•Bright
objects visible at large distances
•Objects
above or below the plane – so not as obscured
•
•Ways
to measure distances to those objects
•Ways
to see material other than stars
–Gas,
dust, ???, mass distribution
•Ways
to map motion of objects in our Galaxy
–
•Examples
of other Galaxies
–The
Shapley-Curtis debate:
•Are
spiral nebulae external galaxies or a type of object within our own galaxy