Alderaan was a terrestrial planet located in the alderaan system, This planet served as the home planet to bail organa and Breha Organa and soon to be where Princess leia organa is relocated at birth
A New Hope[]
During 0 BBY grand moff tarkin sets the death star course to the alderaan system, Tarkin later on desides to destroy the planet to set an example and strike fear into the rebels Killing over 1 Billion people.
After A New hope[]
Shortly after a new hope Lord vader brings whats left of the planet right before the newly crowned queen trios to show her what happens when the emperor's authority is challenged.