Is Comet ISON Just “Mostly Dead”?

Comet ISON early this morning Nov. 26 alongside Comet Encke as seen by STEREO-A. Credit: NASA

Is Comet ISON dying or thriving? There’s much discussion today among amateur and professional astronomers about a decline in its water and dust output and the comet’s reluctance to brighten significantly so close to the sun. I wonder what Miracle Max would have to say?

In one of my favorite movies, “The Princess Bride“, the character Miracle Max (played by Billy Crystal) examines an apparently dead man his friends hope he can bring back to life. Says Max:

“It just so happens that your friend here is only MOSTLY dead. There’s a big difference between mostly dead and all dead. Mostly dead is slightly alive. With all dead, well, with all dead there’s usually only one thing you can do.

Friend: “What’s that?

“Go through his clothes and look for loose change. ”

So maybe ISON is only mostly dead, which as Max points out, is very different from all dead. Like any comet approaching the sun so closely, ISON faces many obstacles: powerful particle winds and solar flares that can shred its tail and rattle the nucleus, tremendous heat and gravitational stress. What a poor 3-kilometer fluffy ball of ice and dust to do? Yes, it might be broken, but even if true, we could still see a spectacular tail after perihelion.

Photo of ISON today Nov. 26, 2013 taken by the Cor-B coronagraph on the STEREO Behind spacecraft, the twin of STEREO A. The sun – white circle – is hidden behind a metal disk in an instrument called a coronagraph. Credit: NASA

Pictures taken today by NASA’s STEREO Ahead space probe still show a bright comet head and longish tail. If the nucleus or comet core is cracking up these images are still too low a resolution to tell. On any old day, you wouldn’t know a crisis was brewing.

Now that the comet is too near the sun to see visually the only way we can study it from the ground in the coming days are with radio-dish-style telescopes sensitive to a slice of light between infrared and radio called the submillimeter range. This is where all the bad news is coming from.

Astronomers using the IRAM (Institute for Radio Astronomy in the Millimeter Range) telescope in Spain and James Clerk Maxwell Telescope in Mauna Kea, Hawaii report rapid fading of molecular emission lines (light given off by sunlight-excited molecules sputtering off the nucleus) by a factor of 20 or more. This may indicate that the nucleus is now at best marginally active or that it no longer exists.

Comets ISON and Encke today in STEREO-A. I’ve cropped and enlarged the comets so you can better see the second tail streaming away from ISON. This may be fresh dust from a breakup of part of the comet’s nucleus. Credit: NASA

Them’s fightin’ words. I’m going to remain guardedly optimistic about ISON’s fate and hope for a little loose change. You can track the comet’s progress through the STEREO spacecraft’s eyes by following the link and instructions in yesterday’s blog. Here are some other great resources:

Comet ISON pokes its head for the first time into the coronagraph of the Solar and Heliospheric Observatory (SOHO) late on Nov. 26 CST. What appears to be a coronal mass ejection is spreading away from the sun. Credit: NASA/ESA

* Join NASA’s Fire vs. ISON Google+ Hangout LIVE Thursday Nov. 28 from noon-2:30 p.m. CST during perhelion. Listen to and ask questions of professional astronomers and scientist and fab blogger dude Phil Plait.

* Solar Dynamics Observatory views Comet ISON on Nov. 28. This website will display near real-time images and movies of the comet. Images should begin appearing sometime between 11:45 pm and noon CST. The solar space telescope will be specially offset from the sun to shoot the photos.

* Make your own ISON movie using near real-time photos at STEREO/Secchi site. Select the telescope (HI1is or COR-1), click Secchi A for observatory and then punch in the date.

*** Latest update: The International Astronomical Union’s Minor Planet Center has just issued an updated predictions for Comet ISON.  A maximum brightness of about first magnitude is forecast at perihelion with the comet entering the morning sky in early December no brighter than magnitude 3.5.


18 Responses

  1. Brian Larmay

    Hilarious… I just watched this movie last weekend and thought the EXACT same thing about ison this week.
    The suspense behind this comet is intense to say the least, especially with ison in the red zone now. All eyes are on ison!

    As of today, Matthew Knight from

    Kitt Peak still sees a steady increase in brightness in the last 5 hrs.

  2. Edward M. Boll

    When discovered I was thinking magnitude -20. Now, I know that is almost impossible. It was estimated at magnitude 3 the other day This really is not much dimmer, only 1-1.5 magnitudes dimmer than I had figured since perihelion. People may think my prediction of a magnitude of -15 now is crazy at the minute of perihelion. Believe me if it gets nearly that bright, it will start dropping off fast afterward. Maybe my prediction is way off, but I would be very pleased if I and others as optimistic as I had the last laugh on this one.

  3. Dana

    I still don’t think it’s made of ice and dust , neither does many experts . But keep putting that out there with no true evidence, it’s ok. To the contrary although, there has been probes sent to comets and exploded to analyze the data from those explosions and the findings were conclusive. Not made of ice.

    1. astrobob

      We’ve analyzed them from near – with spacecraft – and far and there’s no doubt comets are primarily ice (mostly water). What do you suggest they’re composed of?

  4. Edward O'Reilly

    Hello, Bob. As a followup,Karl Battams and Matthew Knight have just posted on the CIOC site that Ison has resumed brightening during the day on Tuesday(Nov26),after dimming during Nov25.According to them,they are ‘significantly less fearful that it has fully disrupted’ and that ‘there is a significant chance that an appreciable chunk of nucleus still exists’. Great news after the admittedly depressing scenarios of yesterday! In fact,in today’s news conference,NASA suggests that Ison’s post perihelion performance may be reminiscent of Comet Lovejoy of 2011-12!.THAT would be something worth waiting for.Fingers crossed as it’s just about ‘crunch time’.

  5. Edward O'Reilly

    Yes,was admittedly worried about the reports of a possible breakup that were circulating last couple of days.If nothing else,Ison has shown itself to be a resilient little fighter that won’t go down easily.Am intrigued by NASA’s comparisons to 2011’s Lovejoy.Its nucleus DID ultimately fragment but it still put on a beautiful show in southern hemisphere. Perhaps,with Ison,it’s our turn?

    1. astrobob

      I’m going to try for it today with binoculars though I don’t think it’s much brighter than 1st magnitude. Should be challenging.

  6. Edward O'Reilly

    I know peak mag estimates are all over the place(understandable given the comet’s behaviour the past 2 days) but do you think it’s now pretty certain that Ison won’t be a daylight visible comet?

    1. astrobob

      It seems anything is possible. It appears to be roughly as bright as Antares right now and we’re still a day before perihelion. I’m guessing it will become visible in daylight but possibly only through a telescope. I’ve seen Mercury at -1 without difficulty in daylight through the scope by offsetting from the sun. Unfortunately it will be cloudy here tomorrow.

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