We are particularly fond of the Milky Way because it is the home of the Sun and the Earth (as well as another 100 billion other stars and still more planets).
The Milky Way forms the cornerstone against which we base our understanding of how other galaxies might work in detail. The question is: can the Milky Way be described as a typical spiral galaxy?
There are a few signs that the Milky Way may be a bit different from its neighbors. One clue comes from looking at the galaxy centers. All massive spiral galaxies like the Milky Way are found to harbor giant black holes, except that for the Milky Way this central supermassive black hole is smaller.
Another clue comes from an investigation of the surroundings of spiral galaxies. The Milky Way has dozens of very small galaxies in its immediate vicinity which we call satellites. Many of these satellites have been discovered only very recently as they are very faint owing to there being very few new stars being formed in them. At the same time, other nearby spiral galaxies have satellites that sustain much higher rates of star formation.
A new investigation is underway to increase our understanding of these differences, called the Satellites Around Galactic Analogs (SAGA) Survey led by a team at Yale University.
Learning about the differences between the Milky Way and other galaxies, if any, may help us to better understand our place in the universe.