Astronomy: Milky Way

Buldge (of a spiral galaxy)

Older ages (yellow/red in color)

Lower abundances of heavy elements

Orbit spherically, close to the center of the galaxy

Disk (of a galaxy)

orbit galactic center in roughly circular paths that all go in same direction in same plane.

Buldge (of a spiral galaxy)

Older ages (yellow/red in color)

Lower abundances of heavy elements

Orbit spherically, close to the center of the galaxy

Disk (of a galaxy)

orbit galactic center in roughly circular paths that all go in same direction in same plane.

Disk population

Large age range (younger/bluer in the spiral arms)

Higher abundances of heavy elements

Orbits mostly confined to the disk

galactic fountain

halo (of a galaxy)

orbit center of galaxy but orientation of paths relatively random

halo population

Oldest ages (yellow/red in color)

Lowest abundances of heavy elements

Found in dense globular clusters with high orbital velocities

Orbit spherically at large distances from the galactic center

ionization nebula

protogalactic cloud

spiral arms

part of a fairly flat disk of stars with a bright central bulge

star-gas-star cycle

spiral density waves