Phaethon thought he was the son of the Egyptian King, Merops, until he mother told him that his real father was the god Apollo.  When Phaethon meets with his friends and tells them this news, they mock him for lying.  So Phaethon goes to Apollo, and asks him if he could ride Apollo’s sun chariot across the sky one day, to prove to his friends that Apollo was his father.  Apollo reluctantly agrees.  When Phaethon got into the chariot, he found that the magical horses were very difficult to handle, and he found him self crashing the Sun into the earth, scarring up the sky, and generally causing a great deal of destruction.  Zeus decided to put an end to all this, and he fired a thunderbolt at Phaethon, killing him, and knocking his body into the sea. 

Phaethon had a very good friend named Cycnus, who, when hearing of his friends death, started swimming in the sea in search of Phaethon’s body.  Swimming like a swan in search of food, Cycnus kept searching for Phaethon’s body, until he became exhausted and drowned.  In order to commemorate this friendship, Apollo place Cycnus in the heavens.