Unleashing the inner geek put me into a comet coma, I think

I tried photographing Comet C/2011 L4 (PANSTARRS) last week. No joy. It was so close to the Sun there was only a short window to see it in New Zealand, right on sunset, and – it turns out – masked by hills.

Oh well, it’ll be back in another 110,000 years. It was kind of amusing, I suppose – standing on the beach with tripod and camera at dusk. Every so often I’d glance up at Orion to check that Betelgeuse hadn’t exploded yet (one day it will).

Wellington harbour – Port Nicholson/Te Whanganui-A-Orotu, at sunset from Petone beach. The odd colour of the beach shingle is caused by the sodium-vapour street lights behind me, coupled with a 2-second exposure. I was meant to be taking a picture of a comet…

A woman on her evening walk turned up and said to my wife, ‘You a photographer widow? My husband does that too.’

After a while I packed up the inner geek and we went home.

I’ll have another chance with C/2012 S1 (ISON), this November. And in mid-October 2014, ‘Siding Spring’ C/2013 A1 will skim past Mars. Or hit, creating a fireworks show the like of which we haven’t seen for a while – the last was in 1994, when Hale-Bopp ploughed into Jupiter.

We’ve come a long way since comets were seen as harbingers of doom. Or maybe luck. Back in 1861, Gabriel Read, the man who found gold in Otago, thought it a good omen when he looked up with the nuggets in his hand and saw the ‘Great Comet’ of 1861, Not so in America, where the comet appeared just as the Civil War brewed up.

Astronomers took a while to figure out what they were. The key figure was Edmund Halley, a prodigy who became a Fellow of the Royal Society as a nipper, age 22 (the youthful rotten swine!). He paid to have Isaac Newton’s work published, and in the 1690s proved that some comets have closed elliptical orbits. The comet he used to prove the point now bears his name.

Back them, nobody knew what comets were. Now we know they are chunks of ice and rock that usually originate in the Kuiper Belt or Oort cloud, on the edges of our solar system. Every so often, gravitational interferences tip one into an orbit that skims towards the inner solar system, sometimes coming close to the Sun.

Cometary orbits displayed via my trusty Celestia installation. Clockwise from left: Hale-Bopp, Ikeya Zhang, and Halley. The two planets are Neptune and Uranus.

Along the way, an encounter with one of the planets – typically Jupiter – can bend the comet into a shorter period orbit. After a while, the ice and volatiles are burned off by close passes to the Sun, and the comet breaks into trails of gravel. Or it can be broken by tidal forces. There are a lot of variables.

Earth often ploughs through these trails. It’s where regular meteor showers come from, such as the Leonids. These are associated with debris spewing off Comet Tempel-Tuttle, and which we mow through every November.  Usually the chunks are so small they burn up in the atmosphere. But every so often a larger chunk comes through, like the one that burst over Tunguska in 1908. Or over Russia just a few weeks ago.

Have you seen a comet lately? And do you see them as 0mens – or cool science?

Copyright © Matthew Wright 2013

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