Argo

Argo was a sister planet of Krypton, orbiting Rao.

History
When Krypton exploded, its smaller neighbor planet, Argo, was torn from its orbit, and its landscape was devastated by shock waves. After the initial devastation, the world slowly froze for lack of sunlight, causing the deaths of the remaining inhabitants. The Argoans sent distress calls into space, but they were never answered.

Kala In-Ze, Argo's chief physician, placed herself and her family in cryonic stasis, in the hopes that they would survive until help came. Over time, ice gradually encroached on the cryonic cells, destroying all except the one holding Kala's teenaged daughter, Kara In-Ze.

Background information
In the comics Argo City was a city on Krypton and home of Jor-El's brother Zor-El, his wife Allura and daughter Kara. Argo City is also the capital of Argo—not to be confused with Argo City on Krypton, which was introduced in "For the Man Who Has Everything".