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Comet C/2012 S1 ISON

Lohan2008

By Lohan2008
in Science & Spaceflight

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lajoswinkler

lajoswinkler

Posted
Posted (edited)
Presumably the oxidation of the dirt in the dirty snowball as it burns up.

(go to 2 hours and 6 mins to 2 hrs 12 mins) to hear the SDO guys talk about oxygen.

There's nothing burning up there. Proper burning in oxygen requires significant pressures, molecular oxygen and condensed fuel. This is the glow of ionized oxygen coming from the comet's water. H2O decomposes photolytically when bombarded with Sun's high energy rays and gives several different ions, all having their emission and absorption spectrum.

It's quite similar to what happens in aurora borealis.

Comets don't even evaporate. They sublime. They're made out of ices (water, CO2, ammonia, ....) and rock (silicates, metals) and they turn directly to gas (if they come too close to the Sun, the rock boils, but for most part, nothing is boiling). In the vacuum of space, having very weak gravity, their atmosphere extends in a coma and is pushed by the Solar wind away.

I sincerely doubt ISON will be very visible in the sky. It's obvious this is a fragment we're seeing in the images.

Edited by lajoswinkler
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Geschosskopf

Geschosskopf

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I sincerely doubt ISON will be very visible in the sky. It's obvious this is a fragment we're seeing in the images.

Yeah, this is pretty much a bummer. After 2 weeks of cloud and rain, we've got a clear stretch for the next couple of days so I was hoping to see a nice show. I'll give it a try but I'm not hopeful.

I'm just glad I saw it when I had the chance back on 20 November, the 1 clear morning in the preceding rainy period. On that day, where I live ISON rose at 0430 but needed until 0500 to get above the top of the surrounding jungle, and the sky started lightening up about 0515. Still, I easily found the thing with binoculars and, once I knew where to look, could even see it with the naked eye if I didn't look right at it (same as I do with M31). That's one of the benefits of living way out in the sticks :).

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MrChumley

MrChumley

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Comets don't even evaporate. They sublime. They're made out of ices (water, CO2, ammonia, ....) and rock (silicates, metals) and they turn directly to gas

Well, I think we can agree that what we are looking at coming out of perihelion is no longer made of "ice". So I think we can quit calling it an iceball. Also I find it discouraging how everyone "knows exactly what comets are made of"...With 90% of the universe comprised of "dark matter".

Anyways, you can still see ISON on LASCO C3, still there, still rebuilding it's tail... Sprouting it's wings again. /0\

(check page 1 I have been updating the latest LASCO image)

Foolish, or not....I'm still holding out hope for a decent show late Dec. :cool:

http://www.youtube.com/watch?v=fIQPkCR4E6k

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lajoswinkler

lajoswinkler

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Well, I think we can agree that what we are looking at coming out of perihelion is no longer made of "ice". So I think we can quit calling it an iceball. Also I find it discouraging how everyone "knows exactly what comets are made of"...With 90% of the universe comprised of "dark matter".

Anyways, you can still see ISON on LASCO C3, still there, still rebuilding it's tail... Sprouting it's wings again. /0\

(check page 1 I have been updating the latest LASCO image)

Foolish, or not....I'm still holding out hope for a decent show late Dec. :cool:

http://www.youtube.com/watch?v=fIQPkCR4E6k

It is completely possible that ISON's fragment still contains ices. The amount of heat needed to sublime a comet is incredible, and the only heat transfer here is radiative. Comet broke up because of pressure buildup and tidal forces, not because it has eroded completely.

The fragment still has a tail, therefore the ices are still there. Rocks can't form such tails.

Are you seriously implying that ISON is made out of dark matter? :huh: It's junk, a remnant from the early evolution of Solar system, rock contaminated with lots of ices.

I was really looking forward to see this comet for months, now. :/

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Designer225

Designer225

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Well, I think we can agree that what we are looking at coming out of perihelion is no longer made of "ice". So I think we can quit calling it an iceball. Also I find it discouraging how everyone "knows exactly what comets are made of"...With 90% of the universe comprised of "dark matter".

What if it returns? (Doubt ISON would return, but not Lovejoy.) Will you still call it an iceball? (We won't be living then... it's some 622 years into future...)

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Geschosskopf

Geschosskopf

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What if it returns? (Doubt ISON would return, but not Lovejoy.) Will you still call it an iceball? (We won't be living then... it's some 622 years into future...)

Hmm, I thought this thing was hyperbolic. But anyway, it's moot. ISON is kaput. What seems to have made it past the sun was just a handful of gravel flying in loose formation, which is now noticeably dispersing and fading out. Nothing to see here folks, move along :(

I recall last week that the Science Channel was advertising a show scheduled for 3 Dec called "ISON: Comet of the Century". I wonder if it will still air? :)

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K^2

K^2

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Hmm, I thought this thing was hyperbolic.

Yes, but only slightly, and only in the interior of the Solar system. In the outer Solar system, trajectory will become elliptic. This is due to interaction with other planets in the solar system, and actually pretty common for comets from Oort cloud. The simplest way to think about it is that it has enough energy to escape Sun's mass, but not the combined Solar System mass.

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Geschosskopf

Geschosskopf

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Hmm. My phone (Sky Safari app) has it's period listed as "infinite" and has since the get-go. And even had it survived, it was my understanding that it had been en route towards the sun for over 1 million years so had it survived, it would have had a period of about 2 million years.

Anyway, I'm totally bummed. I really didn't expect it to survive what with going through the corona, but I had hoped it would have been a better show on the way in. In the northern hemisphere, we haven't had a good naked-eye comet since Hale-Bopp or whatever it was 15-20 years ago.

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Brotoro

Brotoro

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Is there any chance that the break up of ISON would create a Perseids like meteor shower?

To get meteor showers, you need a short period comet to spread debris around its orbit. AND you need to have the Earth pass through the comet's orbit. So, no.

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Tommygun

Tommygun

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I was thinking maybe a one time event seeing that it was passing near Earth (about 60 million kilometers) and it might spread out that debris field a lot by then.

It might also be above or below the planetary plane by then too, so that won't help any.

Well just a thought.

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