Galaxies
Galaxies are a huge collection of stars, planets, nebulae, gas, dust, and empty space in an orbit of the nucleus or a possible black hole. Galaxies are huge regions of space filling most of the detectable matter in the universe and approximately 50 billion galaxies exist.
There are four types of galaxies: spiral, barred spiral, elliptical, and irregular galaxies.
Spiral: A spiral galaxy orbits the center of the galaxy (which is presumably a giant black hole or possibly a cluster of stars causing a greater gravitational force). Due to this central gravity, the galaxy has a spiral look and arms spiraling out like a pinwheel.
Barred Spiral: A Barred spiral has a bar of stars across the center and the spiral arms are at the end of the bars other than that they are identical to their cousin, the spiral galaxy.
Elliptical: Elliptical galaxies have a spherical or elliptic shape, and maintain this shape as they move through space. They contain groups of old stars, and little bits of gas and dust. Some elliptical galaxies resemble nebula, or large clouds of gas, because they are so old.
Irregulars: These belong in no group since they seem to be unlike any other. These galaxies either become or start out as irregulars and my change due to age or collision with another
galaxy.
