# Our knowledge of other galaxies **URL:** \ **Category:** Factual Questions\ **Created:** [April 2, 2009, 12:56am UTC](https://boards.straightdope.com/t/our-knowledge-of-other-galaxies/491661 "2009-04-02T00:56:41Z")\ **Posts on this page:** 10\ **Page:** 1
**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:** [April 2, 2009, 12:56am UTC](https://boards.straightdope.com/t/our-knowledge-of-other-galaxies/491661/1 "2009-04-02T00:56:41Z")
When I was a kid in the 50s, I remember studying astronomy in 3rd grade (age about 8). We learned about the solar system, constellations, the Milky Way, Andromeda, and i think the Magellanic Clouds. My mother, born in 1913, remembered studying the solar system and the Milky Way, and that’s it. So I’m wondering: when did scientists first realize that the Milky Way was not the only galaxy? Was there a specific telescope that was the first one strong enough to show that Andromeda wasn’t just another star? And was this a totally “WTF?” discovery, or had scientists already suspected it to be the case? ---
**Author:** ![Fubaya](https://avatars.discourse-cdn.com/v4/letter/f/c2a13f/32.png) [@Fubaya](https://boards.straightdope.com/u/Fubaya)\ **Post date:** [April 2, 2009, 1:48am UTC](https://boards.straightdope.com/t/our-knowledge-of-other-galaxies/491661/2 "2009-04-02T01:48:19Z")
[Hubble](http://en.wikipedia.org/wiki/Edwin_Hubble#The_Universe_goes_beyond_the_Milky_Way_galaxy) proved it in 1925, but the idea had been around a couple hundred years [before](http://en.wikipedia.org/wiki/Galaxy#Observation_history) him, just waiting for technology to become good enough to prove it. ---
**Author:** ![billfish678](https://avatars.discourse-cdn.com/v4/letter/b/7bcc69/32.png) [@billfish678](https://boards.straightdope.com/u/billfish678)\ **Post date:** [April 2, 2009, 1:54am UTC](https://boards.straightdope.com/t/our-knowledge-of-other-galaxies/491661/3 "2009-04-02T01:54:49Z")
Hi Busy, dont have time to check references…but off the top of my head “we” knew what galaxies were sometime between the 20’s and ww2. I am not sure whether it was a eureka moment, or a slow “ahhhhhhh” kind of revelation that took years to confirm and accept. Do an internet search for “hubble” (the astronomer, not the the telescope) and “galaxies”…that should give you a good starting point I’ve always thought “man, THATS when the universe got BIG” As a thought experiment, ponder this. You look at the sky. There is the sun, big and bright. You have some idea of how far way it is (pretty damn far) Then there are all these stars. Hmmm, they must be like fireflys or sumptin. Then, one day, you figure out stars are just like the sun. Holy crap, just HOW far away do those suckers have to be for them to look like that? Same thing with the galaxy revelation, only unbelievably bigger! ---
**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:** [April 2, 2009, 4:28am UTC](https://boards.straightdope.com/t/our-knowledge-of-other-galaxies/491661/4 "2009-04-02T04:28:57Z")
> [@billfish678](#): > > Then, one day, you figure out stars are just like the sun. Holy crap, just HOW far away do those suckers have to be for them to look like that? Not only that, but some of them are gigantic, compared to our puny sun. ---
**Author:** ![Wendell\_Wagner](https://avatars.discourse-cdn.com/v4/letter/w/8491ac/32.png) [@Wendell\_Wagner](https://boards.straightdope.com/u/Wendell_Wagner)\ **Post date:** [April 2, 2009, 12:14pm UTC](https://boards.straightdope.com/t/our-knowledge-of-other-galaxies/491661/5 "2009-04-02T12:14:08Z")
panache45 writes: \> Was there a specific telescope that was the first one strong enough to show \> that Andromeda wasn’t just another star? The Andromeda Galaxy is seven times as wide in apparent diameter as the Moon is as viewed from Earth. Nobody ever thought it was a star: > **[Andromeda Galaxy](https://en.wikipedia.org/wiki/Andromeda_Galaxy)** > > The Andromeda Galaxy is a barred spiral galaxy and is the nearest major galaxy to the Milky Way. It was originally named the Andromeda Nebula and is cataloged as Messier 31, M31, and NGC 224. Andromeda has a diameter of about 46.56 kiloparsecs (152,000 light-years) and is approximately 765 kpc (2.5 million light-years) from Earth. The galaxy's name stems from the area of Earth's sky in which it appears, the constellation of Andromeda, which itself is named after the princess who was the wife o It was considered to be a cluster of stars it was found to be a separate galaxy. ---
**Author:** ![Hari\_Seldon](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/hari_seldon/32/5173_2.png) [@Hari\_Seldon](https://boards.straightdope.com/u/Hari_Seldon)\ **Post date:** [April 2, 2009, 12:16pm UTC](https://boards.straightdope.com/t/our-knowledge-of-other-galaxies/491661/6 "2009-04-02T12:16:38Z")
Actually Andromeda was known not to be a star. In 1781 Charles Messier published his catalog of nebulas, see [http://www.delphes.net/messier/xtra/history/mcathist.html](http://www.delphes.net/messier/xtra/history/mcathist.html). Andromeda was M31. That and the galaxy in the triangle (M33) were the only naked eye visible ones, the latter only barely, but telescopically, they were all diffuse “clouds”. I don’t know that Messier had any idea what they were and most were either large hydrogen clouds or globular clusters in our galaxy, but at least those two as well as the Magellanic clouds were galaxies. The latter were two small satelite galaxies to the Milky Way. ---
**Author:** ![Alive\_At\_Both\_Ends](https://avatars.discourse-cdn.com/v4/letter/a/73ab20/32.png) [@Alive\_At\_Both\_Ends](https://boards.straightdope.com/u/Alive_At_Both_Ends)\ **Post date:** [April 2, 2009, 1:34pm UTC](https://boards.straightdope.com/t/our-knowledge-of-other-galaxies/491661/7 "2009-04-02T13:34:09Z")
> [@Hari\_Seldon](#): > > Andromeda was M31. That and the galaxy in the triangle (M33) were the only naked eye visible ones, the latter only barely, but telescopically, they were all diffuse “clouds”. I don’t know that Messier had any idea what they were… They weren’t all diffuse clouds. Some of them were known by Messier to be star clusters, one obvious example being M45 (the Pleiades), which is also naked-eye visible of course. ---
**Author:** ![Wendell\_Wagner](https://avatars.discourse-cdn.com/v4/letter/w/8491ac/32.png) [@Wendell\_Wagner](https://boards.straightdope.com/u/Wendell_Wagner)\ **Post date:** [April 2, 2009, 1:39pm UTC](https://boards.straightdope.com/t/our-knowledge-of-other-galaxies/491661/8 "2009-04-02T13:39:50Z")
Excuse me, I should have written: \> It was considered to be a cluster of stars before it was found to be a separate \> galaxy. ---
**Author:** ![Alive\_At\_Both\_Ends](https://avatars.discourse-cdn.com/v4/letter/a/73ab20/32.png) [@Alive\_At\_Both\_Ends](https://boards.straightdope.com/u/Alive_At_Both_Ends)\ **Post date:** [April 2, 2009, 1:43pm UTC](https://boards.straightdope.com/t/our-knowledge-of-other-galaxies/491661/9 "2009-04-02T13:43:28Z")
> [@Wendell\_Wagner](#): > > Excuse me, I should have written: > > \> It was considered to be a cluster of stars before it was found to be a separate > \> galaxy. Well, in a larger sense, a galaxy \*is \*a cluster of stars.😉 ---
**Author:** ![Freddy\_the\_Pig](https://avatars.discourse-cdn.com/v4/letter/f/a587f6/32.png) [@Freddy\_the\_Pig](https://boards.straightdope.com/u/Freddy_the_Pig)\ **Post date:** [April 2, 2009, 1:58pm UTC](https://boards.straightdope.com/t/our-knowledge-of-other-galaxies/491661/10 "2009-04-02T13:58:39Z")
The Andromeda Galaxy looks like, and for a long time was considered to be, a nebula–that is, a diffuse gas cloud. It was even called the Andromeda Nebula. In the late Nineteenth Century, astronomers began taking spectra, and discovered the spectrum looked more like that of a star or star cluster. This led to a period of confusion during which no one was sure what it was. Hubble finally settled the matter by proving that it was in fact a very large and very distant star cluster, so large and distant that it was comparable to the Milky Way and would henceforth be described as a “galaxy”.