Q: What is latest version of OS X for iMac PowerPC G5?

I have an iMac that I bought just weeks before Apple went to the Intel platform.  It is currently running OS X 10.5.8. 

Here is the info on Hardware:

Model Name: iMac G5

  Model Identifier: PowerMac8,2

  Processor Name: PowerPC G5  (3.1)

  Processor Speed: 2 GHz

  Number Of CPUs: 1

  L2 Cache (per CPU): 512 KB

  Memory: 1.5 GB

  Bus Speed: 667 MHz

  Boot ROM Version: 5.2.5f1

Can someone tell me what is the latest version of OS X that will run on it?