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View Full Version : C/2012 S1 (ISON) - the next Great Comet?



Don Alexander
2012-Sep-24, 08:54 PM
In CBET 3238, the IAU reports the discovery of comet C/2012 S1 (ISON).

Now, comet discoveries are run-of-the-mill, but this one is special!!

- The orbit is almost perfectly parabolic, it is e = 0.999999964 - this implies the comet came from very far out and is possibly an Oort cloud comet. Such comets are usually on their first dive into the inner Solar System and are thus still loaded with volatiles (but can fizzle like Kohoutek...).
- The perihelion (in late November 2013, it seems) is at q = 0.012453 AU!! This is just a few solar radii out!! A Sungrazer!
- It will pass 0.4 AU from Earth in January 2014!
- It will never go more southerly than Dec. = -22, so should be well-observable from both hemispheres!!

All in all, this is the recipe for a possible Great Comet!! :D It's reasonably likely to be a naked-eye object at least, and maaayyybe it will be similar to McNaught!

Let's see what the future holds.

Jerry
2012-Sep-24, 09:45 PM
Sweet - How soon will we have a name? The great comet of 2014 - beam me up!

Don Alexander
2012-Sep-24, 10:20 PM
It has a name: ISON.

"Vitali Nevski (Vitebsk, Belarus) and Artyom Novichonok (Kondopoga, Russia) report their discovery of a diffuse comet with an 8" coma on four 100-s CCD exposures obtained on Sept. 21.06 UT with a 0.4-m f/3 Santel reflector of the International Scientific Optical Network (ISON) near Kislovodsk, Russia."

Swift
2012-Sep-25, 01:27 AM
All in all, this is the recipe for a possible Great Comet!! :D It's reasonably likely to be a naked-eye object at least, and maaayyybe it will be similar to McNaught!
:dance:

As my mother-in-law would say, from your lips to god's ear. ;)

I've been wanted a great comet for a long time. Let's hope.

Ara Pacis
2012-Sep-25, 07:41 AM
Should we and can we send a probe to it?

Don Alexander
2012-Sep-25, 08:32 AM
Extremely unlikely. Considering all the recent budget cuts, the typical time it takes to build a spacecraft, the almost inevitable delays...

Superluminal
2012-Sep-26, 12:08 AM
Extremely unlikely. Considering all the recent budget cuts, the typical time it takes to build a spacecraft, the almost inevitable delays...
A mission idea I had, but NASA would never go for: A flyby craft on a rocket placed on alert, similar to the way nuke missiles are on alert. The rocket could be readied and launched in a few days to rendevous with any potential Oort cloud visitor, such as ISON. We've seen plenty of short period comets, we're yet to take a close look at a long period comet. Think what we could've learned from a visit to Hale-Bopp, Hyakutaki or any number of long period comets making their first pass through the inner solar systym? Of course there would be risks. If we launched a probe to a comet such as Comet Elenin. The comet might disentergrate before we get there. And the costs of maintaining a rocket that may just set there for several years waiting on a suitable comet to come by.

Swift
2012-Sep-26, 01:36 AM
Website with some of the first images (http://remanzacco.blogspot.it/2012/09/new-comet-c2012-s1-ison.html)
Got the link from spaceweather.com

Don Alexander
2012-Sep-26, 07:37 AM
Looks like the Internet is all abuzz now about it. (http://www.universetoday.com/97578/guest-post-comet-kerfuffle/)

Remember, you read it here almost first. ;)

So speculations have been shooting up that it could rival Ikeya-Seki or even the Great Comet of 1882... We'll see. Hold your horses.

Alas, it will take at least a few months before any better predictions are available.

In the meantime, let's look forward to Comet PanSTARRS! :)

Perikles
2012-Sep-26, 08:47 AM
OK - I'll ask the dumb question. If its only near approach to Earth happens after its perihelion, after it has grazed the sun, isn't it likely to have completely fizzled to nothing by then?

Don Alexander
2012-Sep-26, 12:01 PM
I'm not sure if this is the rule for all comets, but sungrazing ones usually are a lot brighter going out than going in, see for example Comet Lovejoy:

http://www.aerith.net/comet/catalog/2011W3/2011W3.html

It's likely still well observable when it passes Earth, unless it completely disintegrates.

peteshimmon
2012-Sep-26, 02:26 PM
Dont normally think about comets, parochial
stuff! But I wonder, it is frozen solid until
the Sun grazing, would a non rotating body
give a brighter tail?

Centaur
2012-Sep-26, 07:46 PM
Iíve created seven charts with graphics and data for Comet C/2012 S1 (ISON). Included are seven more charts for bright Comet C/2011 L4 (PANSTARRS) which is due earlier in 2013. They can be seen on my comets webpage at: www.CurtRenz.com/comets

Based on very preliminary JPL parameters, Comet C/2012 S1 (ISON) would peak at magnitude -15.7 when at perihelion on 2013 NOV 28 at 20:51 UT. However, at perihelion the comet will be only 0.0125 AU from the Sun, placing the comet too close to the Sun at that time to be observed by naked eyes or the telescopes of amateurs. The comet's brilliance will be considerably dimmer during the days on either side of perihelion.

Here are my calculated magnitudes based on current JPL parameters at 00:00 UT during late 2013.

NOV 20 +01.2
NOV 21 +00.8
NOV 22 +00.3
NOV 23 -00.2
NOV 24 -00.8
NOV 25 -01.5
NOV 26 -02.5
NOV 27 -03.9
NOV 28 -06.4
NOV 29 -13.1
NOV 30 -05.6
DEC 01 -03.6
DEC 02 -02.4
DEC 03 -01.5
DEC 04 -00.9
DEC 05 -00.4
DEC 06 +00.0
DEC 07 +00.4
DEC 08 +00.7
DEC 09 +01.0
DEC 10 +01.2

During the above dates until about 2013 NOV 25 the comet should be visible by naked eye above the southeastern horizon shortly before sunrise. It's not until about DEC 06 that the comet should be visible by naked eye above the western horizon shortly after sunset and again in the east before sunrise.

publiusr
2012-Oct-06, 06:04 PM
We are lucky to be alive now. Hale Bopp and now this. Great stuff.

Romanus
2012-Oct-08, 08:59 PM
According to JPL's HORIZONS ephemeris, ISON will get as close as 11 million km to Mars on October 2, 2013. If the teams in charge of MRO and Curiosity are so inclined, they may get some spectacular views of a comet in another planet's sky.

Don Alexander
2012-Oct-14, 09:36 AM
I suspect the comet will not yet be very active at this time, and therefore might not be observable.

Kullat Nunu
2012-Oct-21, 03:43 AM
Comets have traditionally been notorious what comes to brightness predictions... but since this one was detected so far away, it is more likely it is genuinely a large one which really can give us a good show.

Centaur
2013-Jan-28, 11:29 PM
JPL has recently changed the magnitude parameters for C/2012 S1 (ISON). Peak brilliance at perihelion has been downgraded from -15.8 to -13.0. As I posted earlier, the comet will only be especially bright when too close to the Sun to be observed by the masses. The media have become hyperbolic, as usual. Space.com is writing articles about how bright two comets will be this year. They do include a few caveats, but as might be expected, many readers only remember the superlatives. On various blogs they are talking about how night will become as bright as day. More conservative reporting would have allowed the public to become pleasantly surprised. Instead, they may become deflated.

Iíve updated my graphics for the comet to reflect the new magnitude estimates. They can be seen at: www.CurtRenz.com/comets

MechaMadness
2013-Feb-06, 05:13 AM
I am ecstatic and cant wait! I wrote on sign on my wall next to my light switch reminding me, even though that comet will be brighter than the moon and OBVIOUSLY visible!

Centaur
2013-Feb-06, 06:23 AM
I am ecstatic and cant wait! I wrote on sign on my wall next to my light switch reminding me, even though that comet will be brighter than the moon and OBVIOUSLY visible!

Calm down. It may not be so obviously visible. It will only be that bright when too near the Sun to be viewed. The media hype may once again lead to disappointment. If they were more conservative in their reporting, the public may be more appreciative of what actually does come our way. www.CurtRenz.com/comets