Thursday, 22 December 2011

Star Gayzing : Capricorn

The Christmas season is full of parties and drinking. Perhaps it is appropriate that the star sign of Capricorn begins today. Capricorn is most often associated with Pan, the chief satyr who resided over wild parties as mentioned last month.

The traditional image of Capricorn is of a goat-fish. Images of the goat-fish appear in Babylonia 4,000 years ago. The Greeks re-interpreted the creature as a manifestation of Pan. One legend, probably created purely to explain the goat-fish image, tells how Pan was attacked by the monster Typhon. In an effort to escape Pan jumped into the Nile. His body under water turned into a fish whilst hi top half remained a his goat-like form.

Pan was also the god of shepherds, and it is in this role that he appears in another part of the sky – the rings of Saturn.

Gaps in Saturn’s rings have been discussed since they were first seen several centuries ago. Astronomers weren’t sure why they occurred until space probes in the 20th century took close up pictures.

In the two outermost gaps in the rings were discovered two tiny moons – the closest to orbit Saturn. Their gravitational forces create the gaps and help to define the edges of the rings. Astronomers call them “shepherd moons”.

The first of these shepherd moons was discovered in 1990, even though it had been recorded on images taken by the Voyager 2 probe in 1981. Because of its nature as a shepherd moon the new satellite was named Pan. It’s a walnut-shaped moon 35km across and 23km high.

In 2005 another small shepherd moon was discovered in the outermost gap in the rings some 3,000km further out from Pan’s orbit. Because it too was a shepherd moon it was given the name of Pan’s boy-lover Daphnis. I’ve mentioned the Ancient Greeks’ attitude to same-sex relationships before in this blog, so it comes as no surprise that Pan had a boy-lover.

Daphnis was himself semi-divine, the son of Hermes and a nymph. His mother had been tricked by Hermes and didn’t want anything to do with the baby so abandoned Daphnis in a laurel grove. He was found and raised by shepherds. As he grew older he became famous for his beauty and music skills. Because of this Pan taught Daphnis how to play the pan-pipes and their love affair began.

In early manhood Daphnis became more of a cowboy than a shepherd, tending to a herd of supernatural cattle belonging to Helios the sun god. He fell in love with a nymph who became jealous of a rival who made a pass at Daphnis, so she blinded him. From then on all of Daphnis’s music was tinged with melancholy, yet sounding even more beautiful than before.

And so the two shepherd moons of Saturn are named after Pan and Daphnis. Closer images of these moons have been taken by recent space probes and show the beauty of their gravitational power over the rings.

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