Monday 2 December 2013

Alas Comet ISON, I never knew you

You may well have read my blogs talking about my observations of Comet Lovejoy, but there was always an underlying hint in my writing, I think,  that I was hoping for something bigger and better elsewhere...

My attempts to view ISON were always thwarted. Clear skies at the wrong time, clear skies when I was asleep, a bad horizon from my urban location. I woke up at 5am one day to try and observe it, then probably fell asleep again. A few more days and ISON was much too close to the sun to observe from any Earth based observatories. It was up to the battery of solar observation satellites out in space to try and keep us in the picture.

And it was looking really good, for a just a painfully short time. After some earlier reports suggesting that ISON was already starting to disintegrate, the comet passed through a rough patch, and then brightened rapidly. By the time of perihelion, the comet had reached an estimated magnitude of about 0, and was showing a beautiful pair of tails - a dust tail, and the straighter, narrower ion tail.

ISON just before perihelion 28.11.13, image from NASA SOHO satellite.
ISON then whipped out of view behind the sun for a short time, and observers held their breath. By the time it reached its closest point to the sun, at less than a million miles, ISON was being heated to 4000K and was travelling at 800,000 mph - 0.11% of the speed of light.

ISON was travelling so fast, it was undergoing relativistic effects. Time was running slower for the comet!

Clearly subject to such temperatures and forces, it was never a given that the comet's one mile or so nucleus would survive. Initially, it seemed that nothing had survived, but then this SOHO picture gave hope.

Had Comet ISON (at 11 o'clock) survived?
Something had clearly made it around perihelion, but what?

Hopes were high that some, or perhaps even all, of ISON's nucleus had survived, but then sadly, it became apparent that the image captured above was just a remnant of gas and dust from the comet's tail, with no solid nucleus present. Over the next two days, it gradually smeared out, and disappeared to nothing.

It may be that the comet springs one last surprise on us; the debris around its orbit may give us a new meteor shower when the earth crosses ISON's orbital path early next year. But this is unknown at present.

Comet ISON may be dead, and I may be sad to never have seen it. But the study of this comet, and the interest it generated, was unprecedented, and that is Comet ISON's legacy.

Now get your binoculars out, and look for Comet Lovejoy!

Copyright Cream Crackered Nature 02.12.2013

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