vein as @arne's answer, this just in from Slashdot: [Astronomers Discover Largest Structure In the Universe](http://science.slashdot.org/story/13/11/15/003222/astronomers-discover-largest-structure-in-the-universe), [linked article](https://medium.com/the-physics-arxiv-blog/267ddcb8057b) and [the original](http://arxiv.org/abs/1311.1104) - **10 billion light years across**, based on data from gamma-ray bursts.

> **So this thing, presumably another wall of even more distant galaxies, is the new largest structure in the universe.**
>
> One of the fundamental tenets of cosmology is the Cosmological principle—this holds that the distribution of matter in the universe will appear uniform if viewed from a large enough scale.
>
> At whatever scale they look, large scale structures always seem to emerge.

(I haven't seen a name associated with it yet.)


---

### Answer by username_9 on 2013-11-15. Score: 7

The largest non-spherical objects which are virialized (meaning essentially dynamically relaxed; not in the process of forming or collapsing) are super clusters of galaxies ([here is a list of nearby super clusters](http://en.wikipedia.org/wiki/Supercluster#Nearby_superclusters)). They're the most massive objects before you must begin to consider large scale structures like filaments.

These objects are largely non-spherical. Most of them happen to be [tri-axial ellipsoids](http://en.wikipedia.org/wiki/Ellipsoid) (either footballs, frisbees, or somewhere in between) due to the nature of large scale structure formation occurring along two axes at different times.

If you think tri-axial ellipsoids are just spheres squashed in certain ways (and that therefore clusters don't really count as "non-spherical"), then the answer would be filamentary structures (both the most massive, and the largest in scale). Here's an image from the Millennium Simulation to show what a super cluster would look like:

![enter image description here](https://i.sstatic.net/JdmmE.jpg)


---

### Answer by username_10 on 2013-11-15. Score: 5

If you count conglomerates of galaxy style objects, the largest structure in the universe so far is the [Huge Large Quasar Group](http://en.wikipedia.org/wiki/Huge-LQG).

It seems to be four billion ly in size, and contains dozens of Quasars, which in turn are very active galactic nuclei.

![enter image description here](https://i.sstatic.net/DJv9R.png)


---

### Answer by username_11 on 2013-12-17. Score: 3

Let me see, some objects are listed because of their records. First, nebulae, which are huge clouds of dust and gas. The largest in the Milky Way's neighborhood is the Tarantula Nebula (30 Doradus, NGC 2070 or Caldwell 103).:

![Tarantula Nebula](https://2.bp.blogspot.com/_viputHRpZ2A/SRL1YHQxmKI/AAAAAAAABSY/IQN4-D4FClY/s400/NGC+2070+by+Joe+Brimacombe.jpg)

This is the largest nebula in the Milky Way's neighborhood, at 300 light-years (almost 100 pc). But if we are in the universal record, that would be NGC 604, which is 740 light-years (240 pc) across.:

[![NGC 604](https://i.sstatic.net/RdfBm.jpg)](https://i.sstatic.net/RdfBm.jpg)  
(source: [wolaver.org](http://www.wolaver.org/Space/ngc604.jpg))

Next, galaxies, which come in different shapes. Spirals first, and what like called2voyage has said, is NGC 262. Because he can't provide a pic, I will!:

[![NGC 262](https://i.sstatic.net/msj9f.jpg)](https://i.sstatic.net/msj9f.jpg)  
(source: [cseligman.com](http://cseligman.com/text/atlas/ngc262.jpg))

NGC 262 is a giant Seyfert spiral, and is 1.3 million light-years across, more than two times larger than the mistakenly clamed largest spiral last January 2013, NGC 6872.:

![NGC 6872](https://www.nasa.gov/sites/default/files/images/718359main_composite_no_labels.jpg)

I don't know why they claimed this one as largest, at 522,000 light-years across *only* is less than half as that of NGC 262.

But the hands-down king of all galaxies is IC 1101, at 5.6 million light-years across, and is the record holder since 1989.:

![IC 1101](https://4.bp.blogspot.com/-kFoYO-Y4AW4/T3_zoxObL8I/AAAAAAAAfH8/02vUYCn5q44/s400/ic_1101.jpg)

A size comparison of this monster:

[![IC 1101 vs. Milky Way and other galaxies](https://i.sstatic.net/hVh0B.jpg)](https://i.sstatic.net/hVh0B.jpg)  
(source: [areavoices.com](https://astrobob.areavoices.com/files/2013/07/IC-1101-compared-to-Milky-Way1-1024x563.jpg))

Next, structures. aneroid has the right answer. It's name is Hercules-Corona Borealis Great Wall, some 10 billion light-years across.

> **Comments:**
> **username_12**: Good answer, but are you sure the last graphic is correct? The Milky Way and Andromeda are much closer in size.  

---

### Answer by username_13 on 2014-01-09. Score: 2

All these answers are, of course, correct. I only want to make a simple observation. According to the definition linked in the OP, an *astronomical object* is gravitationally bound. So we are looking for the largest gravitationally bound object.

If the universe were closed, it's bound and hence the largest astronomical object ;-)

However, it appears the universe is expanding forever and hence not bound. The largest bound objects are galaxy clusters and galaxy super clusters. These objects have just formed or are still forming: the dynamical (orbital) time scale at their outskirts is comparable to the age of the universe.

Thus, the largest bound objects will be larger if you wait a few giga years ...


---

### Answer by username_6 on 2019-06-06. Score: 0

The largest "complex, less cohesively bound structure, which may consist of multiple bodies or even other objects with substructures" known object is the [Shapley Supercluster](https://en.wikipedia.org/wiki/Shapley_Supercluster), which comprises 76000 galaxies. It is supossed that [Laniakea](https://es.wikipedia.org/wiki/Laniakea) (our own supercluster) moves towards it and both may be part of a bigger structure, yet to be confirmed.


---

### Answer by username_15 on 2014-12-12. Score: 0

Warning: citations above about IC 1101 being the largest known galaxy are probably wrong! Wikipedia's claimed 5 Mly size is certainly incorrect.

The visible light extent is about 360 kly ([NED's summary page](http://ned.ipac.caltech.edu/cgi-bin/objsearch?objname=IC%201101&extend=no&hconst=73&omegam=0.27&omegav=0.73&corr_z=1&out_csys=Equatorial&out_equinox=J2000.0&obj_sort=RA%20or%20Longitude&of=pre_text&zv_breaker=30000.0&list_limit=5&img_stamp=YES#ObjNo1) gives a major diameter of 1.2' and a redshift of z=0.077947, for a physical size of around 115 kpc, or 370 kly). The largest measurement one could reasonably suggest for IC 1101 (around 500 kpc, or 1.5 Mly) comes from the maximal measured extent of the diffuse light from Uson, Bough & Kuhn (1991). That's not what one usually thinks of when talking about the "size" of a galaxy. Usually we refer to the radius in which most of the visible light is enclosed, not the maximum distance we could possibly measure light that might be associated with the galaxy.

Similarly, NGC 262 is not 1.3 Mly across. It has an extended cold Hydrogen gas halo of around 600 kly (~10' HI measurement from Morris & Wannier 1979, distance ~65 Mpc), but the physical extent of its stars is around 66 kly: large for a spiral, but not huge.

To answer the question: I'd go with galaxy superclusters as being the largest currently gravitationally-bound objects in the universe.


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### Answer by username_14 on 2016-06-11. Score: -2

Well, this is my relatively inaccurate size comparison of galaxies. IC 1101 is 6 million LY at this scale, NGC 263 is 2.3 million LY, and there are some other galaxies.

[![](https://i.sstatic.net/Vf8JK.png)](https://i.sstatic.net/Vf8JK.png)


---

