Galaxies...
What is a Galaxy?
A galaxy is a large area of stars, gas, and dust, containing BILLIONS of stars. The galaxies were classified with the luminous gas, clouds, or bright nebulae within the Milky Way. Harlow Shapley encouraged exclusive use of the term, "galaxies". There are BILLIONS of galaxies. There are spiral galaxies, elliptical galaxies, and irregular galaxies. The Milky Way is OUR galaxy. It is a spiral galaxy. A typical spiral galaxy is about 100,000 light-years. A light-year is the distance of time it takes light to travel. Here is a photo of a spiral galaxy...
The Milky Way...
Some people think the Milky Way is just a band of light. Well, it's not really that. It's actually the plane of the disk of our galaxy.
Spiral Galaxies...
Spiral galaxies are rich in gas and dust. Some are viewed face-on so that the spiral arms are easily seen whereas others are viewed edge-on. These show the presence of dust lanes which obscure the starlight coming from near the midline of the disk. We see this in our galaxy where the Milky Way is divided into two portions for much of its length. The centre of the Milky Way galaxy is invisible in ordinary light because the interstellar dust in that direction is so thick.
