Changing Planet

Comet ISON Plays Coy With Astronomers


Hubble Space Telescope got its first look at comet ISON back in April and found that it exhibited some curious properties. Credit: NASA/Hubble Space Telescope
Hubble Space Telescope got its first look at comet ISON back in April, and the newly released findings show that that the icy interloper exhibited some curious properties. Credit: NASA/Hubble Space Telescope

The latest observations from professional and amateur astronomers around the world show that the much-hyped comet ISON is still very much alive, and new data suggests that it may very well survive its close swing by the Sun on November 28.

The big question on skywatchers’ minds, however, is how good of a sky show ISON will put on in the coming weeks and months. (See also Comet ISON: Pop or Fizzle?)


New studies presented at the American Astronomical Society’s Division for Planetary Sciences meeting this week in Denver suggest that ISON is not a puny comet. Its nucleus measures somewhere between 1 to 4 km across—which bodes well—meaning that it shouldn’t disintegrate from the intense heat during its sun-grazing pass.


This image shows comet ISON as it appeared to pass by the planet Mars on October 5, 2013. Credit: Michael Jäger, Weißenkirchen, Austria

Hubble observations from back in April  hint that the axis of spin (or pole) of the comet’s nucleus is continually pointing towards the Sun. If this is the case, then one hemisphere of the comet is always facing away from the sun.

This could be both bad and good news for comet watchers.  As the comet continues to plunge towards the sun, intense solar radiation and tidal forces will hit its sun-facing side,  possibly pulling the comet apart. But because one side of the comet has been in the dark, it has remained frozen and in pristine condition.

As of early October comet ISON  has formed a distinct tail and shines with a green glow, but is still a telescopic object shining at magnitude 11.

According to Hubble data, ISON  should continue to possess the same axis of rotation until it rounds the sun at the end of November, at which time the other, untouched hemisphere will suddenly get blasted with scorching heat as it starts its journey back to the outer solar system.  The sun’s fire may possibly cause an outburst of gas and dust as the comet’s hitherto unexposed surface-ice sublimates at high rates.

“We measured the rotational pole of the nucleus.  The pole indicates that only one side of the comet is being heated by the Sun on its way in until approximately one week before it reaches it closest point to the Sun,” said Planetary Science Institute scientist Jian-Yang Li, who led the team that imaged the comet with Hubble in news statement.
“Since the surface on the dark side of the comet should still retain a large fraction of very volatile materials, the sudden exposure to the strong sunlight when it gets closer to the Sun than Mercury could trigger huge outbursts of material,” Li said.

If these predictions hold true, then the best sky show for ISON may come in December and into the new year. However because these observations date back to April, the comet may have changed its rotation since then. Hubble is scheduled to do follow-up observations this month and the new data will surely help narrow down comet ISON’s potential performance.

For now it’s anyone’s guess what ISON will do—so we’ll just have to wait and see.


Follow Andrew Fazekas, the Night Sky Guy, on Twitter and Facebook.

Andrew Fazekas, aka The Night Sky Guy, is a science writer, broadcaster, and lecturer who loves to share his passion for the wonders of the universe through all media. He is a regular contributor to National Geographic News and is the national cosmic correspondent for Canada’s Weather Network TV channel, space columnist for CBC Radio network, and a consultant for the Canadian Space Agency. As a member of the Royal Astronomical Society of Canada, Andrew has been observing the heavens from Montreal for over a quarter century and has never met a clear night sky he didn’t like.
  • randy bauer

    I find this coyness annoying. Let’s have a comet party!

  • syney

    I LOVE COMET ISON ! Cant what till Nov,28,2013.

  • miguel

    Comet Ison is a huge space ship from the Andromeda Galaxy. That is why the surprising , unexpected behavior from it. Watch out for more.
    Check out:

  • What you mean

    “the comet may have changed its rotation since then.”

    really….and hows that.

    • to clarify..a different side of the comet may now be facing the sun since the Hubble measurements were made back in April.

  • Nova Celeste

    Interactions with the sun’s magnetic field from ISON causing earthquakes. ISON lite up MARS during passby. ISON Will shut down power grids if that happens in Dec. Earth flyby and meteors are already coming down like crazy from ISON’s debris trail. And NASA shuts down during this historic event? SMOKESCREEN! What’s in their Closet?

  • jeff saylor

    as an amateur/novice I wish the experts would continue to speak in a language I/we non-pro sky watchers can better understand. Most watchers have no idea what, for example, parallax means and henceforth lose interest as it all sounds so complicated when in realty it needn’t be.

  • Don Moler

    At the earths surface, on a very clear day,when the sun is directly overhead, the sun’s output is aprox 1000 watts per square meter. I would like someone to calculate how many watts per square meter will there be on Ison at its closest to the sun??? This would be interesting to know…. Don

  • keith Long

    Andrew, how could it be a different side if the axis is continually pointed at the sun Can’t have both.

  • Mike Hager

    The axis of rotation can have a wobble, like a top. The Earth’s axis wobbles but over periods of many thousands of years. Smaller bodies, though, can have very rapid wobble, by comparison. There must not have been enough resolution in images over a period of time to characterize this for ISON at time of article. Also, the dynamic out-gassing forces may affect the wobble…not sure on this point.


    Any chance comet / fragments hit n.america?

  • Northern Norm

    Sure it is, Miguel. Hope they have some really good A/C on board for their close encounter with the sun….or are they going to change their course? hahaha
    What you mean, if the axis is pointing at the sun on its way in, it will be pointing away from the sun on its way past, and continue to point towards the sun on its way back out. That is, if the N pole is pointing at the sun on its way in, then its S pole will be pointing at the sun on its way out…hence the S hemisphere will be exposed to the sun on its way out instead of the N hemisphere. Unless gravitational forces changes it during its round-about of the sun.

  • james

    We’re all going to die

  • Mark

    Nice article Andrew. But if one hemisphere of the comet is permanently facing the sun this is presumably because of the center of gravity of the comet. Unless sublimation causes a change in the center of gravity the same hemisphere will continually face the sun regardless of proximity.
    Also, because of its projected orbit, it would be interesting to speculate on the possible ramifications to earth of a potential disintegration of Ison. Now THAT would invoke interest in this comet !

  • Shawn Harrington

    Maybe it will break in two pieces. One piece for the White House and one Piece for the Capital Building!

  • Paul H.

    Oh Boy, we’re all going to get “Isonized”

  • Kjirstin

    How is it that the front surface in many images appears warped rather than round? When I put it into a Lightroom program and drop the exposure (make it darker) I can see three very sharp and distinct images. If a comet were in pieces, wouldn’t they be irregular? These are crisp; a center ball, balanced by two rods exhibiting equidistant definition. What’s up with that stuff? It looks more like formation flying.

  • john

    What about all the asteroids the comet has displaced on its journey through the asteroid belt coming oure way soon …?

  • William Miller

    I have read that Ison will come closer to Earth after its pass by the sun. So close that it will be lower than the orbit of our satellites. Surely this can cause some problems. Maybe it might knock down a few of those pesky things. Seriously it could cause major consequences. Remember you can use a microwave as a Faraday cage for your communication devices.

  • marty

    no my last name is not mcfly. i do not know the future, however all this distraction with the us government shutdown and such is very coincidental at the least. i think nasa knows more than we think about this comet. something strange is going on here…

  • Shawn

    I truly hope this comet stays intact. If that happens I’ve been told we would be able to see the coma during the day when it’s at it’s closest approach on Dec 26th. That would be a very cool thing to see. Keep it together ISON.

  • yuri krell

    ,,moderate,, as you see fit.
    the truth is undeniable.

  • Lynn


    October 16, 8:16 pm
    How is it that the front surface in many images appears warped rather than round? When I put it into a Lightroom program and drop the exposure (make it darker) I can see three very sharp and distinct images. If a comet were in pieces, wouldn’t they be irregular? These are crisp; a center ball, balanced by two rods exhibiting equidistant definition. What’s up with that stuff? It looks more like formation flying.

    My response to Kjrstin: yes it looks like a formation because Ison is a biosphere & accompanied by 2 city size spaceships. They are our ancestors. This what that native indians are waiting for, the blue star kachina, If war occurs here because the elites had planned this war agenda long ago, there will be no nuclear weapons that will kill us. They will interfere. Research the truth. the truth of humanity.

  • Dave

    What is with all the paranoia? Lower than satellites? No it’s isn’t even going to come within the distance of Earth to Venus. In fact we are on the OTHER side of the sun during its close approach, it will be going AWAY from Earth as we observe it in late December. Three images? that’s because its three photos, it’s called exposure, Hubble took three photos from three different positions, they have been lined up to make one clear image. The rest of the world is excited to see Ison, while America is engaged in it’s ever growing uneducated paranoid conspiracy theories about space. Earthquakes? Where is the science in any of these theories, where is the logic, Ison is a mosquito.

  • anno

    This comet will pass directly over earths nth pole meaning it intersects earth perfectly now what if the government has lied about its trajectory around the sun and it heads back towards earth on the solar plane!? IT WILL BE A DIRECT IMPACT.but even if nasa’s data is correct and it passes over our planets nth pole isons approach will put earth INSIDE the comets tail and coma causing massive meteor storms and also any toxins(poisonous gasses or microbial organisms) in the tail debris will make it to earths surface making everyone sick or worse.

  • Bob Laliberte

    Is it just a coincidence that FEMA is planning this huge drill in November ?

  • Forrest Carr

    Interested in comet doomsday theories? Already the Internet is abuzz with this one (Google “comet ISON black death” and see for yourself). Want more? Comet ISON plays a role in my new just-published science fiction novel, “A Journal of the Crazy Year.”

    — FC

  • Juls

    I would like to know the best times (day*night) to view the Ison comet from North Hemisphere, Southern Hemisphere, Africa, ect. during Nov. and any new pictures since it passed Mars

  • grant

    First contact anyone?

  • Frank Peters

    Wow, reading these comments. I can’t help wondering, how many of you people finished high school?

  • Thomas Essers

    I would like to know something about Comet ISON.
    When will I be able to see the comet in his best condition? and at what time? You guys would do me a big favor if you could say me when. please respond, i beg u !

  • Sarah Arnold

    Andrew,tell these people to chill!!we are not going to die…….we are still going to live until God comes back,oh,I think I just told them.

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