# How big would the Andromeda galaxy be if we could see it all? **URL:** \ **Category:** Factual Questions\ **Created:** [August 26, 2009, 2:21pm UTC](https://boards.straightdope.com/t/how-big-would-the-andromeda-galaxy-be-if-we-could-see-it-all/507765 "2009-08-26T14:21:23Z")\ **Posts on this page:** 20\ **Page:** 1
**Author:** ![CC](https://avatars.discourse-cdn.com/v4/letter/c/f1d935/32.png) [@CC](https://boards.straightdope.com/u/CC)\ **Post date:** [August 26, 2009, 2:21pm UTC](https://boards.straightdope.com/t/how-big-would-the-andromeda-galaxy-be-if-we-could-see-it-all/507765/1 "2009-08-26T14:21:23Z")
I’ll try this again, as the answers in a previous thread (that I can’t find) don’t satisfy. If we could see the entire galaxy with the naked eye, would it, in fact, occupy a space in our sky the width of 7 moons? ---
**Author:** ![Grey](https://avatars.discourse-cdn.com/v4/letter/g/b782af/32.png) [@Grey](https://boards.straightdope.com/u/Grey)\ **Post date:** [August 26, 2009, 2:49pm UTC](https://boards.straightdope.com/t/how-big-would-the-andromeda-galaxy-be-if-we-could-see-it-all/507765/2 "2009-08-26T14:49:27Z")
Well you can see the central bulge with the naked eye, but the galaxy proper extends about 6 full moon widths (180 arcminutes) ---
**Author:** ![jayjay](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/jayjay/32/6765_2.png) [@jayjay](https://boards.straightdope.com/u/jayjay)\ **Post date:** [August 26, 2009, 2:50pm UTC](https://boards.straightdope.com/t/how-big-would-the-andromeda-galaxy-be-if-we-could-see-it-all/507765/3 "2009-08-26T14:50:09Z")
[Astronomy Picture of the Day](http://antwrp.gsfc.nasa.gov/apod/ap061228.html) took this one on a while ago. ---
**Author:** ![Floppy\_Joe](https://avatars.discourse-cdn.com/v4/letter/f/3bc359/32.png) [@Floppy\_Joe](https://boards.straightdope.com/u/Floppy_Joe)\ **Post date:** [August 26, 2009, 3:02pm UTC](https://boards.straightdope.com/t/how-big-would-the-andromeda-galaxy-be-if-we-could-see-it-all/507765/4 "2009-08-26T15:02:31Z")
Now **THAT** was illuminating! ---
**Author:** ![CC](https://avatars.discourse-cdn.com/v4/letter/c/f1d935/32.png) [@CC](https://boards.straightdope.com/u/CC)\ **Post date:** [August 26, 2009, 4:00pm UTC](https://boards.straightdope.com/t/how-big-would-the-andromeda-galaxy-be-if-we-could-see-it-all/507765/5 "2009-08-26T16:00:54Z")
Ok. I believe. This is such a mind-fuck! It’s up there in the sky. That big. And that far away. Boggled, I am. ---
**Author:** ![pravnik](https://avatars.discourse-cdn.com/v4/letter/p/8edcca/32.png) [@pravnik](https://boards.straightdope.com/u/pravnik)\ **Post date:** [August 26, 2009, 4:09pm UTC](https://boards.straightdope.com/t/how-big-would-the-andromeda-galaxy-be-if-we-could-see-it-all/507765/6 "2009-08-26T16:09:42Z")
I ran across another mind blower like that recently in a star guide - an object that, if it was as close to the Earth as the Orion nebula is, would be sixty times the apparent size of the Sun. I can’t remember what it was offhand, though. ---
**Author:** ![Polycarp](https://avatars.discourse-cdn.com/v4/letter/p/82dd89/32.png) [@Polycarp](https://boards.straightdope.com/u/Polycarp)\ **Post date:** [August 26, 2009, 4:12pm UTC](https://boards.straightdope.com/t/how-big-would-the-andromeda-galaxy-be-if-we-could-see-it-all/507765/7 "2009-08-26T16:12:05Z")
As I remember, we are able to see only three or four galaxies (besides the Milky Way) with the naked eye: the two Magellanic Clouds. M-31, and at the very edge of vision for those with perfect eyesight in times of perfect seeing, M-33 in Triangulum. The latter two show up only as faint blobs (their cores) to the naked eye. ---
**Author:** ![pravnik](https://avatars.discourse-cdn.com/v4/letter/p/8edcca/32.png) [@pravnik](https://boards.straightdope.com/u/pravnik)\ **Post date:** [August 26, 2009, 4:20pm UTC](https://boards.straightdope.com/t/how-big-would-the-andromeda-galaxy-be-if-we-could-see-it-all/507765/8 "2009-08-26T16:20:51Z")
> [@pravnik](#): > > I ran across another mind blower like that recently in a star guide - an object that, if it was as close to the Earth as the Orion nebula is, would be sixty times the apparent size of the Sun. I can’t remember what it was offhand, though. I think I remember - it was the [Tarantula Nebula](http://en.wikipedia.org/wiki/Tarantula_Nebula). Polycarp’s mention of the Large Magellanic Cloud reminded me. ---
**Author:** ![Polycarp](https://avatars.discourse-cdn.com/v4/letter/p/82dd89/32.png) [@Polycarp](https://boards.straightdope.com/u/Polycarp)\ **Post date:** [August 26, 2009, 5:13pm UTC](https://boards.straightdope.com/t/how-big-would-the-andromeda-galaxy-be-if-we-could-see-it-all/507765/9 "2009-08-26T17:13:57Z")
Also of interest is the [Gum Nebula](http://antwrp.gsfc.nasa.gov/apod/ap060519.html) – notice the dimensions mentioned. This is a supernova remnant of which the near edge isvless than 100 light years, covering a large part of the Southern sky – the image is **41 degrees wide** , but is so dim that it is invisible to the naked eye. ---
**Author:** ![Duckster](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/duckster/32/1244_2.png) [@Duckster](https://boards.straightdope.com/u/Duckster)\ **Post date:** [August 26, 2009, 5:28pm UTC](https://boards.straightdope.com/t/how-big-would-the-andromeda-galaxy-be-if-we-could-see-it-all/507765/10 "2009-08-26T17:28:18Z")
The difficulty is clearly seeing the Andromeda galaxy with the naked eye is better known as the Andromeda Strain. ---
**Author:** ![CC](https://avatars.discourse-cdn.com/v4/letter/c/f1d935/32.png) [@CC](https://boards.straightdope.com/u/CC)\ **Post date:** [August 26, 2009, 5:46pm UTC](https://boards.straightdope.com/t/how-big-would-the-andromeda-galaxy-be-if-we-could-see-it-all/507765/11 "2009-08-26T17:46:45Z")
This is so fascinating. It’s almost the reverse of what mind-numbing knowledge of the size of the universe first did to people who had thought that what you could see was pretty much within a distant reach. And then, they suddenly had to reckon with the idea that the universe was almost infinitely large. I’ve just had it go from “everything’s so far away that \*everything \*except the things in the solar system look like a dot,” to “this thing that’s gazzilions of miles away still looks this big to us.” ---
**Author:** ![Gorsnak](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/gorsnak/32/7587_2.png) [@Gorsnak](https://boards.straightdope.com/u/Gorsnak)\ **Post date:** [August 26, 2009, 6:37pm UTC](https://boards.straightdope.com/t/how-big-would-the-andromeda-galaxy-be-if-we-could-see-it-all/507765/12 "2009-08-26T18:37:52Z")
What gets me is how freaking _huge_ it has to be to cover that sort of angle at 2 million lightyears distance. ---
**Author:** ![BlinkingDuck](https://avatars.discourse-cdn.com/v4/letter/b/eada6e/32.png) [@BlinkingDuck](https://boards.straightdope.com/u/BlinkingDuck)\ **Post date:** [August 26, 2009, 6:39pm UTC](https://boards.straightdope.com/t/how-big-would-the-andromeda-galaxy-be-if-we-could-see-it-all/507765/13 "2009-08-26T18:39:33Z")
> [@jayjay](#): > > [Astronomy Picture of the Day](http://antwrp.gsfc.nasa.gov/apod/ap061228.html) took this one on a while ago. WOW! I had no idea the Andromeda galaxy was between the Earth and the moon! Ignorance fought. ---
**Author:** ![jayjay](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/jayjay/32/6765_2.png) [@jayjay](https://boards.straightdope.com/u/jayjay)\ **Post date:** [August 26, 2009, 6:50pm UTC](https://boards.straightdope.com/t/how-big-would-the-andromeda-galaxy-be-if-we-could-see-it-all/507765/14 "2009-08-26T18:50:49Z")
> [@BlinkingDuck](#): > > WOW! I had no idea the Andromeda galaxy was between the Earth and the moon! > > Ignorance fought. Am I being whooshed? 😕 ---
**Author:** ![Triskadecamus](https://avatars.discourse-cdn.com/v4/letter/t/b19c9b/32.png) [@Triskadecamus](https://boards.straightdope.com/u/Triskadecamus)\ **Post date:** [August 26, 2009, 6:54pm UTC](https://boards.straightdope.com/t/how-big-would-the-andromeda-galaxy-be-if-we-could-see-it-all/507765/15 "2009-08-26T18:54:30Z")
I recommend making APOD your home page: [Astronomy Picture of the Day](http://antwrp.gsfc.nasa.gov/apod/astropix.html) It changes every day, and it is almost always worth the look. Click on the picture for a bigger version, and in Mozilla, click it again for full size. Awesome. Tris ---
**Author:** ![cmyk](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/cmyk/32/3353_2.png) [@cmyk](https://boards.straightdope.com/u/cmyk)\ **Post date:** [August 26, 2009, 7:12pm UTC](https://boards.straightdope.com/t/how-big-would-the-andromeda-galaxy-be-if-we-could-see-it-all/507765/16 "2009-08-26T19:12:05Z")
Shit. People don’t even know which one are the planets (which are painfully obvious to me, except Uranus and Neptune). But yes, there are all sorts of HUGE things in the sky, that if they weren’t so dim, would fill the sky with dazzling beauty. One thing to consider, is the biggest galaxy we can see with the naked eye is, of course, our own Milky Way galaxy. Think about how relatively close the Milky Way is to us (we are looking toward the center, edge on, with the center being ~33,000 LY away), than the Andromeda galaxy (about 2.5 million LY away), and _still_ how dim the Milky Way is to our naked eye. ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [August 26, 2009, 7:48pm UTC](https://boards.straightdope.com/t/how-big-would-the-andromeda-galaxy-be-if-we-could-see-it-all/507765/17 "2009-08-26T19:48:58Z")
> [@](#): > > One thing to consider, is the biggest galaxy we can see with the naked eye is, of course, our own Milky Way galaxy. Only if by “biggest”, you mean in angular size. The Milky Way is in fact a bit on the large side for spiral galaxies, but M31 is a bit bigger yet. ---
**Author:** ![cmyk](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/cmyk/32/3353_2.png) [@cmyk](https://boards.straightdope.com/u/cmyk)\ **Post date:** [August 26, 2009, 7:56pm UTC](https://boards.straightdope.com/t/how-big-would-the-andromeda-galaxy-be-if-we-could-see-it-all/507765/18 "2009-08-26T19:56:10Z")
> [@Chronos](#): > > Only if by “biggest”, you mean in angular size. The Milky Way is in fact a bit on the large side for spiral galaxies, but M31 is a bit bigger yet. But of course! 😉 ---
**Author:** ![Munch](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/munch/32/5281_2.png) [@Munch](https://boards.straightdope.com/u/Munch)\ **Post date:** [August 26, 2009, 8:11pm UTC](https://boards.straightdope.com/t/how-big-would-the-andromeda-galaxy-be-if-we-could-see-it-all/507765/19 "2009-08-26T20:11:12Z")
Here’s another interesting “if only we could see it\* with the naked eye” picture: > **[APOD: 2009 April 11 - The Big Picture](https://apod.nasa.gov/apod/ap090411.html)** > > A different astronomy and space science > related image is featured each day, along with a brief explanation. \*“It”, in this case, not being Andromeda, but rather other celestial objects. ---
**Author:** ![panache45](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/panache45/32/64_2.png) [@panache45](https://boards.straightdope.com/u/panache45)\ **Post date:** [August 26, 2009, 8:47pm UTC](https://boards.straightdope.com/t/how-big-would-the-andromeda-galaxy-be-if-we-could-see-it-all/507765/20 "2009-08-26T20:47:15Z")
> [@BlinkingDuck](#): > > WOW! I had no idea the Andromeda galaxy was between the Earth and the moon! Yes, and astronauts on the moon were able to see the [back](http://s174.photobucket.com/albums/w113/flamingriver/?action=view¤t=fromthemoon.jpg) of it.