What is the composition of the Milky Way Galaxy?

Answer 1

Spiral galaxies tend to have concentrations of heavier elements. This is because the spiral arms are "density waves" that sweep through the galaxy, disturbing gaseous nebula and fostering active star formation. As stars age, they create heavier elements (anything more complex than hydrogen and helium) and as the die they spread them around, to be used in the next generation.

Elliptical galaxies have star formation, but not nearly as active as spiral galaxies. As such they have much more basic compositions, almost entirely hydrogen and helium.

Answer 2

About 80% of the Milky Way's mass is in dark matter. The details are unknown. The remainder is in stars, star corpses (white dwarves, neutron stars, black holes), planets, asteroids, comets, dust, gas, and a few other objects.

Answer 3

The Milky Way Galaxy is composed of stars, planets, gas, dust, and dark matter. It consists of a central bulge, a disk with spiral arms, and a halo of old stars and globular clusters. The exact composition and structure of the Milky Way are still being studied by astronomers.