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.
by Fraser Cain on March 13, 2012. Mercury is one of the 5 planets visible with the unaided eye. Even thousands of years ago, ancient astronomers knew that the 5 wanderers were different from the other stars in the sky. The 5 planets visible with the unaided eye are Mercury, Venus, Mars, Jupiter and Saturn. They gave them distinct names, and charted their positions with incredible accuracy.