A Novice Observer’s Guide to Comet ISON

By Corey S. Powell | October 25, 2013 2:35 pm

If you enjoy a dramatic spectacle in the sky, you have probably heard about Comet ISON, currently streaking toward the sun. (If you haven’t heard about it, bear with me—I’ll try to make it worth your while.) But the media coverage has been downright confusing. The first reports described it as a “comet of the century,” possibly as bright as the full moon. Then came some whipsaw downbeat news stories suggesting that the comet was fizzling and might have already begun to disintegrate.

Comet ISON as seen by the Hubble telescope on October 9, when it was 177 million miles from Earth. (Credit: NASA/ ESA/Hubble Heritage Team)

Comet ISON as seen by the Hubble telescope on October 9, when it was 177 million miles from Earth. (Credit: NASA/ ESA/Hubble Heritage Team)

No wonder DISCOVER readers have been sending in a steady stream of inquiries: What will Comet ISON really look like? When will it be visible? Where can I see it? Good questions. Time for some answers—and I’ll have a lot more to say about the science of the comet itself in an upcoming blog post.

What it will look like Almost all of the forecasts about Comet ISON contain huge uncertainties. As comet hunter David H. Levy is fond of saying, “Comets are like cats; they have tails and they do precisely what they want.” The Comet ISON Observing Campaign has put together a set of scenarios that explore the staggering range of possibilities.

It now seems almost certain that Comet ISON will fall short of the early, optimistic assessments (truth be told, it was never going to light up the night like the full moon, since peak brightness will happen while it is less than one degree from the sun…in the middle of the day). The dire predictions that the comet has fizzled are simply wrong, however. Recent Hubble images show it beautifully intact.

A recent study by Jian-Yang Li of the Planetary Science Institute gives additional reason for hope. Comet ISON is oriented such that one side has remained shadowed so far. When the comet whips around the sun on November 28, the comet’s night side will suddenly emerge into daylight and be hit with an intense blast of solar heat. That could potentially lead to a spectacular eruption of gas and dust.

The upshot is that Comet ISON is sure to be a pretty sight through binoculars or a wide-field telescope, and it still has plenty of potential to be an exciting addition to the visible sky after Thanksgiving.

When and where to look I created a quick reference guide about when and where to look for Comet ISON. It appears in my Urban Skygazer column in the November issue of DISCOVER, and you can read it here. A viewing skychart is available from my colleagues at Astronomy magazine.

There are two crucial things to know about looking for Comet ISON.

Projected brightness of Comet ISON (with actual measurements in orange) shows how it will peak very rapidly at closest approach to the sun on November 3. (Credit: Credit: NASA CIOC/Matthew Knight)

Projected brightness of Comet ISON, with actual measurements in orange, shows how rapidly it will peak at closest approach to the sun on November 3. (Credit: NASA CIOC/Matthew Knight)

First, it is a peaky comet (full details here if you want to take a deep dive). It will brighten rapidly in the days just before Thanksgiving, so don’t even try looking for it with your naked eyes right now—it’s far too faint. Probably it will become visible from dark skies by mid-November, but may be tricky to see on its way in. The best viewing should come in the couple weeks after November 28, when the comet is heading away from the sun but toward the Earth. Because of the shifting geometry, Comet ISON will probably fade quite a bit more slowly than it brightened. Even so it may be lost to the naked eye well before it makes its closest approach to Earth on Christmas day.

Second, you will need dark skies and an unobstructed horizon to get the best view. At its brightest, Comet ISON will be close to the sun and hence close to the horizon just before sunrise. In the first half of December the comet will get higher in the sky and (depending on how it behaves) may have a ghostly tail stretching up to a quarter the way across the sky. To appreciate its full extent, though, you will need to get far away from urban light pollution. And as you may have already picked up, you need to wake up early in the morning, just as dawn is breaking.

OK, so will it be worth the effort? Nature doesn’t always make things easy or convenient. The payoff is that you will get to see something rare and wonderful: A primeval ball of ices and dust grains, frozen since the time of Earth’s formation 4.5 billion years ago, vaporizing and spreading out into space. It’s also amazing to recall how small the actual  comet is. Its tail may stretch millions or even tens of millions of miles across, but the solid body creating that whole spectacle is just a couple miles across!

If you get an exceptionally good look at Comet ISON’s tail you may be able to see that comets actually sprout two kinds of tail–an ion tail (composed of individual, electrically charged gas atoms) and a dust tail (composed of larger particles). Both tails are affected by both the solar wind and by light pressure from the sun, but they react in different ways. The ion tail always points straight away from the sun. The dust tail lags behind a bit as the comet orbits around the sun. The result is that the two tails typically show up separately, often with distinctive structures,  shapes, and colors.

So when you view a comet you get to see the invisible interplanetary dynamics of the solar system, as well as a relic from a time when Earth was just a lifeless ball of molten rock. Worth getting up early for, I think.

Follow me on Twitter: @coreyspowell

MORE ABOUT: comet, Comet ISON, skygazer
  • James Boss

    Find great deals on magazine subscriptions. To learn about
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  • http://www.parajuego.com/ Para juego

    that meteorites? or just a comet? real mystery! the universe is probably discover the mysteries of space, which is what I would expect

  • Michal Sadlon

    if you want to follow how comet ISON is going through Solar System,
    take a look at this real-time simulation

    • coreyspowell

      Very cool, thank you.

    • jessica cozadd

      am i the only one who notices that when ison comes close to the sun, EARTH actually stops moving for a few seconds on this website???? Or does no one care to notice it?

      • Michal Sadlon

        Hi Jessica,

        we are significantly reducing speed of playing time, when comet is near the Sun, so it looks that Earth and other planets stop.
        When we played time equally, ISON was too fast to notice what´s going on. Regards.

  • Guest

    COMETS, AND METEORS ORIGINATED FROM EARTH: In the Earth’s past there were
    powerful volcanic explosions propelling millions of tons of earth soil and rock
    (now asteroids and meteors which may contain organic molecules or organisms)
    into space. Read my popular Internet article, ANY LIFE ON MARS CAME FROM EARTH.
    The article explains how millions of tons of Earth soil may exist on Mars, and
    how debris we call asteroids and meteors could have originated from Earth.
    According to a Newsweek article of September 21, 1998, p. 12 that quotes
    a NASA scientist, SEVEN MILLION tons of Earth soil may exist on Mars! How could
    this be possible? Read and find out.

    Even if the right chemicals exist, life cannot arise by chance. The
    molecules that make-up life have to be in a sequence, just like the letters
    found in a sentence.

    Scientist and creationist, Brian Thomas explains:

    measure comets’ masses and erosion rates to calculate potential lifespans.
    Sungrazing comets last fewer than 100,000 years.2 They thus confront
    secular astronomy which maintains that comets formed with the rest of the solar
    system billions of years ago. A solar system that old should have no remaining

    How do secularists solve this dilemma?

    Reporting on Ison, The Independent said, “Comet Ison has taken
    millions of years to reach us travelling from the so-called Oort cloud – a
    reservoir of trillions and trillions of chunks of rock and ice, leftovers from
    the birth of the planets.”3

    Unfortunately, nobody has yet witnessed a single one of those
    “trillions and trillions of chunks.” Going strictly with
    observational science, the “so-called Oort cloud” may exist only in
    the reservoir of the human mind.

    Clearly, secular astronomers invented the Oort cloud to rescue their
    billions-of-years dogma from a disintegration process that limits a comet’s
    age—and thus the age of the Solar System—to thousands of years. When Ison
    becomes visible later this year, perhaps it will remind thoughtful viewers that
    the universe is quite young, just as Scripture teaches” (Brian Thomas, M.S., Science
    Writer at the Institute for Creation research).

    Check out my most recent Internet articles and sites: THE SCIENCE

    Babu G. Ranganathan*

    B.A. Bible/Biology

    Author of popular Internet article, TRADITIONAL DOCTRINE OF HELL EVOLVED

    *I have given successful lectures (with question and answer period
    afterwards) defending creation before evolutionist science faculty and students
    at various colleges and universities. I’ve been privileged to be recognized in
    the 24th edition of Marquis “Who’s Who in The East” for my writings
    on religion and science.

    • xfsdf

      What a wanker

    • bwana

      In his own little world…

    • coreyspowell

      I don’t believe in censoring reader comments unless they are offensive or inappropriate. Instead I take this uninformed, anti-scientific post as an opportunity to encourage readers to explore the real science of comets, described in depth in my cover story in the November issue of Discover:


    • NueeArdente

      Interesting fiction. I think I will stick with Harry Potter and the Lord of the Rings though. Far more interesting.

  • Ba lee

    Author probably still believes in dirty snowballs

  • G Leveson

    For those that have iPads, Luminos has a very nice app that synchs with wifi telescopes and also has detailed information about ISON. The app allows you to look forward and backward in time (hrs, mins, days) so you can see when ISON is best to watch.

    Its current magnitude (as up today) is 8.10 mag. In comparison PANSTARRS was about 2.5 to 3.5 mag when I capture it in March 2013. Jupiter these days has a magnitude of –2.23 mag (defined as extremely bright- visible at naked eye). Mars is magnitude 1.49. Arcturus one of the brightest stars (visible at naked eye) is –0.1 mag and Capella is 0.1 mag

    On Nov 3rd, ISON magnitude would be 7.53 mag, only visible with telescope (worst than Mars) The comet will be on its way to the SUN and no body knows if the comet is going to survive


    – On Nov 27th, ISON magnitude would be 4.23 mag, (fainter than PANSTARRS but visible with telescopes)

    – On Nov 28th, ISON magnitude at Dawn and at the southeast is going to be –5.07 mag (visible at naked eye), but it will be close to the sun at Dawn. And mag –6.43 at sunset (6:32 p.m. PST) and the sun will be below the horizon.

    – On Nov 29th, ISON magnitude is going to be –1.13 mag (visible at naked eye and as bright as Arcturus). It will be visible at down to the southeast at 6:20 a.m. PST, the sun will still be down the horizon till 6:40 a.m., ( we can enjoy ISON for about 20 minutes before the SUN rises).

    Hope this helps !

    Good hunting !

  • bwana

    Only time will tell… but I’ll be out looking for something fabulous!

  • gendotte

    I see that guest thinks it all came from Earth. I suppose that happened 6000 years ago, right? And the Grand Canyon? Why Noah’s Flood of course. I bet that Noah had a pet triceratops.

  • gendotte

    And Brian Thomas with his ‘Oort cloud doesn’t exist’. What about Xena and Gabrielle? (I think that the discoverer should keep the naming rights)

    • coreyspowell

      I’m always amused by people who ague that all of science, based on centuries of research by many thousands of careful observers, is all mistaken, but one factoid that fits their belief system must be the absolute truth…in this case, the out-of-context piece of information cited by Newsweek in 1998.

      Even the people who dispute science end up calling on the authority of science, which shows that even they recognize the power of scientific method.

  • williamstromberg

    where in the sky should we look N or S or E or W

    • JanetMermaid

      I know what you mean. I clicked on “A Novice Observer’s Guide” because I’m a novice. I was hoping for a MAP that shows where to look.


Out There

Notes from the far edge of space, astronomy, and physics.

About Corey S. Powell

Corey S. Powell is DISCOVER's Editor at Large and former Editor in Chief. Previously he has sat on the board of editors of Scientific American, taught science journalism at NYU, and been fired from NASA. Corey is the author of "20 Ways the World Could End," one of the first doomsday manuals, and "God in the Equation," an examination of the spiritual impulse in modern cosmology. He lives in Brooklyn, under nearly starless skies.


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