Pi orbital is a period 168 oscillator that was found by Noam Elkies in August 1995. It works by using four crowns and four blocks to turn a pi heptomino ninety degrees every 42 generations. A second pi heptomino can be inserted to reduce the period to 84. On March 26, 2009 Nicolay Beluchenko found a relatively small period 12 sparker that could replace the crowns.
Generation 27 reveals the pi heptomino
An alternate version of pi orbital using Nicolay Beluchenko's period 12 oscillatorRLE: here