Our galaxy, the Milky Way, is a spiral galaxy containing approximately 200 billion stars. It is about 1,000 light-years thick and about 100,000 light-years across. It will collide with the galaxy Andromeda in about 4 billion years. It is thought that there are at least 170 billion galaxies in the universe. There are an estimated 700 sextillion stars in the observable universe (a sextillion is a one followed by 21 zeros). The immense scale of these galaxies is beyond comprehension.
Researchers think that the 170 billion galaxy estimate is a lower bound number and that there might be as many as 2 trillion galaxies because there are many more times “dwarf galaxies” than there are galaxies like the Milky Way.
Dwarf galaxies are the most abundant type of galaxy in the universe but are hard to detect because they are relatively faint given their small size. While galaxies like the Milky Way and Andromeda have hundreds of billions of stars, dwarf galaxies usually contain just hundreds of millions to a few billion stars.
The Milky Way is surrounded by over 50 dwarf galaxies, some of which are orbiting the Milky Way and some are being consumed into our galaxy. Dwarf galaxies are thought to be among the first galaxies to form and their stars are typically old and low mass.
In November, researchers announced discovery of a very large (for a dwarf galaxy) and very dim galaxy a mere 425,000 light years from the Milky Way called Antilla 2. Read more about the discovery here.
The biggest of the dwarf galaxies near the Milky Way is the Large Magellanic Cloud (“LMC”). It is about 163,000 light years away and has around 30 billion stars.
Distant dwarf galaxies are hard or impossible to detect because of their faintness. However, there is no reason that the Milky Way is special and it is thought that large galaxies are surrounded by dwarf galaxies just like the Milky Way.