In Roman mythology, Jupiter was the king of heaven and Earth and of all the Olympian gods. He was also known as the god of justice. He was named king of the gods in the special meeting that followed his overthrow of the god Saturn and the Titans.
Jupiter granted Neptune dominion over the Sea, and his other brother Pluto dominion over the underworld. Jupiter's wife was Juno, who was very jealous of the attention that he paid to other goddesses and women, which is somewhat ironic, as she herself was the goddess of marital fidelity.
Callisto was a river goddess, descended from the river god Inachus. Callisto was the favorite companion of Diana. She accompanied her on the hunt and attended her at her bathing after the hunt.
Europa was the beautiful daughter of the king of Tyre, Agenor. Zeus (Jupiter), the King of the gods according to Greek mythology, saw Europa as she was gathering flowers by the sea and immediately fell in love with her. Zeus transformed himself into the form of a magnificent white bull and appeared on the sea shore where Europa was playing. The great bull walked gently over to where Europa stood and knelt at her feet. The appearance and movements of the bull were so gentle that Europa spread flowers about his neck and dared to climb upon his back. But suddenly, the bull rushed out over the sea, abducting Europa. Only then did the bull reveal its true identity, and took Europa to the Mediterranean island of Crete.
There, Zeus cast off the shape of the white bull, and turned back into his human form, making Europa his lover beneath a simple cypress tree. Europa became the first queen of Crete and had, by Zeus, three sons. At last, Zeus reproduced the shape of the white bull, used by Zeus to seduce Europa, in the stars. Even today we can recognize its shape in the constellation Taurus.
Ganymede was a son of Tros, first king of the classical land known as Troy. One day Jupiter caught a glimpse of the young boy as he was tending sheep on Mount Ida, and was suddenly overwhelmed with a desire to bring Ganymede to Olympus to serve as the cup bearer of the gods. Jupiter therefore changed his shape into that of an eagle, swooped down onto the craggy slopes of Ida, and carried the boy off to Mt. Olympus, home of the gods, to serve as the cup bearer of the gods. Now it so happened that this position was already filled by Hebe, the daughter of Jupiter and his wife Juno. Once Ganymede arrived at the royal court a competition began between Hebe and Ganymede for the honor of serving the gods. Eventually Ganymede won the post, and stayed on also as the favored companion to Jupiter. To honor the events surrounding the elevation of Ganymede to "cup bearer and servant of the gods," Jupiter placed the eagle, a shape he assumed when abducting Ganymede to Olympus, into the heavens as the constellation Aquila (eagle), and immortalized Ganymede as the constellation Aquarius (water bearer).
For the ancient Greeks, the constellation Cygnus, which means "swan", was related to the myth of Zeus and the goddess Nemesis. In order to escape from Zeus, Nemesis changed herself into many different animals. When she changed into a goose, Zeus immediately transformed himself into a wonderful swan and won the love of Nemesis. The goddess became pregnant, delivered an egg and then abandoned it. Fortunately, a shepherd found the egg and gave it to Leda, the wife of Tyndareus, the king of Sparta. From that egg came Helen of Troy. Helen was so beautiful that Leda claimed her as her own child. The constellation Cygnus was formed to celebrate the lovely swan. According to another version of the myth, Zeus transformed himself into a swan to court Leda, the queen of Sparta, and from that relationship, Leda had two children: Polydeuces and Helen.
Io was a priestess of the Greek goddess Hera. Hera was the jealous wife of Zeus, the king of the gods. Zeus was very unfaithful. When Zeus fell in love with Io, he changed himself into the shape of a dark cloud to hide himself from his jealous wife, Hera. However, Hera looked down on earth and noticed the small cloud. She knew it was her husband. As soon as Hera arrived, Zeus immediately transformed Io into a white cow to protect her from his wife's wrath. But Hera tied the poor cow and sent her faithful servant Argus to watch over Io. Argus had a hundred eyes and only a few were ever closed at any time.
To free Io, Zeus sent his son Mercury to sing and tell boring stories to make Argus sleep fully, closing all his eyes. Mercury told so many stories that finally Argus close all his hundred eyes. Only then did Mercury kill Argus and untie Io who ran home free. Yet when Hera discovered what had occurred, she was so furious that she sent a vicious gadfly to sting the cow forever. She also commemorated her servant by setting his eyes in the peacock's tail, and the bird became her symbol.
Meanwhile, Io who was still prisoner into the shape of a cow could not get rid of the malicious gadfly. Finally, after Zeus vowed to no longer pursue his beloved Io, Hera released Io from her inhuman prison, and Io settled in Egypt, becoming the first queen of Egypt.
The Jovian moon Io was named for the mythological character Io by Johannes Kepler, and Simon Marius. And finally, when Voyager 1 passed Io in March 1979 and imaged the surface, the image clearly showed the hoof print of a heifer!