Talthus was a planet in Milky Way galaxy. Talthus was the homeworld of the Talthun. Talthus fell victim to a solar flare of the planet's Star after a dark star passed nearby and engulfed the planet, destroying the planet. The entire population is believed to have been destroyed.
The only survivors were those who fled flare radiation in three sleeping ships on a course for the world Ardena. One of the three, the Stromos, crashed at P2A-347 on the way in 1991, and was discovered by SG-1 in 2003. (SG1: "Lifeboat")