Early versions, based on BSD UNIX, were called SunOS. The shift to a System V code base in SunOS 5 was marked by changing the name to Solaris 2 (and earlier versions were retroactively named Solaris 1.x). After version 2.7, Sun began to drop the "2." from the name; the most recent versions (as of late 2001) are Solaris 7 and Solaris 8.
There is also an album called Solaris by Photek.