size of character array and size of character pointer

I have a piece of C code and I don't understand how the sizeof(...) function works:

#include <stdio.h>

int main(){
   const char  firstname[] = "bobby";
   const char* lastname = "eraserhead";
   printf("%lu\n", sizeof(firstname) + sizeof(lastname));
   return 0;
}

In the above code sizeof(firstname) is 6 and sizeof(lastname) is 8.

But bobby is 5 characters wide and eraserhead is 11 wide. I expect 16.

Why is sizeof behaving differently for the character array and pointer to character?

Can any one clarify?