Comet ISON Meets Comet Encke On Its Race To The Sun

Comet ISON and Encke “neck in neck” on Sunday Nov. 24 as seen by the STEREO-A spacecraft. Credit: NASA

Looking through photos taken in the past few days by NASA’s Solar Terrestrial Relations Observatory (STEREO) Comet ISON appears to be chasing Comet 2P/Encke as it dives toward the sun. You can watch their day-to-day progress by clicking HERE and selecting “HI Stars A” from the menu on the left side of your screen. Next, click on “1024 resolution” and then on a date link to see the image. It’s very cool to watch the comets’ changing positions even over the course of a day.

The two comets earlier today Nov. 25, 2013. Credit: NASA

Today ISON and Encke are stacked one atop the other. That’s line of sight only of course, since they’re actually separated by millions of miles. Encke passed perihelion, its closest point to the sun, on Nov. 21 at a distance of 30.7 million miles; ISON misses the sun by only 730,000 miles this Thursday.

Encke is an interesting comet in its own right. Discovered in 1786 by French astronomer Pierre Mechain, it was found in1819 to be a periodic or returning comet. Johann Encke first computed its orbit, which at 3.3 years, is the shortest verified orbital period known for a comet.

During the current swing-by, Encke showed up in the morning sky in August and remained visible through early November. The comet will be too near the sun to observe for the next few months as it fades from view. Farewell for another 3.3 years!

Keep a close eye on ISON. Word comes that production of certain molecules within the comet has dropped dramatically, which some astronomers are interpret as a sign that the icy core or nucleus of the comet is breaking up. Everything appears intact in the photos, but their resolution is not enough to reveal a breakup until large fragments begin streaming down the tail. We’ll have to wait and see.

Comet ISON’s location by the hour as it rounds the sun this Thursday. Created with Chris Marriott’s SkyMap program

I’ve written a guide for viewing Comet ISON on perihelion day when it will be brightest for the online publication Universe Today. Check it out if you like, otherwise I’ll provide an updated, condensed version here on the blog Wednesday.

7 Responses

  1. Edward M. Boll

    McNaught 2007 was the first comet I saw it in evening twilight. Will ISON be my first daylight comet? I hope so. And if or not, I will have my sights on Lovejoy that evening.

    1. Richard Keen

      Ed, my first comet was …. drum rolls, please ….
      Back in ’61, saw it with my 3-inch Edmund’s “Space Conqueror” scope, with the white carboard tube. It was as big a thrill as if it were ISON or Halley’s!
      I watched it with the same scope about 10 days ago. Looked about the same.
      Looks like the best show from ISON could be a few minutes after sunset Thanksgiving day. I’ll have to quickly run off to a scenic overlook for that, and scurry on back to make the gravy.

  2. Edward O'Reilly

    Hopefully,not a sign of imminent breakup.There have been reports of Ison’s impending death for a couple of months now but rumors of its death have been greatly exaggerated,to quote the poet.At least so far.Would be a bitter disappointment if Ison didn’t put on Some kind of a show,post perihelion.

  3. Mark Stevens

    My father took me out to the country with his telescope to see Haley’s on its last pass, but I cant remember what it looked like. Seeing Hale-bop in the sky was my first jaw dropping experience. I remember I was pulling out of my driveway to go to work when I seen it and my jaw dropped open. I took the day off and went out and bought myself a 5 inch telescope. It was a sight I will never forget. I hope Ison makes it and delivers me the same feelings Hale-Bop did

    1. astrobob

      Hi Mark,
      Thanks for your story. Just in case ISON doesn’t make it, we have a very nice comet in Lovejoy in the morning sky right now. It’s just visible with the naked eye and will look very nice in your 5-inch.

    1. astrobob

      Hi Brian,
      I would hold back judgement still. Ferrin has been known to make extreme predictions, so take what he writes with a grain of salt. While the comet appears to be in trouble, there has been a recent increase in dust production, though it might be for the wrong reason – breaking up of the nucleus.

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