Will Comet ISON dazzle or fizzle in the morning sky?

Roy Gephart, StargazingNovember 24, 2013 

Some cherished Thanksgiving recipes for preparing that perfectly baked turkey or those award-winning sweet potatoes are handled like CIA secrets, only passed to family members on a need-to-know basis.

This protects those culinary delights from being published in church cookbooks, tucked inside the family’s bible under Revelations, or disclosed to Uncle Bill’s fourth wife.

As the aroma of baked ham, spiced stuffing, hot rolls and pecan pies draws families together this Thanksgiving Day, something remarkable is also taking place overhead. A 4-mile-wide potato-shaped chunk of ancient rock and ice has begun plunging through the insane, iron-melting heat of the sun’s upper atmosphere.

This object is called Comet ISON, and it is attracting considerable scientific and public attention.

In 2012, two Russian astronomers working for the International Scientific Optical Network (ISON) discovered this comet lurking near the orbit of Jupiter. Plots of the comet’s path revealed it headed for a 2013 rendezvous with the inner solar system and most importantly with the sun.

Soon after discovery, rumors, speculations and a new round of doomsday prophecies mixed with educated estimates about the comet’s possible fate populated the Internet. Suspicions of ISON glowing brighter than the full moon soon fell apart as the comet remained fainter than expected.

Thanksgiving Day marks ISON’s closest encounter with the sun — a perilously close 700,000 miles above the bubbling caldron of the sun’s surface. Here, comets quickly learn whether their fate is to survive or to disintegrate.

Comet ISON spends a few days in this hellish setting before the immense gravitational sling-shot effect gained from sun’s mass flings the comet outward high above the solar system to forever return to the frigid darkness of deep space.

As of this writing, the good news centers on reports rolling in that Comet ISON is brightening and growing more visible to the naked eye. Almost each day gas and dust flare-ups are brightening the comet.

The bad news is that comets are notoriously fickle, especially for a comet like ISON apparently making its first sojourn into the solar system.

Plots of this comet’s hyperbolic (open ended) path suggest ISON originated far away — from inside the spherical shaped reservoir of icy debris astronomers speculate remains from the birth of our solar system.

That region, called the Oort Cloud, is parked about one light year distant from the sun. This is about one-fourth the distance to the nearest star.

The best way to remain informed about Comet ISON and to know where to look in the morning sky is to go online. I suggest searching under “Sky and Telescope + ISON” to read the latest observing blogs.

General star charts, like the one accompanying this article, are perfect for the casual observer to search in the right area of the sky to find Comet ISON.

More detailed maps depicting comet locations against a background of stars are preferred by experienced observers. In either case, binoculars are your friend.

The best time to observe Comet ISON is near the first hint of dawn during the two days of November through early December. Search within a few hand-widths above the southeast horizon.

The sun’s pre-dawn glare will hide ISON starting about Nov. 27. However, the comet will reappear about Dec. 1 just left of where the sun rises.

Comet ISON faces several possible outcomes as it swings around the sun-total destruction, partial destruction, initial survival followed by breakup, or total survival.

Informed wagers suggest survival. Many reliable sources believe ISON will survive its gravitational, oven-fired battle with the sun.

Nonetheless, astronomers remain cautious about predicting too much. They still recall the debacle of 1974, when the comet-of-the-century hype heaped upon Comet Kohoutek fell far short of expectations.

Comet Kohoutek fizzled because it partially disintegrated when whirling around the sun and did not develop a bright dust tail that reflected sunlight.

Comet ISON needs to survive its encounter with the sun and develop a vivid dust tail to grow into an eye-catching object caught within the autumn light of early dawn.

I’m betting on the first week of December to offer the best views of ISON. Let’s keep our fingers crossed for a couple of clear morning skies.

— Roy Gephart is a retired environmental scientist and avid amateur astronomer.

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