Comet ISON –
The Mystery Comet of 2013

by Tom Seymour

Comet Hale Bopp, 1997. Comet Hale–Bopp named for two independent observers Adam Hale and Thomas Bopp, was perhaps the most widely observed comet of the 20th century and one of the brightest seen for many decades. It was visible to the naked eye for a record 18 months, twice as long as the previous record holder, the Great Comet of 1811. Tom Seymour photo

A visitor from the Oort Cloud, having traveled from afar, will grace our skies just before sunrise this December. No, this visitor isn’t an extraterrestrial life form, nor is it a UFO. It is, though, definitely a flying object. But it surely isn’t unidentified. It is Comet ISON, and it was discovered on September 21, 2012, by Russian skywatchers Vitali Nevski and Artyom Novichonok, who named it. The two noticed the comet, or what they thought was a comet, while studying images made by a telescope within the International Scientific Optical Network framework. It was indeed a comet and its discoverers gave it the name, “ISON.” The comet’s full name, by the way, is “Comet ISON (C/2012).”

The Oort Cloud, for which ISON came, was named for Dutch astronomer, Jan Oort. It is a sphere-shaped region that encircles our solar system and extends billions of miles out into space. The Oort Cloud contains countless icy, dust-laden globes, many of which may eventually find their way into the inner solar system as comets. And while one estimate puts the number of comets in the Oort Cloud as something like six trillion, these are perhaps 10, 20, 30 thousand miles or more apart.

But why would a comet, or comets, from the Oort Cloud, leave its comfortable orbit and come near enough to planet Earth to give us a heavenly light show? Well, various influences contribute to this. It doesn’t take much to knock a comet out of kilter and send it on a trip through the solar system. Stars, among other objects, occasionally pass close enough to the Oort cloud to exert gravitational force sufficient to tweak an otherwise stable comet’s orbit.

New comets, as in ones on their first swing through our solar system, sometimes make big news in the astronomy community. No one can accurately predict the magnitude, or brilliance of a “new,” or previously-undiscovered comet while it is yet far from the sun. On the day of Perihelion (the point closest to the sun in the orbit of any heavenly body), particularly for a comet making its first close pass, any number of things may occur.

From December 1 through December 5, Comet ISON will be low in the dawn sky at about 30 minutes before sunrise. In the southeast it will be visible higher above the horizon later in the month. Sky and Telescope Magazine. SkyandTelescope.com. 

Cometary Crapshoot

The close pass by the sun has a tremendous effect upon comets, especially first-timers such as ISON. Such comets frequently have an icy covering of extremely volatile matter. As the comet gets ever-closer to the sun, these deposits get cooked off, vaporized, creating an uptick in the comet’s brightness. This brightness quickly dissipates, but not before greatly exciting the hopes of earth-bound observers.

After this, the comet continues on its way toward its tryst with the sun. At this time, for Comet ISON, its early-morning appearances will become increasingly lower in the sky and, according to astronomer Fred Schaff, most likely brighter. But then ISON heads for perihelion, a time when, for most observers (it will be too close to the sun for safe visual observing) it will go out of sight, at least temporarily. But it certainly won’t go out of mind at this time.
Comet ISON’s nucleus (the solid part of the icy head) measures a bit less than three miles in diameter. Lots of other comets are far larger and thus able to retain more integrity during their close pass by the sun. However, some spectacular comets, notably Comet Lovejoy, which reached perihelion on December 16, 2011, had a nucleus only about half as large as Comet ISON.

According to astronomers, it seems likely that ISON will come apart, disintegrate as it gets ripped by the intense heat and gravitational pull of the sun. As disappointing as that sounds, it isn’t all bad news for comet watchers. In fact it could be very good news. It all depends upon how spread out the comet matter becomes.

Here’s what we must wonder about. If the head of the comet disintegrates and becomes too spread out, we probably won’t be able to see it at all. However, if the comet rubble remains closely associated, even if trailed out over a distance, it could brighten considerably. Also, it may develop a long and impressive tail, or tails. This would put it in a class of memorable comets.

And so we wait for the comet to re-appear in the predawn hours of early December.

Comet McNaughton: Many comets are far larger than Comet ISON and thus are able to retain more integrity during their close pass by the sun. However, some spectacular comets which reached perihelion on December 16, 2011, had a nucleus only about half as large as Comet ISON. NASA photo

Early Hype

Comet ISON made big-time internet news shortly after its discovery. Eager comet-watchers hyped it as a possible “comet of the century,” perhaps as bright as the moon. Some made exaggerated statements about its daytime visibility, something not all that common with comets. It happens, but not too often.

But unfortunately, no one had any way of knowing or accurately predicting exactly what Comet ISON would do. But whether it turns out to be a fizzle or a sizzler, ISON has remained a byword among those who would love to view a spectacularly bright comet with an immensely long tail taking center stage in the predawn sky.

And here’s the kicker. Since no one can accurately predict what ISON will look like when it exits perihelion, neither can we say that at least some of the early hype wasn’t true. We’ll only know when it happens, and that is where high drama and great suspense kicks in.

Ideally Located

Even if ISON comes out as a bright comet, people living in densely populated areas may not see much of a showing. Light pollution, the accumulated glare of thousands of street lights and neon signs, tends to cancel out even relatively bright objects in the sky. But some places in the northeast, places such as Maine, don’t yet have much of a problem with light pollution. In fact, Acadia National Park is listed as one of the country’s best places for stargazing specifically because of a lack of light pollution.

Really, anywhere along Maine’s coast (and inland too), people will have a fine opportunity to observe Comet ISON when the big day arrives. The comet, if enough of it remains together in order to put on a show, will be visible in the east-southeast. And who better than fishermen to get a front-row seat for ISON’s post-perihelion debut?

While the comet will, hopefully, present a naked-eye view in December, binoculars or a wide-field telescope will add much detail. For fishermen, setting up a telescope aboard a boat makes no sense. But it seems likely that almost every fishing boat has at least one set of binoculars aboard.

Any binoculars will do, but those fortunate enough to have purchased image-stabilized binoculars will have an edge on others. These tools have excellent optics, coupled with variable-angle prisms that provide optical compensation for wiggles and shakes. Just press a button and the image becomes rock-solid. The author owns a set of Canon 10 X 30 IS (image-stabilized) binoculars and finds them perfect for astronomical observing. But as said earlier, any binoculars will do.

Where To Look

From December 1 through December 5, Comet ISON will be low in the dawn sky at about 30 minutes before sunrise. Considering that your fist held at arms length represents about 10 degrees of width, look at about 4 degrees above the horizon on December 1, 6 degrees up on December 3 and 10 degrees high on December 5. And in case you’re wondering about the accuracy of using a fist at arm’s length, it truly is an accurate measuring device for old and young alike, because arm length increases with age and relatively speaking, the apparent width of a fist at arm’s length always remains the same.

Then beginning on December 7, the comet climbs ever-higher in the pre-dawn sky. Now, we must begin looking for ISON on hour before sunrise. Its brightness diminishes as the month progresses. And when it becomes visible in a perfectly dark, pre-dawn sky, it will have faded to the point that it is no longer a naked-eye object and must be viewed with optical aid.

For fishermen used to every feature of the early-morning sky, once the comet is sighted, finding it again the next day should come quite easily. Also, calculating the exact time of sunrise is made easier by consulting charts. These are available online and also, in the Maine hunting regulations booklet.

Whatever kind of view Comet ISON presents us with, those who see it should know that this is a historic event. No one else has ever seen this first-time visitor to our part of the universe. And probably no one will ever see it again.

For continuing updates on Comet ISON, go to skypub.com/ison.