This year we have two comets that are predicted to be naked-eye observations. ISON, full name C/2012 S1 ISON is the brightest of the two and possibly visible during the day in November! November is a way off you say but imaging and observing comets for detail requires a learning curve. And you may just have a chance to learn in March with Comet PanSTARRS (C/2011 L4 PanSTARRS) which is predicted to be magnitude 2.0 or brighter according to the latest light curves by comet observer Jakub Cerny. On the left (top) is the sky chart for comet PanSTARRS and will have a chart for ISON in a future issue.
Note: Planetarium software such as Starry Night or Sky Safari is updated with these comet positions so you can track them.
In 1997 sixty nine percent of US population (that’s 194 million of your neighbors) saw comet Hale-Bopp. Together with long-tailed comet Hyakutake, the duo commanded the night sky and spiked an interest in astronomy worldwide that has clearly rippled to the present. For some of our readers, these comets are why they are SJAA members now.
Before you read on let me share the first characteristic you should know about comets: they are notoriously unpredictable. Where comets Hale-Bopp (left, seccond from the top) and Hyakutake (left, third from the top) exceeded predictions more comets fail to dazzle the public. To quote amateur comet hunter David Levy, “Comets are like cats: they have tails, and they do precisely what they want.” Nevertheless amateurs astronomers with telescopes often feel the dazzle precisely because they have a telescope.
For some veterans of our hobby Hale-Bopp and Hyakutake turned them out-side-in. After witnessing these comets naked-eye and then following their departure from the inner solar system, deep-deep sky aficionados, who search for galaxies out beyond our local group some 65 million light years away, started to scan the shallow skies to get their comet fix. Why deal with withdrawal if you don’t have to? It didn’t matter if the comet’s magnitude was 12 or fainter – that’s within the magnitudes they work in anyway. The distance however is another story. The origins of most comets can be traced to icy Oort cloud which extends out to 50,000 AU from the sun. That may be quite a distance for a NASA satellite to cover but to an astronomer with a telescope, it’s just shy of one measly light year.
In 2008 amateur astronomers Xing Gao and Tao Chen (China) discovered a 12th magnitude comet with a digital SLR camera attach to their scope. They found comet, now named C/2008 Chen-Gao (on the left, second from the bottom), in the constellation Cepheus during their novae search. It was missed by the professional community doing asteroid surveys because it was within a star-rich area they tend to avoid. Too much clutter.
Comets are not always that faint of course. Some of you may have had the pleasure to observe comets Machholz or Holmes when they were quite bright. Comet Machholz was discovered by amateur astronomer Don Machholz from Colfax, CA in 2004. It reached naked eye brightness in January 2005. In 2007 Comet Holmes unexpectedly brightened from a magnitude of about 17 to about 2.8 in a period of only 42 hours. For myself and my friend, we heard about comet Holmes but did not bother to read the details of where is was or how bright it got. We were on a lunar photography trip. Our mission was to catch a full-moon set at dawn over a field of a couple thousand of Sandhill Cranes. Our goal was to image a real shot of an ET (Earth Terrestrial) flying in front of a full moon and we logically picked cranes because of their mass break of dawn fly-outs to nearby grazing fields. On our pre-dawn drive to the site, the moon was hidden behind some foothills so we made a quick stop to do some observing. I was scanning the skies around Perseus with my binoculars when I stopped at something very strange. The star arrangement was all wrong. Either a new star had suddenly brightened to rival Algol or we actually have an ET! Naturally my friend and I could not believe either so we put our scope on the object. A fuzzy blue green sphere was in the field of view and within a few long seconds of gear grinding we realized to our delight we discovered Comet Holmes. Well, OK we didn’t actually discover the comet but you know what we mean – we discovered it for ourselves. We upped the eyepiece power to view its structure with the right amount of contrast and magnification and we dispensed with the idea that it was perfectly round as was our first observation. The head of the comet inside its bubble of gas was slightly off center. Moreover we could get the hint of a comet tail, short but just poking out of the gas shell. All-in-all our best description of the comet was that is looked like a glowing blue transparent salmon egg. You cold see the salmon embryo inside and in fact its tail was sticking out. It was about to hatch. To learn more about observing comets visit Martin McKenna’s webpage at http://www.nightskyhunter.com/An Observing Guide To Comets.html. For weekly information on all the bright comets visit Seiichi Yoshida’s webpage at http://www.aerith.net/comet/weekly/20130112n.html.
By the way we did finally get our shot of ET flying in front of the moon. (On the left, bottom) A final note on comet research: A number of recent space missions have ventured to comets. NASA’s Deep Impact collided an impactor into Comet Tempel 1 in 2005 and recorded the dramatic explosion that revealed the interior composition and structure of the nucleus. In 2009, NASA announced samples the Stardust mission returned from Comet Wild 2 revealed a building block of life. The European Space Agency’s Rosetta is scheduled to orbit Comet Churyumov-Gerasimenko in 2014 and deploy a probe to make the first landing on a comet.
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