According to the ancient Greek mythology, Callisto, a river goddess, was the daughter of Lycaon, the king of Arcadia. The story says that, she was one of the favourite companions of the moon goddess Diana (Artemis) and used to accompany her on her hunting spree. Like all the other nymphs of Diana, she also took a firm vow to remain a virgin forever. One day Jupiter, alias Zeus, saw the beautiful Callisto and was immediately attracted by her magnetic beauty. He fell head over heels in love with the nymph and became desperate to have sex with her. He was aware that, Diana had warned Callisto about men and gods.
Therefore, to get intimate with Callisto in an easier way, he cunningly disguised himself as Diana and lured her into his embrace. After satisfying his sexual urge, Jupiter flies back up to heaven, leaving a bewildered and shocked Callisto to return to Diana and the other nymphs.
Callisto's consequent pregnancy was discovered several months later, while she was taking a bath with Diana and her fellow nymphs. Diana became very much agitated, upset and enraged, as her obvious pregnancy clearly proved that, despite her oath Callisto had not been chaste. She, therefore, immediately expelled Callisto from her intimate group.
Meanwhile, Juno had already sensed the situation and figured out her husband’s role in impregnating Callisto. However, instead of charging her husband, she aimed her wrath at the poor girl. She waited until the birth of Arcas, the son of Callisto and then vented her wrath not on the rapist, but his victim. To avenge her wounded pride, Juno transformed Callisto into a huge bear. This sudden transformation naturally unnerved Callisto and she ran away in shame from the locality to hide in the seclusion of a forest.
With the passing of time, Arcas grew up to be a handsome young man. When he was about 16, he once decided to go out for hunting, and without knowing anything, went into the same woods where his mother Callisto was hiding. Suddenly, as Callisto unexpectedly saw the young man from a distance, she recognized him as her own child. Overwhelmed with emotion, Callisto forgot about her physical transformation and rushed towards Arcas with open arms to embrace him. However, the unexpected sight of a huge rushing bear in the heart of the desolate forest scared Arcas and for instinctive self protection, he lifted his bow to shoot an arrow at the charging bear, without knowing that, it was none but his poor unfortunate mother.
However, just before it was too late, Jupiter saved them from the inevitable and in the form of a mighty wind tossed them to the dome of the starry heaven and fixed them as the constellations, ‘Ursa Major’ and ‘Ursa Minor’, the big and little bears.