Comet ISON – what’s the big deal?

You MUST have heard by now that there’s going to be a brilliant, dazzling, blindingly bright comet in the sky at the end of next year. Woohoo!! The news is everywhere! Every space blogger is writing about it, every space journalist is writing about it, every astronomy forum is abuzz with discussion of it. It’s only a matter of time – hours, I reckon – before the Mass Media get a hold of the story (they’re currently focussing on newly discovered species of plankton), then it will go *nuts*…

< sound of screeching brakes >

Listen very carefully. I shall say zees only wance.


Got that? Good. Now, grab a coffee and we’ll chat about what’s actually going on, and what might actually happen.

I was going to write a long piece about this story for this blog, but in the end I wrote something for UNIVERSE TODAY instead. Go take a look at that, then come back, I have an interesting update. Go on, it’s ok, I’ll wait for you…

So, that’s the story. Basically:

* A comet has been discovered which will make a very, very close fly-by of the Sun next November.

* When it does that, it MIGHT become a very bright, possibly spectacularly bright, naked eye comet in our sky. Perhaps the brightest for centuries.

* But we don’t know yet what will happen. Comets are very unreliable and unpredictable, and this comet might yet fizzle out and be a let-down. We’ll have to wait and see.

What we do know – and this is all we know really – is where the comet will be in the sky, and therefore where it will be visible from. This time – and I’m sorry, I’m so, so sorry, but I’m feeling very “haha!!!” about this, which is unkind and ungentlemanly, I know, but after missing the last two Great Comets because I don’t live south of the equator I don’t care! – it will be observable from the northern hemisphere when it’s at its best.

I used the popular STARRY NIGHT astronomy software to leap forward in time to next November, to see where the comet will be. I almost fell off my chair when this appeared on the screen…

WHAT?!?!?!?!? Look at that tail!!!

< sound of screeching brakes again >

The problem with programs like STARRY NIGHT (which are fantastic, don’t get me wrong, that’s not a dig!) is that when it comes to showing the length of comet tails, they’re not to be trusted. They’re essentially software guesses. They don’t take into account the actual viewing geometry at the time, they just airbrush a long, straight tail behind the comet, pointing in roughly the right direction. So, as soon as it appeared (well, maybe a few seconds after!) I realised the depiction of the comet’s tail on that above image was NOT accurate, and when I posted that image, and other STARRY NIGHT renders, on Twitter I was very careful to tell people that.

So it was good to read a comment, and a warning note, from comet expert legend John Bortle on the forum where much of the discussion re the comet – Comet ISON – is taking place. Replying to another forum member who had, like me, used STARRY NIGHT to simulate the comet’s appearance next November he said:

Rahul, while planetarium programs are very helpful to observers in generating cometary ephemerides and plotting such objects’ positions among the stars, they can commonly get things wrong, sometimes very wrong, when attempting to predict the appearance of bright, small q, comets for some future date. Unfortunately, Starry Nights’ projections for the tail of 2012 S1 on the evening of 2013 November 29 are a classic example of this. Even if 2012 S1 fully lives up to its current hyped predictions, its appearance on the evening in question will be drastically different from the illustration posted on your site.

The tails of sungrazing and sun-skimming comets do not track around the Sun in an unchanging linear fashion. As folks will recall, the recent Comet Lovejoy completely lost its tail as it whirled arounded the Sun, thereafter growing a totally new one. Larger sungrazers more commonly will display torturously curved tails (both gas and dust) when passing through their perihelia. The same will surely to be true in the case of comet 2012 S1. The physical situation, one sometimes forgotten by even experienced observers, is that the gas and dust particles ejected from the comet’s nucleus require a finite time to recede from the nucleus to form the tails. The dust particles doing so at a much slower pace than the ionized gas. When the nucleus is traveling at enormous orbital velocity near the time of its perihelion passage, the tail particles are left behind forming a tight arc.

Thus, on the evening of 2013 November 29 the visual tail of comet 2012 S1 will likely be no more than a highly curved stump just a few degrees in length, no matter how brightly the comet’s head may shine. This situation will be compounded by the fact that whatever tail is present will be generally curving AWAY from Earth itself, not toward it.

Only as the comet recedes from the immediate vicinity of the Sun and it’s path through space becomes more linear will the new, long, and virtually straight tail begins to rapidly evolve. A really significantly long tail likely will not become apparent until at least a few days post-T. At the same time the history of tail development for past very bright sungrazing and sun-skimming comets indicates that maximum visual tail length usually occurs
when the nucleus is between 0.8 and 1.0 AU from the Sun if projection circumstances are reasonably favorable.

For comet 2012 S1 this should occur late in December with the comet circumpolar from higher Northern Hemisphere latitudes and with the comet’s nucleus nearest Earth. The waxing December moon will pose a problem in the evening sky from about the 7th until a few days past its full phase on December 22. I hesitate to make mention of the fact, recalling events surrounding Comet Cunningham in 1940 and Comet Kohoutek in 1973, but night of comet 2012 S1 most spectacular visual display could well be December 24th or 25th 2013.


Now that’s interesting! The tail might be at its most spectacular at Christmas! Where will the comet be in the sky at Christmas..?

Ooh, look at that… quite close to Polaris… and I think that it will be almost *circumpolar* as seen from the UK, which means it won’t set, or at least its head will only swoop behind the horizon for a while before reappearing again. Oh wow… if it develops a long tail we might see it shooting up from the horizon like Comet Lovejoy’s did recently…

And after midnight, when the comet was cimbing up into the northern sky again, it could look truly magnificent –


So… here we are… in the frankly fantastic position of having not one but *two* naked eye comets to look forward to next year, because don’t forget Comet PANSTARRS will be gracing our skies in March. Nine months after that, we might all be standing outside in our millions, gazing in awe at a Great Comet blazing in the sky, its tail sweeping across the heavens like a searchlight… or we might all be cursing ISON’s name and damning its memory like people damned Kohoutek’s memory back in 1974.

All we can do… everyone join in… is WAIT AND SEE… :-)

Now, go back to the top of the page and take a look at the charts…

122 Responses to “Comet ISON – what’s the big deal?”


  2. Well, a lot of those things they DON’T emit, your source material is wrong.

  3. If you’ve been to college and admire science you’ll know that spaceprobes have visited comets and taken measurements of their surface showing what they’re made of – ice and dust and frozen gases. You’ll also know that a probe fired a objective into a comet nucleus and analysed the debris plume, confirming their makeup. No ridiculous Electric Universe stuff with comets, just icebergs subliming in the light and heat of the Sun.

  4. You mean like this one?

    What if ISON was emitting energetic charged particles that interfered with the probes computer?

  5. Yes – 95% water. But please do not undersell the amazing mystery we are about to confirm (or reject) that Comets are the carriers of the seeds of life – especially hyperbolic comets like ISON coming from outside the Oort Cloud. I am betting that ALMA’s results will provide strong evidence that ISON contains the complex molecules of DNA. Free student material at :

  6. Apart from the fact that the probe you refer to was a long, long way from the comet, so if *it* had been affected by such an emission every *other* probe out there would have been too, how does a tiny piece of ice, mixed up with grit and dust, generate charged particles? Seriously, you need to do some research, and stop looking for woo woo explanations. The truth is amazing enough. :-)

  7. OK, here is my source material, I guess they are all wrong?

    You will also find that water is not measured directly from comets, they are an interpretation of the UV radiation emitted.
    Caltech Media Relations
    Earth’s water probably didn’t come from comets, Caltech researchers say

    PASADENA — A new Caltech study of comet Hale-Bopp suggests that comets DID NOT give Earth its water, buttressing other recent studies but contrary to the longstanding belief of many planetary scientists.

    In the March 18 issue of Nature, cosmochemist Geoff Blake and his team show that Hale-Bopp contains sizable amounts of “heavy water,” which contains a heavier isotope of hydrogen called deuterium.

    Thus, if Hale-Bopp is a typical comet, and if comets indeed gave Earth its water supply billions of years ago, then the oceans should have roughly the same amount of deuterium as comets. In fact, the oceans have significantly less.

  8. Phoenixpics,

    Thanks for asking about my blog. I am sure you are getting lots of interest with ISON’s big day(tomorrow) approaching. I have built up a pretty good following on my blog over the past year, I am getting 10-15 countries per day, about 100 visits. I have been researching the “vacuum” for a couple of years. My research is leading me to believe we have an energetic vacuum component in our atmosphere all of the time which is weakly ionizing and triggers a phenomena we call the “weather” which is really just our decaying quantum gravity field from the Sun interacting with our gaseous atmosphere and that the core of the Earth and Sun are possibly curled up 6-D or more toroids of vacuum energy per M Theory. We just live on the crust built up from their decay, like the crust of a comet. In fact my model says there is really not much difference between the Earth and a comet, just energy level and a comet may contain multiple, clumped nuclei. Think of plasmoids, found in comet tails as toroids of curled up decaying vacuum energy:

    I appreciate you posting information on ISON and other comets, NASA releases information in bits and pieces. What are the best websites to watch tomorrow?

  9. Because it is not ice, it is a Black P Brane from M Theory emitting charged energetic particles and decaying to protons (H+) creating the coma. They transmute matter along their surface through LENR (low energy nuclear reactions) and beta decay

    Example: Nuclei radius: 0.0001 meters
    Mass: 6.6x10e22 kg

    Their nuclei are part of the missing dark matter mass.

  10. Ahhhh…. Ok, I get it, this is a wind up… You almost had me going there! Who is this really? Nick? Simon? You guys…. ;-)

  11. I am interested in this hypothesis. BUT – I subscribe to the Water and “seeds of life” theory. I will follow your link and get back to you.

  12. I need to better understand your argument. I will read your references.

  13. I create the crop circles…:)
    I really do like your blog

  14. I also believe comets make water through low energy nuclear reactions and ionization. If they have a decaying vacuum core, they will transmute and ionize their surroundings along the firewall of their nucleus. In my model, a cometnucleus is made of the same energetic vacuum that is contained in our decaying quantum vacuum field expelled from the Sun in the solar wind, which ionizes oxygen, decays to H+ protons and makes and creates water vapor in our atmosphere.
    Thanks for following

  15. Dear ChemE : I noticed today the eccentricity dropped below 1. This means they are now betting it is on an elliptical path.;orb=0;cov=0;log=0;cad=1#cad

  16. I do not accept this argument. Although Hale-Bopp was a hyperbolic COMET and likely came through the Oort Cloud from another star, its angle of incidence is quite different from ISON so it likely came from another star. Over the life of earth, especially in its early formation, it would have taken many comets (from many different stars each with their own measures of deuterium) to deliver the quantity of water earth has. If you check my paper, I estimate 13 large comets (23 millions ISONs) the size of 95P/Chiron would deliver all our water. The chances are that each comet came inbound from a different star – so the isotope measure is not valid. Earth would measure an average of all these comets. Let’s wait just a few months until Antony Remijan delivers his paper on ALMA’s measures of ISON over the next 4 months. I bet he announces water – and many new complex molecules needed for DNA.

  17. Unfortunately the main paper you quote about water NOT coming to earth in Comets, was from 1999. NASA has made enormous progress in the last 14 years.

    1. The level of sophistication of our scientists’ study is well beyond most peoples vision or comprehension
    2. Water is already accepted as the pre-dominant “non organic volatile”
    3. Extensive experiments on 14 previous COMETS will be continued on ISON
    4. A “taxonomy” (ie classification system) is evolving for Comets.
    5. Finding “life” in Comets continues to be a challenge until NASA defines what are the biomarkers for life – expect paper in 2014 by NASA astrobiologist Chris McKay. Focus will continue to be looking for complex molecules required in DNA.
    Good summary here :

    Points to excellent August 2012 seminar (video) where all the key astronomers planning the massive observation of ISON got together in a 2 day planning session.

  18. Thanks,

    I think the nuclei are energetic, which is why they can change path and why a coronal mass ejection can accelerate as it is leaving the Sun.

  19. So I believe what we might be seeing is the moment of capture (by the sun) of a hyperbolic comet from another star. Cool or what? (e is now .9999977109551715 with newly calculated orbit time of 400,864 years). I guess I will not be around to celebrate its return :-)

  20. I made an error here. ISON’s orbit goes through continual change as it first passes planets (esp Jupiter) and then as it takes the pressure of heat, gravity and solar wind close into the sun. The JPL orbit measures did fall and remain under 1.00 (ie elliptical). But the error margin makes this just as likely it is 1.00 – (ie a parabolic trajectory).

  21. How’s your blog coming on?

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