Comet ISON Update Nov. 30 – This Is How The Cookie Crumbles

Comet ISON is little more than an expanding dust cloud as it heads away from the sun this morning. SOHO image. Click to see a video of the past 3 days of ISON’s travels around the sun. Credit: NASA/ESA

Yes, the comet’s still there, but it’s been transformed into a blizzard of dust. Our hopes for a bright comet at Christmas appear to have gone up in smoke. Or have they?

Space-based cameras show an expanding dust cloud with two tails. According to Hermann Böhnhardt from the Max Planck Institute for Solar System Research, the tail pointing back at the sun is made of dust particles shed before the comet made its close brush with the sun Thursday, while the other is more recent dust vaporized from whatever was left of ISON’s nucleus during perihelion passage.

Comet ISON photographed in the COR2-B coronagraph from NASA’s STEREO-B solar probe on Nov. 29. Jupiter is left of the sun. Credit: NASA

The solid nucleus, estimated at 1.5 mile-wide (3 km) across, once provided a steady supply of vaporizing dust and gas. It’s now crumbled to pieces, and those pieces are vaporizing away in the sun’s to create an expanding cloud that’s fading by the hour.

Another view of the comet in the COR2-A coronagraph on the STEREO-A sun probe on Nov. 29. Venus is left of the sun. Credit: NASA

This morning ISON glows around magnitude 5, making a naked eye sighting increasingly unlikely in the coming days. There’s still a remote chance the comet’s engine will fire up again like Comet C/1962 C1 Seki-Lines did in April 1962. During perihelion, Seki-Lines was expected to brighten to -7 magnitude but instead it totally dropped off the map only to reappear a few days later as bright as Jupiter. Could ISON do the same?

Should ISON continue to fade as expected, it may take a fair-sized telescope to see it in the morning sky. We’ll have to wait longer to make the attempt because a dark sky will be needed to see a low-contrast object like a “cloud”. ISON will appear in a dark sky – but very low – around Dec. 7.

You might wonder if the rocks and dust in the expanding cloud have any chance of producing a meteor shower or worse, pose a threat to Earth. The answer is no. Whatever is left of the comet will continue following the same orbit it’s been following and will not come near the planet. ISON’s ghost will pass a very safe 39 million miles from Earth on Dec. 26.

I like to picture whatever chunks of ice are left over as unexploded ordinance. Maybe, just maybe, there will be a temporary re-brightening as fresh surfaces get pounded by sunlight and vaporize, but given ISON’s talent for defying predictions, we shouldn’t count on it. Still, the comet may have other tricks up its sleeve. Let’s watch and wait.

16 Responses

  1. Edward O'Reilly

    Very disappointing news for all of us.Hopefully,Ison will continue to pull rabbits out of its hat but,as you say,it’s looking increasingly unlikely. What I find amazing,Bob,is the size of its pre-perihelion nucleus.At 3 km,this core should have been more than sufficiently large to withstand the stress of its close passage.Other smaller comets have passed even closer and survived.Perhaps Ison was rather poorly constructed?Hard to say.Given the hoopla,if it doesn’t even appear post-perihelion,I’m afraid Ison may be permanently remembered as a ‘dud’ comet.Is a real shame.

    1. astrobob

      The 3km is an estimate only – I still haven’t heard of a definitive size. ISON may have been rubble-pile cemented by ice into a single body that ultimately fell apart fell apart during perihelion stresses.

      1. The HiRISE camera on the MRO could set a pretty firm upper limit for the nucleus diameter of only 1.2 km – this came out only on the morning of perihelion day; had we known earlier that the nucleus was that mall, expectations for its survival and a great show afterwards would have been lowered long ago …

  2. Edward O'Reilly

    Perhaps a hodge-podge of a comet? Pity we can’t discern their internal structure more accurately-we’d then be able to separate the ‘men from the boys’,so to speak.But they’re so small and so far away,it is understandably difficult.Is still a small chance to see something. I’ll still give it a shot,starting Dec1-2

  3. Hi Bob,

    Good Afternoon to you over there !! Yes, it looks ISON is slowly fading away with whatever that’s left of it. Out of curiosity, I download the latest SOHO pic of Ison ( 15.54 ), Crop, enlarge it, convert it into Negatives and then to Grayscale. Then do a Luminance Noise reduction and to my Surprise, I saw four Lumps of loose Materials ( Nucleus ? ). Well, maybe its just background Artifacts of distant stars, but i do feel there’s something there. I know it won’t be a naked eye comet this dedember, but something is better then none.

    Would like to post it here, but couldn’t find a link. Can I have your email, so that i can send my Photo to you ? Thats if its O.K. with you.

    Thanks again … James Moh.

    My email :

  4. Jaye Squire

    All things being equal, which they never are with visiting objects in our galaxy, ISON should have been able to survive perihelion.

    I am wondering if the US and/or Russia were involved in some target practice with our buddy ISON in preparation for future objects that could eventually enter our neighborhood and injure our beautiful planet.

    And why would NASA tell no one? All one has to do is look at all the hysteric chatter accompanying ISON’s presence in our solar system – and the previous suicides that have occurred with other comets and asteroids. Were we to have missed, no amount of data would have convinced anyone that ISON was not a danger.

    Personally, I hope there is some “practicing” going on. And where better to intercept a comet than its immediate proximity to the sun … where there would be the best chance of fragments vaporizing, and breaking a part at high velocities.

    An substantiated hunch … or, really good fodder for a movie.

    Jaye Squire

    1. astrobob

      * The very fact that ISON broke up shows that all things are not equal. Comets passing so close to the sun frequently vaporize, though most are small and don’t get the attention that ISON did.
      * You may muse about target practice, but no missions of any kind were planned or even could have been planned to Comet ISON given the short time frame between discovery and perihelion. Not to mention the great difficulty in building and shielding a craft that would pass so close to the sun.
      * There has always been hysteric chatter accompanying any potentially bright comet, especially in our era when the Internet is filled with gift-wrapped pseudo-science and conjecture.
      * NASA has been unbelievably forthcoming in sharing the data from space telescope and ground resources.
      * “Good fodder for a movie” — now that’s something we both can agree on!

      1. Jaye Squire

        Ah ha! Guess I shall start the screen play then …

        I disagree with your statement about NASA’s “forthcomingness,” because I have been through hurricanes, and understand the millions of dollars, unnecessary loss of jobs, and panic that can ensue with incorrect descriptive statements, or factual disclosures.

        NASA employees have to be mindful of virtually every word they publish, and how they describe any given endeavor. They well understand how their announcements and observations can be misinterpreted, or cause widespread panic.

        I have a NASA bud 😉

        And thank you for the feedback.

        1. astrobob

          You do have a good point. Given NASA’s status/position, they have to be especially mindful of being misinterpreted. Thanks for your perspective.

  5. Hi Bob,
    Got to admit, after a few Photoshop tweaks, still could not see the Fragments or whats left of it. Ison Died Twice, just as the James Bond movie …” You only Live Twice ” ..Ha,Ha. But it was a Thriller all the way !! Now for that ” Green ” cat called ” Lovejoy ”. Thanks again for everything !!

    Cheers !! …. James Moh.

  6. Robin M.

    I have no scientific background and thus, had hoped that the reason I was seeing the imagery growing dimmer and dimmer was due to – oh, maybe because the body was moving out of range from THIS particular satellite’s view? (please?) NOT because Comet Ison was fading; dying YET AGAIN. No…, not after 14 months of excitement and anticipation (please?). I don’t own a telescope, though I hope to change that soon. I live in an urban environment but – undaunted, I immensely enjoy meteor showers in my backyard or bundled up in blankets on a recliner in the driveway because it’s impractical for me to be elsewhere. Even when the temps are well below freezing…. January’s Quadrantids in New England…? Sure! No pesky mosquitoes, either : )
    I saw an Aurora from my front sidewalk in 2003, albeit, it was rather weak. I love sky-watching on starry nights or when skies get stormy… or just observing cloud formations.
    Ison was to be “my” second comet, and the first since Hale-Bopp, which was mesmerizing. I absolutely couldn’t wait for Ison : (
    Now, THE month is upon us when magical, unforgettable sights were going to be OURS, just for the price of looking up …. Will it be? No, wait -Yes, or maybeeee, oh, no…. it is plop-plop, fizzle-fizzle, fade-fade, bye-bye. I so believed otherwise, Ison!
    Yes, I know that these celestial events aren’t sure bets. Still, I am profoundly sad and I have to be honest – I was SO emotionally invested in Comet Ison and I’m somewhat devastated. If that sounds over the top, so what. If THIS isn’t the place to admit the way Ison affected me, then nowhere is!
    I know how awestruck I felt seeing Hale-Bopp in the sky; night after night for many weeks and from what I gathered… Ison had the potential; the ingredients, and the hype to be even better.
    Then I started seeing some terrific pictures people took recently, as Ison approached Perihelion. I was not able to partake in the excitement just YET. But, “SOON”, I thought – it would be visible. I was going to borrow my daughter’s digital s.l.r. Nikon camera, and take photographs of Comet Ison. All I needed were small, affordable items like a tripod and an attachment to click the shutter without shaking the camera. Oh, well. : (
    Sorry to come off like this big baby but I hoped and prayed for it to happen. So many young people would have developed a lifelong appreciation if the comet had been visible.
    I found out about a scheduled event at a nearby Observatory affiliated with Harvard U. on Dec. the 14th at 5 a.m. in conjunction with Ison. It would’ve been so cool. I’d never been to anything like that. It coincides, or would have coincided with the Geminids meteor shower’s peak (after the moon sets, too) but I trust they’re calling THAT puppy off NOW : (
    I will end this rant on a positive note believe it or not – This same observatory is holding a seminar on telescopes, 12/19 – in just a couple of weeks. I plan to learn more about what telescope will best fit my purposes within a price range that fits my budget.
    While I am heartbroken that in the end, Ison did not come out and shine for me, and for us – I will make a new game plan for what comes next! If the next big thing won’t come to me, I will learn which telescope I can obtain to “go out to meet it” somewhere in space. Yes! In addition, we have a huge swaths of totality in the U.S. and Mexico that are luckily going to have 2 solar eclipses in the next decade or thereabouts. The first of which is in 2017…. not too far off! Here’s wishing you all the best from metro-Boston!

    1. astrobob

      Dear Robin,
      Thank you for sharing your feelings and reflections about Comet ISON. Happy to see your enthusiasm remains undaunted, and I hope you find the right scope. Rest assured, much will come your way, and you won’t have to wait till 2017. There are two total lunar eclipses in 2014 and plenty more comets on the way. There’s even a very nice one out now visible in binoculars (away from the city) called Lovejoy. Try to see it if you can. As for those Geminids, even if the observatory calls the event off, they’re still worth your while.
      But back to ISON. Even if it didn’t perform as hoped, we got to watch it from start to finish (if it IS finished) and saw amazing and surprising behaviors. I think there will be much new science learned from Comet ISON that will be published and discussed in the months to come.

  7. Raymond R.

    : ( Seems like ISON has finally run out of tricks… But at least it became the 3rd-brightest comet of the century despite not being widely seen, and (possibly, counting NEAT and PanSTARRS) the 5th comet this century to reach negative magnitudes. I certainly hope it won’t be remembered as a dud; it was certainly the most unpredictable and entertaining comet I have observed, right until its bitter end. : )

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