Comet ISON Options

[Gladstoner]

Well, here are the orbital elements:

C/2012 S1 (ISON)
T = 2013 Nov. 28.8704 TT
q = 0.012453
Peri.= 345.5614
Node = 295.6595
e = 1.000000
Incl. 62.3643

Current distance from sun = 6.25 au
Current magnitude m1 = 18.0

When I first saw these numbers at http://scully.cfa.harvard.edu/cgi-bin/retu...&o=CK12S010 , I almost thought they were a cruel joke, because they indicate a potentially spectacular comet.

Already, chatter is going on in my favorite comet forum:

http://tech.groups.yahoo.com/group/comets-ml/

[Gladstoner]

Someone asked in PM for some details regarding how and where the comet will appear. But since the PM thing doesn't seem to be working on my end (and keeps eating my sent messages), here goes....

(I'm still at work, so I've had to use duct tape and baling wire to piece together the details of the apparition.)

The comet will move into the morning night sky from twilight as a relatively faint object in early September. It will steadily brighten as it approaches the sun (and the earth). As it accelerates toward perihelion, it will dip back toward twilight from the northwest. It may already be a fine object at this point.

When deep in morning twilight, it may become a brilliant object. At perihelion on November 28, the comet will pass 1/2 degree from the sun. At that time, the standard ephemeris indicates a brightness of -13, which is as bright as the full moon. At these levels, though, the brightness curve breaks down, and all bets are off. If these brightness levels are achieved, the comet will be intense and visible in broad daylight. For those who remember Comet McNaught a few years ago, its appearance in the days after perihelion should be similar, if not better.

After perihelion, the comet will move almost due north from the sun. As it passes through twilight and into the night sky, it should be visible in both the morning and evening sky. If the nucleus survives, the tail will have the appearance of a brilliant searchlight that should extend for tens of degrees at least. Closest approach to Earth will be 0.43 a.u. on December 27 or so, so the month of Demember will be a tradeoff between distance from the sun and distance from the earth.

For the comet fans out there, this one reminds me of the Great Comet of 1680.

Take note: The brightness estimates are uncertain at this point. It is possible that the comet could be a new object from the Oort Cloud, and what is being observed now could be highly-volatile ices subliming from a tiny nucleus that hasn't been close to the sun in the past. In other words, it could be another Kohoutek. If it turns out this comet has had a prior return, then hold onto your hats....

[djellison]

What latitude would suit observers? McNaught was very much for our Southern Hemisphere friends.

[Gladstoner]

What latitude would suit observers? McNaught was very much for our Southern Hemisphere friends.

Pre-perihelion: Northern hemisphere morning, favoring mid latitudes (I think).

Perihelion: Current timing of perihelion indicates daylight visibility for North America (at least) when the comet rapidly rounds the sun.

Post-perihelion: The further north the better, as the comet will be close to due north of the sun before the sun 'leaves it behind' in the morning sky. Mid-northern latitudes should still be more than adequate. It's path in the sky will be more or less similar to that of Comet McNaught for southerners in 2007.

I'm chomping at the bit to get home and enter the elements in a planetarium program. Right now, I'm having to estimate its path across the sky relative to that of the sun.

[dvandorn]

I took a quick look at the open front page of your favorite comet forum, Gladstoner, and seemed to see several people congratulating an Anatoli Nevski for the discovery. Will this be Comet Nevski, then?

Got to be a good connection to be made to Alexander Nevski, somehow, if so. "Oh, noble yeoman, thy tail shineth so bright..."

-the other Doug

[Gladstoner]

I took a quick look at the open front page of your favorite comet forum, Gladstoner, and seemed to see several people congratulating an Anatoli Nevski for the discovery. Will this be Comet Nevski, then?

Got to be a good connection to be made to Alexander Nevski, somehow, if so. "Oh, noble yeoman, thy tail shineth so bright..."

Alexander Nevski.... "Battle on the Ice" would be appropriate music for perihelion passage....

I'm not sure why the International Scientific Optical Network (ISON) got the name rather than Mr. Nevski. Maybe it is a collaborative endeavor, or Mr. Nevski found the comet in the data.

[Gladstoner]

The comet's path across the sky when near perihelion:



The comet will be 'chasing' the sun as both move east. After perihelion, the comet will swing hard to the north.

The tail lengths shown are hopefully approximate.

[Stu]

Ok... STARRY NIGHT is now updating with the orbital elements for the comet, so here are some screengrabs. Use these as a guide to WHERE it will be, and what will be around it. Do NOT take these tail lengths as accurate. Sky rendered for my viewing location in Kendal, Cumbria, UK. Your local viewing circumstances will differ, but if you live in the north this will give you a rough guide...

Basically, pray for a clear sky where you live on Nov 29th...!!!

November 16th before dawn...



November 22nd before dawn...



November 28th before dawn... (McNaught-like tail fan visible before dawn?)



Nov 29th before sunset...



Nov 29th after sunset...




December 2nd after sunset...



Christmas Eve after sunset...



Discuss ;-)

[stevesliva]

Definitely a time of year where Seattle has tons of clear weather.

[Stu]

Definitely a time of year where Seattle has tons of clear weather.

So far...

[Fred B]

This comet makes a very close approach to Mars around October 2nd, 2013, about 0.07 AU. It has the potential for some great photos from MSL or Opportunity! JPL's HORIZONS is predicting a visual magnitude of 2 as seen from Mars at closest approach.

[Explorer1]

That would be an amazing first! Let's hope for clear skies on two planets!

[Gladstoner]

During a close approach to Mars, a 2nd-mag comet would appear as a big, fuzzy ball a degree or so across. It won't have much of a tail at that point.

I'm hoping the real show for the rovers will be a long, skinny tail extending above the Martian mountains some time after perihelion. After all, Mars isn't that much further from the sun than Earth. I'm sure there are some here who could work out the geometry.

[Pertinax]

I would guess that Oppy would have little chance for observing ISON as we would be well on our way toward winter solstice. Curiosity would have a better chance I'd expect? (Assuming reality roughly follows hopes and expectations of course.)

Would a pair of observations of ISON (any comet really) from a known location on mars be notably more enlightening regarding the comet (orbit or visual attributes) than 'ordinary' observations from earth?

-- Pertinax

[ngunn]

Would a pair of observations of ISON (any comet really) from a known location on mars be notably more enlightening regarding the comet (orbit or visual attributes) than 'ordinary' observations from earth?

I think observing from two planets would add information, especially on 3D tail structure. Maybe someone will make an interplanetary anaglyph.