Ison 2013

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PostSat Oct 19, 2013 12:24 pm » by DarkHeart


A Commentary on the State of Comet ISON for the Lay Reader


Comet ISON has had the disadvantage of rotating with one pole facing the sun ever since it entered the solar system last year. This means that only a small portion of the nucleus surface area has been heated by sunlight. This may account for it's slow brightening since the July solar conjunction (when it appeared behind the sun, and was therefore unobservable for a couple months). Last Fall and Winter it brightened at a normal comet rate due to sublimation of CO band CO2 (dry ice). Sublimation is the evaporation from a solid to a vapor (skipping the liquid state). Every time a flake of dry ice near the surface sublimated it kicked some overlying dust out, which became the main contributor to the coma's reflected sunlight. Since there must be water ice throughout the comet body some of the ejected material would be ice crystals (snow flakes).

The depth where this could take place is determined by a "thermal wave." Sunlight that is absorbed at the surface heats material on the surface, which in turn heats material in the next layer down, and so forth. The uppermost layer facing the sun is always the warmest, and temperature just decreases as you go deeper. At the present time the hottest place on the comet should be ~ 155 F (68 C), and this would be at the rotational pole facing the sun. Go down a couple feet and the temperature would be much cooler (sorry, I haven't calculated that), probably too cool for sublimating CO2. So all the dust (and snow flakes) being ejected from the comet nucleus comes from close to the surface.

Why did Comet ISON's rate of brightening slow down sometime in June or July? Maybe because the volume of material that was heated enough to sublimate dry ice had become limited by the fact that only one polar region was being illuminated by sunlight. Imagine the "thermal wave" progressing slowly into just a polar region; at first it would convert large expanses of the surface to being warm enough to sublimate dry ice, but the only way for a comet that rotates with one pole facing the sun to convert more dry ice to vapor is for the thermal wave to penetrate deeper. The sides and backside of the comet nucleus remain un-illuminated and too cold to participate in the dry ice sublimation process.


More here (scroll down a bit ) http://brucegary.net/ISON/
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PostSun Oct 20, 2013 1:00 pm » by Shaggietrip


DarkHeart wrote:A Commentary on the State of Comet ISON for the Lay Reader


Comet ISON has had the disadvantage of rotating with one pole facing the sun ever since it entered the solar system last year. This means that only a small portion of the nucleus surface area has been heated by sunlight. This may account for it's slow brightening since the July solar conjunction (when it appeared behind the sun, and was therefore unobservable for a couple months). Last Fall and Winter it brightened at a normal comet rate due to sublimation of CO band CO2 (dry ice). Sublimation is the evaporation from a solid to a vapor (skipping the liquid state). Every time a flake of dry ice near the surface sublimated it kicked some overlying dust out, which became the main contributor to the coma's reflected sunlight. Since there must be water ice throughout the comet body some of the ejected material would be ice crystals (snow flakes).

The depth where this could take place is determined by a "thermal wave." Sunlight that is absorbed at the surface heats material on the surface, which in turn heats material in the next layer down, and so forth. The uppermost layer facing the sun is always the warmest, and temperature just decreases as you go deeper. At the present time the hottest place on the comet should be ~ 155 F (68 C), and this would be at the rotational pole facing the sun. Go down a couple feet and the temperature would be much cooler (sorry, I haven't calculated that), probably too cool for sublimating CO2. So all the dust (and snow flakes) being ejected from the comet nucleus comes from close to the surface.

Why did Comet ISON's rate of brightening slow down sometime in June or July? Maybe because the volume of material that was heated enough to sublimate dry ice had become limited by the fact that only one polar region was being illuminated by sunlight. Imagine the "thermal wave" progressing slowly into just a polar region; at first it would convert large expanses of the surface to being warm enough to sublimate dry ice, but the only way for a comet that rotates with one pole facing the sun to convert more dry ice to vapor is for the thermal wave to penetrate deeper. The sides and backside of the comet nucleus remain un-illuminated and too cold to participate in the dry ice sublimation process.


More here (scroll down a bit ) http://brucegary.net/ISON/




Thank you for posting that DarkHeart. :flop:



Here is update from BPEarthWatch


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http://www.youtube.com/watch?v=1NjR3ZVKjQc




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PostSun Oct 20, 2013 2:06 pm » by Shaggietrip


Not intending to bump. I am up early and Just posting items of interest as I come by them. :look:


Image

On its travel toward the inner solar system the comet must pass through several RED LINES. These RED LINES are the distances at which the specified comets disintegrated. They are shown as horizontal lines. The location of ISON as a function of time is shown by the black dots.
The location of the comet today is shown by the red dot.

The comet passed the red line due to C/1897 U1 Perrine.

The comet should be watched at all times from now on, because is has entered the DANGER ZONE, defined as the interval from the Sun, to the comet with the largest disintegration distance.


Source and more info: http://astronomia.udea.edu.co/cometspage/REDLINES.html



MAGNITUD PREDICTION

Everybody wants to know the brightness of the comet in the next few weeks/months. This is not easy to figure out. Comet ISON is not following the rules and it is following a brightness law quite different from normal comets. After about 40 hours of work, I have been able to complete and update an analysis of the visual and CCD-R data. The details are complex and are presented in the next section. To keep it simple I am going to give the result next. The brightness law that came out for visual observations is:

m(Delta, R, 0) = 8.12 + 5 Log Delta + 2.40 Log R + 0.01 alpha

where Delta is the distance to the Earth, R the distance to the Sun and alpha is the phase angle . This law may be modified as soon as new data comes in.
The law is very very shallow (n=0.97). If fact it is so shallow that it is almost flat ..... again. The brightness prediction using this law is this

Image



The interrogation signs indicate that the comet is entering into uncharted territory and prediction becomes risky.
One thing is clear: the comet is not increasing in brightness significantly, so do not expect a celestial show. The data up to October 16th indicates that this is not going to happen. The prediction shows that it may not even reach to naked eye magnitude.
Sorry folks.


Now the scientific details of this investigation.

Source and Details: http://astronomia.udea.edu.co/cometspage/MAGPREDICTION.html
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PostMon Oct 21, 2013 9:10 am » by *WillEase*



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Scheduled for Oct 28, 2013

Join Slooh's broadcast tem to watch lvie images of Comet ISON as it continues its long journey to its sungrazing encounter in late November. If the sungrazing comet survives its close encounter with the Sun , it may become one of the "Great Comets" - with tails arching over the skies.
Image

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PostMon Oct 21, 2013 11:52 pm » by Shaggietrip


*WillEase* wrote:


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Scheduled for Oct 28, 2013

Join Slooh's broadcast tem to watch lvie images of Comet ISON as it continues its long journey to its sungrazing encounter in late November. If the sungrazing comet survives its close encounter with the Sun , it may become one of the "Great Comets" - with tails arching over the skies.




Thank you for the heads up Will :flop:
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PostWed Oct 23, 2013 1:34 am » by IamSHE


We are all searching for someone whose demons play well with ours.

We met for a reason either your a blessing or a lesson.

How long has it been since someone touched part of you other than your body?

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PostWed Oct 23, 2013 3:11 am » by Shaggietrip


IamSHE wrote:the latest:


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thanks for posting and showing interest, But this particular Comet is not "Ison"



This 'LINEAR' C/2012 X1 was discovered after C/2012 S1 - i.e., ISON. 'S' vs. 'X'. This 'LINEAR' (and there are a lot of comets discovered by LINEAR) is still in the asteroid belt. It will not make perihelion till February 21, 2014. So it is trailing ISON by 3 months.


Source: http://www.sott.net/article/267861-Comet-C-2012-X1-LINEAR-Trailing-ISON-by-3-months-explodes-100x-increase-in-brightness



__________

Comet C/2012 X1 (LINEAR) is currently almost 450 million km from Earth, located in the constellation Coma Berenices. It rises in the east about an hour before the dawn. It is still below the threshold for naked-eye visibility, but bright enough for backyard telescopes equipped with digital cameras.



Image
Source: http://thewatchers.adorraeli.com/2013/10/22/sudden-outburst-of-comet-c-2012-x1-linear/




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PostWed Oct 23, 2013 5:05 pm » by IamSHE


Thx for calling me on this Shaggie!!!
hahaha wrong link try try again......


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We are all searching for someone whose demons play well with ours.

We met for a reason either your a blessing or a lesson.

How long has it been since someone touched part of you other than your body?

ditox tumblr

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PostWed Oct 23, 2013 5:18 pm » by Shaggietrip


IamSHE wrote:Thx for calling me on this Shaggie!!!
hahaha wrong link try try again......


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Now thats more like it. Very cool :flop:
Thank you for posting that.




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PostWed Oct 23, 2013 9:53 pm » by *WillEase*


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