May 06 – Daphnis

Today in 2005, Saturn’s moon Daphnis was discovered by the Cassini team.

Daphnis (image credit: NASA)
Daphnis (image credit: NASA)

Don’t be fooled by the large object at the bottom of the photograph: that’s Epimetheus, a moon about twelve times wider than Daphnis.  The birthday boy himself is a tiny, barely discernible dot towards the centre of the frame.  You might be surprised by the use of the word “boy” there, assuming Daphnis might be named after a Daphne.  But it wasn’t.  Daphnis was a shepherd (this is a shepherd moon), a very good friend of Pan, and the inventor of pastoral poetry.

Apollo and Daphnis (Perugino).
Apollo and Daphnis (Perugino).

The moon Daphnis, being ridiculously small, wasn’t an easy target to photograph. Fortunately, though, its position in the Keeler Gap within Saturn’s A ring gave it away by causing ripples within the ring. In order to stay within the Keeler Gap, Daphnis has to follow a near-perfect circular orbit. The difference between Daphnis’ perikrone and apokrone (closest approach to and furthest distance from Saturn) is only about 9 km (under 6 miles).

 1896  –  Asteroid 417 Suevia discovered by Max Wolf. Suevia is a K-type/S-type main belt asteroid of approximately 41 km (25.4 miles) diameter. it sweeps serenely round the Sun in an orbit ranging from 363 to 474 billion miles.

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