It is said that Antiochus IV forbade Judaism and he invaded Jerusalem and build an altar to Zeus in the Holy Temple. When the Jews reclaimed the temple they lit the ner tamid (eternal light) but only had a jug of oil that would last a day. Instead a miracle happened and the that jug kept the light lit for eight days until they managed to get the new ones. The eight candles on hanukkiah or menorah represent the eight days the fire was lit and the ninth is the one that helps light all the others.
