December 15 – Janus

J R Hind discovered today’s main belt asteroid, 23 Thalia, from Hyde Park, London, on December 15th, 1852 (I’d like to see him try that nowadays). Thalia is an S-type asteroid of about 107 km diameter, located between the 3:1 and 5:2 Kirkwood gaps.

In Greek mythology, Thalia, daughter of Zeus and Mnemosyne, with a name derived from the verb “to flourish”, was the muse of comedy and pastoral poetry. She may or may not (depending on which source you believe) have been the mother of the Corybantes, attendants to the Great Mother of the Gods, and associated with particularly orgiastic rites.


We also have a moon today.  The discovery of Janus, one of the inner Saturnian satellites, is attributed to Audouin Dollfus, who first observed it on December 15th 1966. Three days later, Richard Walker also observed an object in the right place but at the wrong time, which caused confusion for a while, but was eventually found to be another moon, Epimetheus, which shares an orbit with Janus.

Janus, photographed by the Cassini probe (image credit: NASA / JPL / SSI)

Janus, photographed by the Cassini probe (image credit: NASA / JPL / SSI)

Janus is the two-faced Roman god of beginnings, entrances, gates, doors, etc. You should thank him the next time an automatic door opens for you. Janus is also one of the select group of deities after whom a month (January) is named, and strangely he has no Greek counterpart.


1965  –  launch of San Marco 1 by Italy. Being their first satellite, the Italians wisely did not fill it with lots of expensive equipment. It did, though, contain a couple of experiments to study the ionosphere, the layer of the atmosphere stretching from about 60 km to 1,000 km, a region you need to know about if you’re planning to become a space-faring nation, needing to send radio messages over great distances.


2000  –  Death of George Alcock, aged 88, hunter of novae and comets. I believe he found five of each (remarkable for south-eastern England), some of them from indoors using binoculars, and even occasionally through double glazing1!  His eyesight must have been unbelievable.


2014  –  Voyager 1 crossed the termination shock.


 

2015  –  Launch of Expedition 46 to the International Space Station.  This caused considerable press interest in my homeland (in fact I’m going to call it a frenzy) because in addition to Russian cosmonaut Yuri Malenchenko and American astronaut Tim Kopra, the three-man crew contained Tim Peake, the first Briton to float into the ISS (I was going to say “set foot aboard” the ISS, but I’ve seen the footage, and feet don’t feature much).  Because of the  numbering system they use at the ISS when crews overlap, these three also formed part of Expedition 47.

ISS Expedition 46 Patch

ISS Expedition 46 Patch

As a supporter of Port Vale FC, I was distraught to discover that one of Tim Peake’s tasks whilst on this mission was to unveil a flag featuring the name of our local rivals, Stoke City.  I’ve gone off him a little.


 

1   Journal of the British Astronomical Association, vol.111, no.2, p.64-66
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