Details. as.character and is.character are generic: you can write methods to handle specific classes of objects, see InternalMethods. Further, for as.character the default method calls as.vector, so dispatch is first on methods for as.character and then for methods for as.vector.
But this is the number of stars we can see from the entire Earth and we should remember that one hemisphere of Earth is always in daylight, so really only about 2500 to 5000 stars are visible at night from any given point on Earth.
Yes, all the visible stars are in the Milky Way. It takes a huge telescope and long time exposures to resolve stars in other galaxies. In fact, the farthest star we can see with the naked eye under the best of conditions is probably epsilon Aurigae-A, which is almost 8000 light years away.