September 02 – 147 Phaedra

Discovered on September 2nd 1877 by James Craig Watson, 147 Phaedra is a bog-standard S-type (stony) asteroid, possibly with an elongated shape, in the main belt.  It takes approximately 4.8 years to get around the Sun, rotating every 5 hours as it does so.  Phaedra has a diameter of less than 70km, so determining the rotation rate by direct observation from Earth is, to say the least, difficult.  This is where light curve observations come in.  If you measure the light coming from an asteroid for long enough you end up with a collection of readings that, when plotted on a graph, repeat every so often.  What you need to do is measure the time between similar maxima or minima to give you a pretty good idea of the length of a day on the asteroid.  By the way, a rotation rate of 5 hours gives Phaedra a year of about 1700 days.  You’re going to need a bigger diary if you’re thinking of moving there.

Watson discovered 22 asteroids, but could have gone on to be one of the great rock-spotters had he not died of peritonitis at the age of 42.

Phaedra and Hippolytus (print by A G L Desnoyers of a painting by Pierre Guérin)

Phaedra and Hippolytus (print by A G L Desnoyers of a painting by Pierre Guérin)

Phaedra (from the Greek for “bright”) was married to Theseus, but fell for his illegitimate son Hippolytus (eponymous hero of a play by Euripides that I was forced to spend far too long studying in 1981) under the influence of Aphrodite, goddess of love, who was annoyed by Hippolytus’ chastity.  Basically, Phaedra makes the mistake of telling her nurse that she fancies her stepson.  The nurse tells Hippolytus; he goes ballistic; Phaedra knows things are going to get complicated, hangs herself and leaves a suicide note saying Hippolytus has raped her.  Theseus finds it, exiles his son and curses him.  Now, Theseus’ father is Poseidon, so it’s not quite the same as me or you cursing a neighbour for parking in front of our house.  In this case, as Hippolytus is fleeing into exile in his chariot, a huge bull appears from the sea, frightens his horses, and causes him to crash and be fatally wounded (he survives just long enough to be carried back on stage to make peace with his father, who has learned the truth).

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