Charon

Mass: 1.29 x 10^22 kg
Diameter: 2300km
Mean density: 2030kg/m^3
Escape velocity: 1100 m/sec
Average distance from Sun: 39.53 AU
Rotation period (length of day in Earth days): 6.39
Revolution period (length of year in Earth years): 247.7
Obliquity (tilt of axis): 122.5º
Orbit inclination: 17.15º
Orbit eccentricity (deviation from circular): 0.248º
Mean temperature: 37º K
Visual geometric albedo (reflectivity): ~.5
Atmospheric components: maybe methane and nitrogen
Surface materials: rock, perhaps methane ice

Charon*, is the only moon of the ninth planet in our solar system, Pluto. The moon was discovered in 1978 quite by accident, when routine photographs taken of Pluto showed that the planet had an elongated shape rather then the spherical planet they were expecting. They then noticed that the elongation appeared to change shape over time, moving its position on Pluto's surface. Having ruled out techniqual errors as a cause for the fault, it was concluded they must have discovered Pluto's only moon.

James W. Christy, the astronomer responsible for spotting the anomaly, chose the name Charon for the lonely moon, as this was the name of the the ferryman who transported souls across the River Styx to Pluto's underworld kingdom. (His wife is also called Charlene, which is pretty close too!) Despite it's discovery in 1978, Charon only became an official moon in 1985 after a series of observances were made of transits by Pluto across the surface of Charon, and Charon across the surface of Pluto. These measurements were important to working out what areas of the moon and planet's surface received light from the sun, and at what times. They also helped in working out the separate densities of the two bodies, and from this data it was concluded that the two have formed independantly as Pluto has a very high density, and Charon rather lower density.

Charon and Pluto share the same length of axis, 6.4 days, and Charon's orbit around Pluto is also 6.4 days. Because of this, the planet and the moon always show the same face to one another. Also because of this strange relationship, Charon would appear stationary in Pluto's sky, but could only be viewed on one hemisphere. Unlike Pluto, Charon is thought to have a surface covered in frozen water, whereas Pluto's surface is thought to be that of frozen methane, another possible clue as to how they formed.

* There are several different ideas about how this is pronounced.

• SHAR-on - The unofficial term used by the founding astronomers, as it sounds the closest to Charlene, the wife of Jim Christy who found it.
• liveforever suggests KAIR-on for the English pronounciation, or KAH-ron for the Greek.

For more information on Charon see:
http://www.jpl.nasa.gov/ice_fire/CharonDiscovery.htm
Pictures of Pluto and Charon can be seen at:
http://www.star.le.ac.uk/edu/solar/pluto.html#charon

The ferryman of the dead, and a minor deity, Charon took properly buried souls¹ - for the small price of an obol - from the shore of Cocytus over the river Styx to the rest of Hades, on which side they would be placed in their relevant areas: Tartarus for the wicked; Elysium for the good; and various other areas depending on whose vision of the Underworld you subscribe to.

Heroic Incursions

Apart from the drudgery of shifting souls around, Charon also had a duty to make sure no mortal ever crossed the Styx. Unfortunately, he was notoriously unreliable in this respect, causing a number of Greco-Roman heroes to take advantage and go on a tourist excursion.

Orpheus charmed the grim boatman with his lyre and managed to enter and resurrect his wife Eurydice. Hercules was charged to enter Hades as his last labour, and intimidated the senile sailor into letting him cross. The brute. Aeneas visited Hades for similar reasons, and was able to gain passage by the display of divine will which was his ability to obtain the Golden Bough.² For his leniency toward Hercules, Charon was imprisoned by Hades (Pluto in Roman mythology) for an entire year by being chained to his oar. Which makes one wonder what the souls did while they waited.

The spectre himself

Charon's name almost certainly draws from Acheron, one of Hades' five rivers. He was the son of Erebus and Styx.³ He is universally described as wearing grimy clothes, having fiery eyes and being generally typical of the Underworld.

Probably the finest description, however, is in the Aeneid, in which he is given very human characteristics, perhaps constituting an excuse for eventual leniency toward Aeneas. He is said to be old, but strong, with a grey beard on his chin. His speech is nostalgic, as befits an old man. He is easily swayed by the stronger character of the Sibyl when he puts up an initial resistence to the thought of carrying Aeneas.

Charon's influence

The notion of a grim ferryman, named or not, is very widespread, with the most enduring image in the modern psyche being the skeletal figure in the film Clash of the Titans, conveying the souls across the Styx mechanically and haunting with his flaming eyes.

In contemporary Greek culture, the spirit of Charon lives on as Charontas, the Angel of Death. He is also to be found in Dante's Inferno, a work inspired by Greco-Roman mythology whose influences in modern literature are myriad.

¹ Those who were improperly buried had to wait over a hundred years, which probably wasn't so bad for those destined to go to Tartarus after this time.

² Odysseus also visited the Underworld, but no mention is made in Homer of Charon. It is in Vergil's inclusion of the ferryman that we see not only his debts to other writers and myths, but also his improvement on Homer's Odyssey. Although much of the Aeneid's sixth book draws from the Odyssey, much is added from other authors to give a much more vivid and moving account of Aeneas' visit as a worthy centrepiece to the whole work.
Theseus also visited the Underworld with Pirithous to save Persephone. No mention is made, however, of Charon in the original story.

³ Don't ask me how a river and the personification of darkness can have a child. They just could, OK?

Sources:
The Aeneid
http://www.dl.ket.org/latin1/mythology/1deities/underworld/charon.htm
Various nodes on E2

Cha"ron (?), n. [L., fr. Gr. .] Cless. Myth.

The son of Erebus and Nox, whose office it was to ferry the souls of the dead over the Styx, a river of the infernal regions.

Shak.

© Webster 1913.