how do we know thaat our galaxy is spiral?

Question

we have to come outside from our galaxy to see of what shape it is but that is not possible so how do we know that it is spiral one ?

Answer 1

The most direct evidence that the Milky Way is a spiral is from radio telescope surveys of atomic and molecular gas. The data in these surveys is 3-dimensional, since they not only give the brightness at each point in the sky, but they also give the brightness at each velocity at each point in the sky. In these 3-dimensional "data cubes", the spiral arms are readily apparent in a way which is consistent with the theory of spiral structure and with similar observations of other galaxies that are nearly edge-on.

Answer 2

Actually, in 2005 it was disovered that the Milky Way is not a regular spiral galaxy, but is what is known as a Barred Spiral galaxy. The difference is a "regular" spiral galaxy has numerous "arms" spreading out from the centre. A barred spiral galaxy only has two.

This discovery was made by the Spitzer Space telescope using infrared images.

When scientists looked at the center, or bulge, of our galaxy, they observed that it was not circular, but almost oval or peanut-shaped. After observing other barred spiral galaxies in which they could clearly see that their bulges were peanut-shaped, the obvious conclusion was drawn.

Answer 3

we do not have to come from the outside to determine it's shape. we realized that earth is round long before going into space... calculations and photos taken by telescopes tell us galaxies are spiraled...

Answer 4

It's done by measuring the densities and distances to stars. By knowing how far away stars are and how many are that far and in what direction, we can draw a picture as if we were looking down on the galaxy from above..

Answer 5

We know this from lengthy observation of the Stars.