Question

Create and present a hypothesis of why you believe the Milky Way looks the way it does. Formulate a method to test this to create a theory. Whose theory (if any) supports this concept and description?  Formulate and present your own theory of why you believe the galaxy looks the way it does. Be sure to provide support for your theory.

Answer 1

Take a look at the picture below to get your first clue about the Milky Way's shape:

This image was taken with the Kuiper Airborne Observatory in the direction of the constellation Sagittarius. I can't post the most common view that you get of the Milky Way because that kind of picture, taken by a simple camera pointed up at the sky, is usually copyrighted.

Recently, astronomers using the 2MASS infrared sky survey imaged the entire sky, and put together this dramatic image of the complete Milky Way:

It is very clear from these images, and a bit of detective work, that the Milky Way is a flat system of stars, with a central bulge located in the constellation Sagittarius. So, we know the Milky Way is a very flat system in 3-dimensions, because from the inside, its projection on the sky is a very narrow band of faint stars. We also know it does not have a gigantic nucleus because when we look along the Milky Way on the sky, we do not see a 'ball' of light peeking up from the Milky Way. Using our knowledge of the shapes of other galaxies, we easily conclude it must be a version of a spiral-type galaxy with an unremarkable central nucleus. Here is a similar type of galaxy seen edge-on:

This is the galaxy NGC 4565 taken by Dr. Crowe and his summer students at the University of Hawaii. Note, the Milky Way image was taken from INSIDE our galaxy. We cannot travel outside our galaxy to see what it really looks like because the distance (over 100,000 light years) is too far to travel.