What is our galaxy? How do we know where we are located within it?
The term galaxy refers to an immense collection of stars and interstellar matter, far larger than a star cluster, with typically 10^11 - 10^12 stars. Our Milky Way Galaxy doesn't just contain stars, but also copious interstellar dust. This dust obscures the Galaxy's true dimensions (called interstellar extinction, makes distant objects appear dim).
Our sun is located in the disk of our Milky Way Galaxy about 8,000 pc from the galactic center. This was found using the globular clusters above our Milky Way Galaxy's disk plane. By finding our distance from them as we move using pulsating variable stars like Cepheids and RR Lyrae, we could find the general location of the galaxtic center. Being ablbe to find the distance between us and RR Lyrae was incredibly important, as they are found abundantly in globular clusters of stars.
Globular Clusters are found spread along the the Milky Way and their distributions were three-dimensionally mapped to show us that they form a huge spherical distribution centered not on the Earth, but rather about a point in the Milky Way several kiloparsecs away in the direction of Sagittarius. This point must coincide with the center of the Galaxy.
The Formula for finding the distances of stars:













