Comet ISON Fades A Smidge, But Sit Tight, The Fun’s About To Begin

Comet ISON still looked wonderful in the camera on Nov. 17 when this photo was made. It’s proving a little tougher to see visually because of low altitude, dawn light and moonlight. Credit: Gerald Rhemann

Comet ISON snapped to life after the Nov. 14 outburst, but now appears to be waning a bit. I saw its remarkable transformation from a so-so comet on Nov. 13 to one with some real punch two mornings later.  By the 15th, the coma or head doubled in size and ISON’s tail shot out over 8 degrees – the distance your fist spans when held at arm’s length against the sky.

Comet ISON was taken with the TRAPPIST national telescope at ESO’s La Silla Observatory on the Friday morning Nov. 15, 2013 when it was at the height of its outburst. Credit: TRAPPIST/E. Jehin/ESO

Then everything stopped. More recent reports from Sunday and today show that the comet has faded some since the outburst, dropping from magnitude 5 to about 6. That’s a difference in brightness of 2 to 2 1/2 times. The tail has thinned as well.

In astronomy, the lower the magnitude number, the brighter the object, so this is not welcome news. A break or crack in ISON’s crust that exposed fresh ice to the sun’s heat was the likely cause of the recent outburst; while it’s almost certain to happen again, no one can predict when.

Couple the slight fade with low altitude, dawn light and bright moonlight and it’s no wonder even some seasoned amateur astronomers are having difficulty finding ISON in binoculars.

Processed images showing a possible jet extending southeast (PA 150 degrees) of Comet ISON’s nucleus as well as the new wing-like hoods on Nov. 17, 2013. The wings are dust from the nucleus pushed back toward the tail by the pressure of sunlight. Credit: Denis Buczynski and Nick James of the BAA

The good news is that the comet’s central core or nucleus still appears to be intact. We don’t want it to bust apart – not this soon anyway – or we’d be in for a poor show after perihelion (closest approach to the sun) on the 28th. Should the nucleus break up during or shortly after perihelion, the ice chunks would vaporize like crazy and create a spectacular tail with a small or even absent head.

There’s been discussion on the Comet ISON Observing Campaign website among some astronomers that the two wings of material now flaring inside the comet’s coma or head might be due to the breakup of the nucleus, but the jury’s still out.

Mark your calendar to watch for ISON’s appearance in SOHO images from Nov. 27 – 30. Click to be taken to SOHO’s coronagraph page. Credit: NASA/ESA

If the comet survives the intense 5000 degree solar roasting coming its way at perihelion, it should become showy enough to put a smile on the faces of those willing to stand out at dawn in December. In the meantime, you can use the maps from this blog to still track it yourself, or you can catch up on your sleep and wait until it enters the field of view of the Solar and Heliospheric Observatory (SOHO).

SOHO observes and photographs the sun 24/7 from a vantage point 1 million miles from Earth toward the sun. Onboard it has two of the coolest tools in the world for watching sungrazing comets like ISON. Called coronagraphs, they block or occult the sun’s brilliant disk making it possible for astronomers and regular types like you and me to study the sky near the sun.

Comet ISON enters the field of view of SOHO’s wide-field coronagraph early on Nov. 27 and departs late on the 30th. The comet should brighten dramatically during this time, so be sure to watch for it at this link. I’ll have continued ISON updates as developments warrant, so please stop by anytime. Questions? Just drop us a comment below.

13 Responses

  1. Norman Sanker

    Hey Bob,

    How about a brief outline of the best days to look for ISON in the daytime sky as it approaches (and recedes from) the sun and maybe a few tips on safety. I remember catching McNaught on a Sunday afternoon by sweeping with binoculars while Old Sol hid behind my swamp cooler and then realizing I could just b-a-r-e-l-y make it out naked eye as a tiny smudge. That’s my only daylight comet and I’d love to add ISON. Thanks for everything.

    Norman Sanker

    1. astrobob

      Hi Norman,
      I remember McNaught well. It was amazing to see it in the daytime through the scope. I’ll write up a guide for ISON as long as it gets bright enough at and around perihelion.

    2. Sean

      honestly Norman, the best knowledge seems to be that IF it were to get that bright it would only be on perihelion day, i.e. Thanksgiving (in the US), 11/28.

    1. astrobob

      Hi Jane,
      No, this is just part of the daily life of the solar system. Comets come and go all the time. Comet ISON is much too far from us – it’s nearly as far as the sun right now – to have any effect on Earth. Sit back and enjoy the show.

  2. Jane

    Thank you good to hear. More hupla involving earth being affected and government is what I’ve been told lol. U hear anything ?

    1. astrobob

      All that scare talk may have worked in the days of ancient Rome, but we know so much more now there is no reason to fear this comet or any of about a dozen other currently in the sky.

  3. Giorgio Rizzarelli

    We have rather clouds these days (now even rainy), but Saturday morning was clear and I got it.

    It was the most difficult session I had so far, with very strong wind, and only 10 minutes of dark from moonset to twilight, but I’m glad ISON was still in the outburst days.

    Needing to get on the near Carso upland as usual for mid-low light pollution, and in a point with clear horizon at East, the Bora wind coming from Siberia typical of North-East Italy was even stronger than in city, around 50Km/h and peaks of 70-80Km/h. It lets me think about the relativity of definition of habitable planet – a good “spacesuit” was essential. At my arrival the low Moon was still so bright that I didn’t need torchlight to mount the scope. Then as it set, I entered in maximum concentration to use the the few available minutes of dark, and when I finally saw the comet I almost forgot about the wind.

    In visual I saw it clearly in the 9×50 finder, while at 50x in the 200mm (8″) scope I was surprised I could (barely) see the green color. I saw the tail in both optics with averted vision. Photos in the scope at direct focus show very intense false nucleus, intense green coma and tail. The photo quality was strongly limited by the very high turbulence, so nothing compared to the marvelous pics around, but are a personal satisfaction.

    In same session I also saw comet R1 Lovejoy, which was also around mag5, with similar qualitative observing features to ISON.

    These days I also got the giant round sunspot AR1899. Thanx also scattered clouds, which make the air colder and still before getting the Sun in a hole in clouds, I saw very clearly the magnetic field lines on the penumbra (at 50×200). The spot was also visible with eclipse glasses, making a particular impression for being almost in center, like if one had pinched the Sun. I also got the sunspots in photos at sunset with landscape, without solar filter.

    1. astrobob

      A great read! Thank you for sharing that morning. And I agree, sometime we need to redefine what “habitable” planet means on such a wild morning.

  4. Edward M. Boll

    I was called into work. I looked at Spica with my own eyes about 80 minutes before sunrise.and thought I saw a faint shade. It was probably my imagination hoping to see something. No, for sure observation. I hope that tomorrow is clear. It will be my last chance until Saturday. It will be at perihelion before we know it. If the after show is anything like the so far before, it will leave many disappointed.

    1. astrobob

      You can use it to filter the sun but not the comet, since it will completely block the much dimmer comet from view. I suggest blocking the sun with a building or power pole and searching near the sun ONLY if the comet becomes unusually brilliant. Even then you’ll have to take great care not to accidentally look at the sun. The two will only be about 1 1/2 to 2 degrees apart at and near perihelion. I’ve looked at Venus – which is about as bright as ISON will get – and it’s extremely difficult even in a telescope to see it that close to the sun, much less the naked eye.

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