eli5 How do we know what other milky ways look like?


So I’ve been watching a lot of video’s about how small we are compared to the universe. ( like [this](https://www.youtube.com/watch?v=9rrG5Nppaew&ab_channel=DANIELKAMARUZAMAN) ). And I don’t understand one thing. How do we know what our milky way looks like? And how do we know what the other millky ways look like?

In: Earth Science

“The Milky Way” is the name we give our galaxy. Other galaxies are not called “milky ways”. Just “other galaxies”.

We can discern the shape of our galaxy by plotting the distance and location of all the stars we can see within our area, and that gives us a good idea of what the shape is. Like looking around at the houses in your neighborhood and then drawing an aerial map from that information. It’s probably not perfect but gets us a good idea to work from.

And we know what other galaxies look like because we just look at them.

If you spill milk it looks like a circle from the top.

But if you look at it from the side of the table, it looks long like a line.

Same thing with our galaxy. We see all the other stars near the middle as a bright line in the sky. And stars are more clumped together in the center or our galaxy, like milk chunks.

Galaxies we can take pictures of in the night sky. You can’t always pick them out with the human eye but with powerful telescope settings it’s not an issue to get clear photos of their shapes.

Most galaxies fall into a handful of simple types and shapes. For our galaxy, the Milky Way, we can’t see the whole galaxy from the outside, but we can observe how all of the stars around us behave and piece together which of the common shapes our galaxy would have to be.

I assume by milky way you mean our galaxy.

The answer is really really good (and expensive) telescopes in observatories plus space telescopes.

There are 4 types of galaxies based on shape: spiral, elliptical, lenticular, and irregular. The Milky Way galaxy (ours) is spiral. Andromeda is also spiral. Cygnus A is elliptical, if I remember right.

That help?

Every picture you see of our own galaxy from the outside, like a top down view is at least partly an artist’s rendition

We can tell for the most part where most stars at though just from where they are in the sky. Earth also happens to be pretty close to the outside edge so most of the galaxy is visible as well.

Some parts though like stars of the far side, esp those directly opposite the galactic core we can’t see at all cause of the stuff in the way.

So computer analysis gives you most of it, and we fill in the gaps by assuming out galaxy is more or less symmetrical.

Other galaxies we can just look at to get the general shape of, though similarly, anything that looks too detailed is likely an artististic representation.