Comet ISON: we hardly knew ye
Late last year, hopes began to rise that a Great Comet might be drawing near. Comet ISON (formally addressed as Comet C/2012 S1) looked large, and it was headed for a very close encounter with the sun, which could trigger a fantastic outburst of gas and dust, creating a potentially huge tail for a few weeks after that, perhaps even bright enough to be seen in daylight.
While astronomers were quick to stress the uncertainties inherent in any comet’s outbursts, especially one that had never entered the inner solar system before, and was going to skim so close to the gravitational dynamo at the heart of our solar system, it was easy to also feel their excitement. Guy Ottewell added a “stop the presses” section to his annual Astronomical Calendar to fully illustrate ISON’s potential, and as its sun-grazing moment grew closer, multiple solar observatory satellites were sending near real-time images down to the eager eyes of pros and amateurs alike.
Well, as you likely know by now, the traveler did not survive its close encounter with our local star, the immense ball of plasma that fuels all life on this goldilocks planet of ours. That distant speck of light drew ISON ever closer, growing bright as the comet moved into the inner solar system (realm of the solar body’s rocky fragments: Mars, Earth, Venus, Mercury). A few days before its big moment, our hero began to shudder, showing some signs of partial crumbling; then, in the final hours of its approach, ISON’s dusty nucleus—a half mile or so in diameter, careening into the sun’s magnetic streamers and the pressures of a gravitational force beyond imagination—found it all to be too much, and simply puffed apart.
The last images before it moved too close to the sun to be seen showed it fading fast, and when it didn’t come out the other side as expected, astronomers and skywatchers the world over sighed in collective disappointment. Yet once more, the intrepid dustball surprised, faintly glowing again a few hours later. Yet this was the ghost of ISON, a diffuse patch of dust, continuing along the orbital destiny of its former self, far too faint to be seen by the eyes of earthlings.
These three links honor the memory of ISON in various ways that may be worth your time:
- AstroBob summarizes what we now know of the physical stages of its destruction and shares a time-lapse movie of its approach and retreat from the sun
- A post-mortum Reddit Ask Me Anything session with comet scientists
- Karl Battams of the ISON Observing Campaign offers a short and stirring In Memoriam
And, a few weeks later, this column looks at 10 Lessons from ISON.
Karl’s final words are a fitting conclusion here, as well. This is how Comet C/2012 S1 (ISON) wishes to be remembered:
Images: Damien Peach