WASHINGTON, November 16, 2013 — Comet ISON, also known as the “Comet of the Century”, unexpectedly brightened Wednesday on its approach to the sun. According to researchers at NASA’s Comet ISON Observation Campaign (CIOC), the comet is now visible to the naked eye. How long it will be visible, however, is unknown.
Charging through our inner solar system, ISON will reach its perihelion, the point at which it comes closest to the sun, on Thanksgiving Day, November 28. At perihelion, ISON will come within 730,000 miles of the sun’s surface.
Forecasters have had a difficult time predicting just how bright ISON will be in the past few months. However, the comet has recently become many times brighter, increasing 16 times in brightness in just 72 hours, according to Space.com.
“ISON has dramatically brightened over the past few days. My own observations from this morning in 10x50 and 30x125 binoculars show a nice ‘lollipop’ comet with a very condensed blue-green head and a long narrow tail,” Carl Hergenrother, acting co-coordinator of the comet section of the Association of Lunar and Planetary Observers, told Space.com on Thursday. “The comet may continue to brighten as the outburst is still in its early stages. Whether this outburst will be a short-lived event or the beginning of a more active phase is still to be seen.”
ISON’s speed at the beginning of the month was about 95,000 mph, and will subsequently reach 845,000 mph by November 28. Cometison2013 is tracking ISON’s distance and speed in real time.
ISON’s recent outburst follows a trend, observed in the past weeks, of short bursts quickly followed by a prompt reduction in brightness.
Will it make history, or be a historic flop?
Discovered in late 2012 and formally known as C/2012 S1, ISON could be spectacular — or a spectacular letdown. For months experts have been warning that ISON will not live up to initial media reports and forecasts of being as bright as the full moon.
“More likely, ISON will be one of the brightest comets in the past several years and, thanks to the global astronomy community, we hope one of the most broadly observed comets in history,” stated a recent status update by researchers at CIOC.
Comet ISON’s core is estimated by CIOC to be between 0.12 and 1.2 miles across. While much smaller than other comets like Hale-Bopp (19 miles) and Halley’s Comet (9 miles), if ISON survives its journey, many are expecting quite a show.
“Another interesting facet of Comet ISON is that it appears to be a dynamically new comet, fresh from the Oort Cloud,” write CIOC scientists on the website. “This means it has probably never been through our solar system, and has never been subjected to the melting effects of solar radiation. It’s a truly pristine example of early solar system material, and thus we are particularly eager to see the combined result of a ‘raw’ piece of solar system material being subjected to the sun’s outer atmosphere.”
However, it may be just because ISON has not been through our solar system before that it may fizzle out unceremoniously.
“Like a light bulb that shines a little too brightly, it may be releasing its ice, dust and gases at a rate that it can not sustain and could lead to it becoming structurally unstable, or simply vaporizing away,” says the CIOC webpage.
Another possibility set forth by the CIOC is that ISON will remain bright through early November, but will get lost in the sun’s glare before reaching perihelion, where it may “outburst,” losing its central nucleus and creating a cloud of dust.
A third and final possibility is that ISON may indeed live up to its “Comet of the Century” hype. While CIOC warns that this possibility is extremely slight, ISON may brighten to become visible to the naked eye in November, before becoming gradually lost in the sun’s glare. It will then brighten significantly during perihelion, where the sun will illuminate its long tail and peak near -8 or -10 magnitude. At this point it may be visible in daylight if the observer covers the sun with one hand.
While ISON is expected to be bright, it will not be brighter than the full moon. After perihelion, ISON could emerge from the sun’s glare as a bright comet with a very long dusty tail visible into 2014.
How to view ISON
ISON will be visible this week in the hour before dawn. While ISON is visible to the naked eye, you may want to use a pair of binoculars or telescope.
Timing: The best time to view ISON is the hour before the sun rises. You can calculate sunrise time for your area here.
Location: It is important to get away from city lights and find clear skies. Dark Sky Finder is a website that shows light pollution in and around North American cities. Clear Sky Chart is a 48-hour astronomer’s forecast that can predict whether the sky will be clear and dark at a certain place.
Where to look: Look east toward where the sun will rise. Comet Watch is a free app that points users in the direction of ISON, updated by the minute.
“The easiest way to find it is to look for Mars, and then draw a line down to the east — right where you think the sun is going to rise,” said CIOC coordinator Carey Lisse to the LA Times.
“If you want to see ISON with your own eyes, do it now,” says CIOC’s website. “We can not and do not guarantee that it will survive the next few weeks and become naked-eye visible in our night skies.”
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