How can we know the shape of the milkyway Galaxy precisely?

Question

As of assuming two very close planets to be one

In: 11

Answer 1

We don’t really know it precisely.

We do know the shapes of other galaxies and have figured which type of galaxy ours is and what it likely looks like.

We have some idea about spiral arms and bar in the center, but it is really difficult to get a precise idea what exactly it would look like from outside, when we can only see it from the inside a large parts of it are behind other parts.

Planets are not really involved in this.