August 28 – Enceladus and Alcock

Enceladus was discovered on this day in 1789 by William Herschel. This 500km diameter moon of Saturn has been proven recently to have the most impresive volcanoes in the Solar System. They are cryovolcanoes, so what comes out is cold (in this case water), and study of them has shown that they have been able to project water as far as Saturn itself, as well as providing enough ice to make up the parent planet’s “E ring”.

Enceladus (image credit: NASA)

Enceladus (image credit: NASA)

Enceladus venting, probably as a result of hydrothermal activity.  (Image: NASA/JPL/SSI)

Enceladus venting, probably as a result of hydrothermal activity. (Image: NASA/JPL/SSI)

Enkelados was one of the Gigantes, children of Uranus and Gaia. This particular one, for his sins, was wounded in battle by Athene and buried under Mount Etna.

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George Eric Deacon Alcock MBE was born in Peterborough on August 28th 1912, and became a committed observational astronomer from a young age. He was elected a full member of the BAA in 1936, but had become a member of the meteor section at 18 (shortly after Patrick Moore had joined at age 11).

Alcock spent 20 years watching for meteors before deciding to go after a comet. He also found time to get married, fight a war, and discover, independently of Will Hay (yes, the comic actor) the White Spot on Saturn. His method of discovering at first comets, later novae, was really obvious but almost impossible. Simply memorize the positions of a few thousand stars, then see if anything turns up next time you look at them that wasn’t there last time. This system eventually worked extremely well, with Alcock notching up five comets and five novae. And while this might not sound very impressive compared to some of the asteroid hunters we have met in this blog, to put it in context the last British-discovered comet prior to the announcement ofC/1959/Q1(Alcock) had been 60 years before.

Alcck’s search for a comet began as a New Year resolution. He gave himself five years to accomplish the feat (followed by a further five years and a new pair of binoculars when his time ran out). But comets turned out to be like buses, and no sooner had Comet Alcock 1959e, as it would have been known at the time (there’s been a change to the naming system since then), been discovered, three days before his 47th birthday, than along came 1959f, less than a week later. I can’t imagine how the British astronomical community must have felt to be told about two comets in a week after half a century of drought, but I imagine they were pretty chuffed.

After finding another comet Alcock turned his attention to hunting for novae, again prefering visual observation over the photographic method preferred by his rivals. In one way this actually gave him an advantage over them, as anyone who remembers waiting two weeks to get their holiday pictures back from the chemist will understand. Alcock’s first nova was Delphini 1967 (or HRDel) on July 8th 1967. This was closely followed by another, in Vulpecula, in 1968.

As the years went by, the gaps between discoveries widened, but Alcock never gave up. His last comet and nova were on May 3rd 1983 (comet C/1983 H1 IRAS-Araki-Alcock) and March 25th 1991, aged 78 (nova V838 Her).

George Alcock died on December 15th 2000.

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ALSO TODAY . . . .

Asteroid 167 Urda discovered in 1876 by Christian H F Peters.

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