In article , Odysseus
wrote:

Bill Duncan wrote:

When I included our galaxy,I was using all of the artists' concepts
showing what our galaxy might look like if viewed from above and where
we are located in it.I know we see it from the edge.I also know our
galaxy is considered to be a spiral one.So can you tell me how an
astronomer can determine the shape of our own galaxy froom an edge on
view.Thanks,Bill.

Mainly by mapping stars. Different kinds of objects occur in
different distributions in space, allowing astronomers to trace out
various features of the galaxy. The spiral arms are characterized by
young "Population I" stars, galactic star clusters, and diffuse
nebulae (bright and dark), so when these objects are plotted --
somewhat tricky because the distances to most of them can only be
estimated -- the positions of the arms, at least in our quadrant of
the galaxy, can be mapped out. The centre of the galaxy is obstructed
from our view, but instruments capable of imaging radio and infrared
frequencies that pass through the intervening dust and gas can
provide a picture of the hub.

See http://www.anzwers.org/free/universe/5000lys.html.

I want to thank everyone for their input.Bill.