A Comparison Between Comets ISON and Lovejoy (2011)

November 29th, 2013 by Roy W. Spencer, Ph. D.

The experts are still trying to figure out just how much of Comet ISON has survived during Comet ISON’s flyby of the sun yesterday.

I’m not a comet expert, but I’m going to venture a guess based upon the following comparison to another comet (Lovejoy) that also surprised astronomers when it survived perihelion in December, 2011.

Here’s a time lapse video of imagery from the SOHO LASCO C3 instrument when Lovejoy flew around the sun on 16 December 2011. Note three things:

(1) the horizontal flaring (sensor overdriving), which indicates a very bright object, both before and after perihelion;
(2) how compact the comet nucleus remains after perihelion,
(3) how the comet gradually grows a new tail pointing away from the sun after perihelion.

Now let’s look at Comet ISON. Compared to Comet Lovejoy, note:

(1) there is not as much flaring before perihelion, and NO flaring (yet) after perihelion (ISON is not as bright as Lovejoy),
(2) the nucleus is much more diffuse (larger, but dimmer) after perihelion,
(3) there appears to be comet material “flung outward” after perihelion, even before a new tail grows.

Now for some wild speculation by a rank amateur. I think the nucleus mostly broke up during perihelion, and what we now see is diffuse material that will rapidly dim in brightness over the coming days and weeks. I hope I’m wrong, of course…I would love to do more time lapse video of a brilliant pre-dawn comet. But at this point, I’m not hopeful.

14 Responses to “A Comparison Between Comets ISON and Lovejoy (2011)”

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  1. Mac says:

    Love this stuff, what sort of speed would a comet like that have as it passed the sun, any ideas?

  2. Hans Erren says:


    Hi, I blended the LASCO image into an image of the Scorpius constellation I made myself in 2005 in Arizona. This gives you a good impression of the current comet magnitude, I estimate 0 to -1

  3. Svend Ferdinandsen says:

    350 km/s is the estimate i have seen, and it seems to be a good guess according to the supposed trace.

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  8. Denver says:

    Will note how the comet gradually grows a new tail pointing away from the sun after perihelion.
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  9. Davidson says:

    I’ve watched the two videos and I can say that comet ISON is spectacular.

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