As far as I know, scientists have been able to see a lot of differently shaped galaxies in our visible universe through modern age telescopes. But I was wondering how it was possible to know how our own galaxy looks like without going out of it to see its shape?
Answer
We obviously do not know the shape exactly, but by measuring the positions of visible stars in our neighborhood We can tell that it is a spiral arm galaxy. In fact to the naked eye, the fact that we see a band of diffuse light called the Milky Way shows that we are in a flat type of galaxy and not in a globular cluster or an elliptical galaxy. There is a lot of evidence that the supermassive black hole that is at the center of our galaxy is located in Sagittarius A and we know the distance to that black hole. In addition we can measure the orbital velocity of stars rotating around the galaxy.
However, we can only see individual stars that are somewhat close to our position about 2/3 of the way out from the center of our galaxy - there is too much obscuring dust to see to the other side of the galaxy, for example. So we will always be somewhat limited in our ability to map out our galaxy exactly. However we do know enough to confidently say that we are in a spiral armed type of galaxy.
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