Wegthor was one of Krypton's moons, which was destroyed prior to the planet's destruction.

Pre-Crisis Continuity

Wegthor was destroyed when Jax-Ur launched a missile into space. The missile deflected off a Krull starship which was piloted by Jor-El, and then crashed into Wegthor, completely shattering the moon. ("World of Krypton")

The Last Days of Krypton

Wegthor was destroyed by a device known as Jax-Ur's hammer in an ancient act of terrorism, centuries before Jor-El's birth. This left visible shattered rubble in the sky. ("The Last Days of Krypton")