Comet ISON - Tail of the sky.

[peter]

Quick question re comet ISON, due to 'graze the Sun in late November - early December, with possibly spectacular effects visible to the naked eye as it passes through our region of the cosmos.

I have seen a 'schematic' of the commets positions 30 minutes after [before?] dawn on a number of days between the 1st and 17th of December as seen from the Northern Hemisphere. The commet appears low down on the horizon on or around the 1st December and over this period tracks higher into the sky untill it dissapears around the 17th.

[I have just answered my own question I think, but am going to persevere with this in case i) I am wrong or ii) you guys have anything to add]

My question [was going to be] "Why in the schematic, is the tail of the comet pointing forward [ie in the direction of its sucessive positions - that is up into the sky] rather than trailing out behind the comet like an exhaust plume behind a rocket. The answer is of course that it is. What we are seeing on each sucessive day as the commet 'climbs' higher above the horizon is just a change in our viewing position of the commet, that makes it look as though it is traveling in a direction with it's tail pointing out in front of it. In fact the tail is in reality dragging behind it relative to it's [the commets] motion, exactly as it should be.

As an aside - and not to add sensationalist content to an otherwise moribund post I asure you - I read recently how close that last commet that scorched across the russian sky back in spring was to actually causing a world changing event. A little bigger or a little closer and it would have been 'dinosaur time' for us! I think they said it was 17 miles above us in the atmosphere or there abouts when it exploded[could be wrong here] - certainly a close call.

[Fist and Faith]

I don't think the direction of the comet's motion has anything to do with the direction the tail points. I think it always points away from the sun.

[Vraith]

Quick question re comet ISON, due to 'graze the Sun in late November - early December, with possibly spectacular effects visible to the naked eye as it passes through our region of the cosmos.

I have seen a 'schematic' of the commets positions 30 minutes after [before?] dawn on a number of days between the 1st and 17th of December as seen from the Northern Hemisphere. The commet appears low down on the horizon on or around the 1st December and over this period tracks higher into the sky untill it dissapears around the 17th.

[I have just answered my own question I think, but am going to persevere with this in case i) I am wrong or ii) you guys have anything to add]

My question [was going to be] "Why in the schematic, is the tail of the comet pointing forward [ie in the direction of its sucessive positions - that is up into the sky] rather than trailing out behind the comet like an exhaust plume behind a rocket. The answer is of course that it is. What we are seeing on each sucessive day as the commet 'climbs' higher above the horizon is just a change in our viewing position of the commet, that makes it look as though it is traveling in a direction with it's tail pointing out in front of it. In fact the tail is in reality dragging behind it relative to it's [the commets] motion, exactly as it should be.

As an aside - and not to add sensationalist content to an otherwise moribund post I asure you - I read recently how close that last commet that scorched across the russian sky back in spring was to actually causing a world changing event. A little bigger or a little closer and it would have been 'dinosaur time' for us! I think they said it was 17 miles above us in the atmosphere or there abouts when it exploded[could be wrong here] - certainly a close call.

On the comet, you 1/2 answered yourself. The "Tail" can, and in fact often does, "trail" in front of the comet...and almost every other angle to its travel...[most comets have at least 2 tails, actually...and they only sometimes match each other exactly]
Visualize the sun and the comet from above, and the comet going counter-clockwise...say it starts, approaching from 12 o'clock...the tail will be behind it, at 12. As it circles to 9, the tail will point to the left, a right angle to travel. At 6, the tail will point straight "down"...but still at a right angle to its travel, cuz it is circling the sun. At 3 the tail is straight out to the right [and right angle], back at 12, the tail is straight up...in FRONT of the direction the comet, now moving away from sun [of course, the comet doesn't move in a perfect circle, and the section we're looking at would actually be more of a U-shape, entering, say, from 11, exiting at 1]
I'm fairly sure I recall it is POSSIBLE, when comet is moving away from sun, if conditions and composition are just right, that one tail...the dust particle tail, if the particles are large/heavy enough...will point behind [towards the sun] and the other[s] point ahead. The dust particles have to be heavy enough that the sun's gravity overcomes the solar wind blowing outward, [or at least slows them down enough relative to the speed of the comet core] but small enough to be blown away from the comet's core to begin with.

on the impact: it would have had to be a LOT bigger for a world-wide event. However, if you changed nothing else except it's angle of approach [in came in "flat"-ish, almost parallel to surface] to 60 or 90 degrees, it could have been much more impressive. If you changed the location, too, landed it on any city...it would have been bye-bye city...cuz I think the blast was 20 or 30 times bigger than Hiroshima bomb.

[peter]

That was an interesting lesson V. If I'm getting it, the common feature is that the tail is always pointing lengthways away from the sun and is independant of the direction of motion of the comets 'body' [in the normal manner at least and exepting situations such as you describe at the end]. One question - is the comet always describing an 'eliptical orbit around *our* sun with the sun being positioned at one of it's foci' - ie is it orbiting our sun, or is it [or indeed are there] 'wandering comets' that arrive from deep space, are slung-shot around the sun, and then escape from the suns gravitational pull and fly off into deep space again untill at some future time and in some future place, they are slung-shot around another sun, then another, then another etc. [I like the idea of this sort of billiard-ball rambling around the universe - hope it's true!].

[Vraith]

There is almost no doubt that some escape and in the fullness of infinity reach another system. The math shows there could be bodies orbiting us and our nearest neighbor...I think there are folk searching pics and data to find one.

[Hashi Lebwohl]

I read recently how close that last commet that scorched across the russian sky back in spring was to actually causing a world changing event

There have been reports of some Russian citizens showing the emergence of latent super powers since that comet's passing.

Not really, but that would be cool.

I need to see when/where Ison should be visible from our area. The kids need to see it--things like that are important.

[Vraith]

I read recently how close that last commet that scorched across the russian sky back in spring was to actually causing a world changing event

There have been reports of some Russian citizens showing the emergence of latent super powers since that comet's passing.

Not really, but that would be cool.

I need to see when/where Ison should be visible from our area. The kids need to see it--things like that are important.

wasn't that part of that show "heroes?

[peter]

I need to see when/where Ison should be visible from our area. The kids need to see it--things like that are important.[/color]

Will it not be visible in the whole Northern hemisphere on the same dates Hashi - ie 1st - 17th December? Agreed re the importance of seeing these rare phenomena; I saw Haley's Comet [not spectacular but historically significant], the total eclipse at the end of the millenia [just one of the most beautifull things I have ever seen] and the biggest lightening storm to hit Benares [Varanasee] in over a century [awesome beyond description] - these things both enrich your life and ground you in your small part of the cosmos simultaneously.

[Hashi Lebwohl]

wasn't that part of that show "heroes?

Part of Tim Kring's problem was that he never could settle on what actually gave people their abilities. He started off with a great idea then quickly painted himself into a corner from which he couldn't extricate himself. That, and the writer's strike that killed Season 2. Any modern explanation--comet, eclipse, mutation, etc--could never explain how the only white man in 16th-century Japan--a samurai, no less, if you can believe that--developed the ability to regenerate injuries and have a greatly extended lifespan.

Yes, peter, it should be visible during the same dates but I'll need to check on the visibility from my area. Too low on the horizon and it might be occluded by hills and trees.

[wayfriend]

I think I am reading that ISON may not be making it around the sun in tact.

Comet ISON Update: Will it Survive its Thursday Sun Bath?

Comet ISON is now only days away from our Sun, and it may not make it at this rate. NASA has announced that new data may show that the "comet of the century" could have started to break apart in a dramatic fashion. This means that we may not get the amazing light show in early December, though nothing is certain.

Currently, NASA is receiving reports that molecular emission from the comet has fallen dramatically. Meanwhile, the dust production seems to be enormous. This could potentially indicate that the nucleus of the comet has completely disrupted, releasing an enormous amount of dust while reducing emission rates. This means that the comet has essentially broken apart which, in turn, means that it likely won't be present in the skies in early December.

Too bad.

[Hashi Lebwohl]

If it doesn't disintegrate too much then we might get to see a swarm of cometlings...or whatever you call the small remnants of what used to be a comet.

[peter]

Come to think of it - a 'light-show' in December was bound to attract a certain type of 'millenarial exitement', so maybe it's for the best. I'll never forget those poor deluded souls who saw their redemption in the arrival of Hale Bop and their subsequent demise.