The End of Comet ISON? main content.

The End of Comet ISON?

by Steve Beyer on


Comet ISON C/2012 S1
Comet ISON C/2012 S1, Hubble image from October 9, 2013
NASA, ESA, and the Hubble Heritage Team (STScI/AURA)

During these last days of November, much discussed Comet ISON continues to accelerate toward its solar rendezvous Thanksgiving Day. The comet’s closest approach to the Sun will be at 1:14 pm EST, when many of us are thinking about turkey dinners. Although this much ballyhooed comet has just barely become visible even with the help of binoculars, ISON is indeed a remarkable object. This is in large part due to early speculations it might be “The Comet of the Century,” and to resulting wide attention by researchers applying an unprecedented array of observatory hardware.  Multiple efforts are underway to glean information about the nature of ISON, and discover clues its pristine composition may reveal about the early Solar System when it was formed.

Although some have personally seen ISON’s glow in predawn autumn skies, its unremarkable appearance, vagaries of cloud cover, and increasing involvement with predawn twilight have frustrated many others who had hoped ISON would put on a spectacular celestial show. That still might be a possibility if the Sun stirs things up during the perihelion approach on November 28th.  However, the Sun might tear ISON apart as it approaches and totally destroy the object, which is about the size of Manhattan. On the other hand we may get lucky, and early the following morning of November 29th (which happens to be my 70th birthday), we might look toward the eastern horizon and witness several remarkably bright comet tails streaming upward from the horizon, these plumes heralding ISON’s safe escape from its solar adventure.

I recommend starting a few days before the morning of the 29th to scout and locate a suitable vantage site where you might observe ISON, if it survives, on the first pre-dawn morning after perihelion. Try to find a spot as far as possible from buildings and trees as you look east.  Remember the height of your fist held at arm’s length is about equal to 10 angular degrees, and horizon obstructions should be not much higher than that. The eastern direction should also have minimum interference from ground lights. Such vistas are not easily found in urban areas, but views over large bodies of water and parklands often provide the best solutions. If things play out well,  we may still be treated to several weeks of memorable comet watching during December.

Aside from the actual sky, I suggest connecting with NASA's Solar & Heliospheric Observatory and Solar Dynamics Observatory for dramatic comet viewing during ISON’s encounter with the Sun Thanksgiving afternoon. You might like to check these sites beforehand for familiarization, so on Thanksgiving Day you can quickly cut to the chase and witness perihelion events live.