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.
Orion dominates the winter sky, with blue white Rigel and reddish Betelgeuse at opposite corners and the three stars of his Belt. Hanging from the belt is his Sword, containing the Great Orion Nebula. Some of the stars in Orion are among the most distant stars easily visible to the eye, over 2000 light years away.his scale was originally devised by the Greek astronomer Hipparchus over 2,000 years ago, and the modern version is largely an extended and more accurate version of the ancient scale. Hipparchus called the 20 or so brightest stars in the sky magnitude 1, and stars just visible to the unaided eye are magnitude 6.