Comet ISON in the most recent good resolution image taken by NASA’s STEREO-A probe late on Dec. 3. I’ve processed the photo to better show the comet, which has now become a faint, expanding cloud of dust and small rocks. Credit: NASA
Yesterday morning I dressed for subzero chill to look at comets Lovejoy and Nevski, Mars and a faint supernova in the constellation Leo. Although my hour under the stars didn’t lack in astronomical pleasures, I couldn’t help thinking about ISON. This week was supposed to be the start of that comet’s grand entry into the dawn sky after getting fired up by the sun. Instead we’re hoping to catch a glimpse of its final gasp. When I packed away the telescope and returned to the welcome warmth of my home, I felt a tinge of comet blues.
While you might share my disappointment, the good news is that ISON seems to have just enough oomph to re-appear in the sky before dawn. To date, there have been two possible and one positive sightings:
* Piotry Guzik of Poland strongly suspected seeing a faint 1/4-degree-wide smudge with 10×50 and 15×70 binoculars Friday morning Dec. 6 at dawn.
* A possible picture of the comet was taken by David Rankin also on Dec. 6. Rankin’s image is particularly interesting because it shows maybe-ISON in the correct orientation “lying on its side”. (I just heard this morning that the comet’s position in the photo is off by one degree from its predicted position, making it doubtful we’re seeing the comet. Perhaps it’s a cloud?).
* This morning Dec. 7, J. J. Gonzalez of Spain made what appears to be a definitive observation of the comet with an 8-inch (20 cm) telescope at magnitude 7.2 from his dark, mountaintop location. He described it as 10 arc minutes across (30 arc minutes = one full moon diameter), elliptical in shape and nearly smooth with very little brightening toward its center. Gonzalez also spied two faint, tail-like structures extending to the south and northwest.
I suspect the digital imagers will be out in force over the weekend. We’ll know very soon what ISON’s ghost looks like from the ground.
Michael Jaeger of Austria photographed this tail disconnection event in Comet Lovejoy on Dec. 5, 2013. Comets can lose their tails when magnetic fields entwined with the solar wind snap it off. Like some lizards, a new one quickly re-grows to replace the old. Credit: Michael Jaeger
Comet Lovejoy compensated for whatever twang of regret I felt at not seeing ISON leap over the trees. How fortunate we are to have this picturesque and interesting stand-in for the much-hyped ISON. In my dark eastern sky, Lovejoy could still be seen with the naked eye as a small, “soft” star of magnitude 5.5 in the constellation Corona Borealis. Fainter than a week ago, it will soon fade below the naked eye limit.
Fountains or jets of material launching from the Lovejoy’s nucleus are visible in moderate-sized telescope (8-inches and up) at powers of 200x and higher. This photo taken Dec. 5, 2013. Credit: Gianluca Masi
In 10×50 binoculars a streak of a tail shot up northwest of the bright head. I could trace it for 2.5 degrees. Fascinating fountain-like structures similar to the what you see in Gianluca Masi’s photo sprung up south-southeast of Lovejoy’s core when viewed at high magnification.
After 20 minutes of study I balled my hands into fists inside my gloves to warm them back up and then moved on to Mars.
Lovejoy slowly drops lower and lower in the morning sky over the next few weeks. You’ve got another 7-9 days of good viewing before the full moon returns to the morning sky. Use this chart to help you find it. That’s also the same amount of time left to attempt to see Comet ISON. Because it’s so amorphous and dim, moonlight will almost certainly kill it visually, though amateurs may still be able to get images.
New map for finding Comet ISON shows the sky facing east an1 1/2 to 1 3/4 hours before sunrise for mid-northern latitude skywatchers. The comet’s position is shown daily but marked every 3 days. Stars plotted to mag. 6. Guide stars are labeled: Oph = Ophiuchus, Her = Hercules, Ser = Serpens and CrB = Corona Borealis. Click for a large version. Created with Chris Marriott’s SkyMap software
My original ISON charts assumed the comet would be relatively bright in a twilight sky. This freshly baked map reflects the new reality and shows a lot more stars to hopefully help guide you to your target.
Keep in mind that the map shows the constellation positions for Dec. 7. Each night the stars rise 4 minutes earlier and push up one degree higher in the east. Add that to the comet’s rapid northward motion, and ISON gains altitude quickly in the next week, making a little easier to see each morning … assuming you can see it! On the 7th, for example, the comet is about 6 degrees high at map time; by the 14th, it climbs to 22 degrees.