What is a galaxy made of and what are the different types?

Answer 1

Galaxies are made up of stars, typically in orbit around a central black hole. Our milky way has something around 200 or 300 billion stars. Galaxies also contain stellar remnants like white dwarfs, neutron stars, and stellar mass black holes; nebulae of gas and dust, and a very sparse interstellar medium containing small amounts of particles. Because of observations of anomalies in rotational velocities, galaxies are also assumed to contain significant amounts of non-visible or dark matter.

The stars themselves are made up mostly of lighter elements like hydrogen and helium, and heavier elements decreasing in fraction of the composition as the atomic number increases.

Galactic types are classified by their appearance, which falls into three main types, irregular, elliptical, and spiral. Spirals subdivide into barred and non-barred, although some evidence indicates bars may be temporary structures. The Hubble classification scheme assigns a short letter designation to the various types. Our own Milky Way is a barred spiral galaxy.

Answer 2

A galaxy is made up of stars, planets, gas, dust, and dark matter. There are three main types of galaxies: spiral galaxies with arms that spiral out from a central core like the Milky Way, elliptical galaxies that are round or oval-shaped, and irregular galaxies that have unusual shapes and structures.