November 02 – Asteroid 13 Egeria

Annibale de Gasparis discovered today’s asteroid, 13 Egeria, in 1850, named some time later by Urbain Le Verrier in honour of an Italian nymph.

Egeria is, as usual, in the main belt, but is a G-type, not something we get in these pages every week.  G-types are similar to C-types, but are thought to contain phyllosilicates such as clays or micas.  Phyllosilicates get their name from their tendency to form sheets (phyllon is the Greek for “leaf”).

Following occultations of stars in 1992 and 2008 it was decided that Egeria is fairly circular, measuring approximately 200 km in diameter.  It was also one of the seventeen lucky rocks chosen to take part in a University of Hawaii search for satellites and dust rings around asteroids, but none were found.

Egeria Mourns Numa (Claude Lorrain)

Egeria Mourns Numa (Claude Lorrain)

The eponymous nymph shown above was a minor Roman goddess whose origin is unclear (we don’t even know for certain if she was a water nymph or a mountain nymph).   Her cult is known to have been celebrated at several sacred groves, though not usually on her own.   She provided prophecy in return for gifts of water or milk, and was able to divine the sometimes seemingly impenetrable omens sent by the gods.  Her relationship with Numa Pompilius, the supposed second king of Rome (after Romulus) was as a sort of counselor.  Numa supposedly wrote down her teachings and had them buried with him.  When they were discovered by peasants years later, according to Livy, they were thought to be so inflammatory in nature that the Senate had them burned.

1875   ⇒   Discovery of asteroids 152 Atala by the French optician/astronomer brothers Paul and Prosper Prosper Henry, and 153 Hilda by Johann Palisa.

1885   ⇒   Birth, in Nashville, of Harlow Shapley, the American astronomer who correctly estimated the size of the Milky Way, and where the Sun sits within it.  This was achieved using RR Lyrae variable stars, a class of very handy “standard candles” whose luminosity can be used to estimate distances within our galaxy.


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