From Imperial Wiki
Asgard from 2003 to when they comitted mass suicide in 2007. In 2004, the planet was attacked by Replicators, but was saved thanks to O'Neill developing the disruptor cannon which was used by Thor to destroy the replicators on the planet. In 2007, th Asgard comitted mass suicide by blowing up Orilla after giving Earth their most advanced technology as well as their entire database. The planet itself is rich in neutronium which is the basis of Asgard technology.