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Comet ISON Survives Perihelion (Barely) 62

Posted by Soulskill
from the still-alive dept.
An anonymous reader sends this update from NightSkyInfo: "Yesterday, when Comet ISON plunged through the solar atmosphere and behind SOHO's coronagraph (the black disk designed to block out the direct light from the Sun), its nucleus dwindled away to nothing and most of the tail simply evaporated. Everyone assumed that the comet completely disintegrated and died a fiery death. However, several hours after perihelion, ISON began to brighten up again. It is now distinctly evident on live images from SOHO, looks like a comet, and continues to brighten as it moves farther away from the Sun." Experts are unwilling to say precisely how intact the comet is — we'll need more data to make a conclusion about that — but astrophysicist Karl Battams says this is their best guess: 'As comet ISON plunged towards to the Sun, it began to fall apart, losing not giant fragments but at least a lot of reasonably sized chunks. There's evidence of very large dust in the form of that long thin tail we saw in the LASCO C2 images. Then, as ISON plunged through the corona, it continued to fall apart and vaporize, and lost its coma and tail completely just like Lovejoy did in 2011. (We have our theories as to why it didn't show up in the SDO images but that's not our story to tell - the SDO team will do that.) Then, what emerged from the Sun was a small but perhaps somewhat coherent nucleus, that has resumed emitting dust and gas for at least the time being. In essence, the tail is growing back, as Lovejoy's did.' Here's a GIF of the comet rounding the Sun (put together by Emily Lakdawalla).
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Comet ISON Survives Perihelion (Barely)

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  • by cunniff (264218) on Friday November 29, 2013 @11:21AM (#45555335) Homepage

    ...then what we have now are clearly leftovers.

  • XKCD (Score:5, Funny)

    by piripiri (1476949) on Friday November 29, 2013 @11:25AM (#45555369) Journal
    Oblig XKCD [xkcd.com]
  • by GameboyRMH (1153867) <gameboyrmh@@@gmail...com> on Friday November 29, 2013 @11:28AM (#45555389) Journal

    Sun: "Don't touch me, I'm hot!" 8-|

    ISON: "Gaaaah I can't stop or even slow down a little or change direction on my own!" D:

    Sun "Oh no you're trapped in my gravity now! This is gonna hurt!" 8-(

    ISON: "AAAAAAAAAH IT BURNS!!! AAAAH HELP! MAKE IT STOP!!!" D8

    Sun: "I can't, I wish I could! Oh man are you OK?" :O

    ISON: "Owww so much pain...." x_x

  • Time Travel (Score:5, Funny)

    by swinefc (91418) * on Friday November 29, 2013 @11:44AM (#45555491)

    Maybe it went back in time. You know, to save some whales.

    • Sounds like you've taken a little too much LDS.

      • by killkillkill (884238) on Friday November 29, 2013 @12:40PM (#45555893)
        I know they have some strange doctrines, but I don't think anything like that is part of their beliefs [wikipedia.org].
        • Is there any religion without strange doctrine?

          Other christians may find certain doctrines way out of the mainstream, but their is nothing in mormon doctrine or lore that's weirder than what one can find in the bible.

          • Every religion looks crazy to outsiders. Including the lack of religion.

            • So, every hair color looks crazy to outsiders. Including bald.

              Wait, what?

              Oh, right. It's that whole (lack_of_belief IS_NOT_EQUAL_TO any_superstition) thing again.

              • You've not debated enough believers then. A lot of them really do struggle to get their head's around the idea that someone could reject the idea of god. They can understand people believing in another god, or even in many gods - they disagree, but are at least on familiar ground. But no god at all? To them, the idea seems ridiculous out of hand. If there is no god, who could create the universe? What is the purpose of life? Was it all supposed to just pop into existance from nothing? It seems outragious to

          • by gl4ss (559668)

            I think it's fashionable to call them philosophies if there's nothing outright crazy on the menu.

            ALL HAIL THE MIGHTY COMET FOR IT IS MADE OF ELECTRICITY!

            (seriously, electric universe is the new funniest sect I know - "nope, can't be fusion.")

          • Is there any religion without strange doctrine?

            "One man's religion is another man's belly laugh." -- Robert Heinlein

      • by rwise2112 (648849)

        Sounds like you've taken a little too much LDS.

        It's LSD. Double dumbass on you!

        • by S.O.B. (136083)

          Sounds like you've taken a little too much LDS.

          It's LSD. Double dumbass on you!

          You and your colourful metaphors.

    • by JustOK (667959)

      That would be most logical.

  • TWO XKCD ! (Score:5, Funny)

    by mbone (558574) on Friday November 29, 2013 @11:51AM (#45555563)

    This one is directly relevant : http://xkcd.com/1297/ [xkcd.com]

    But this one is also relevant http://xkcd.com/1295/ [xkcd.com] given how many news sites mindlessly repeated the news "ISON disintegrated" when it was apparent in SOHO Lascar C3 imagery that that hadn't happened by 5 hours post-perihelion (see this at 2318 UTC [esa.int])

  • by Tolvor (579446) on Friday November 29, 2013 @11:58AM (#45555597)

    If ISON can survive its pass through the corona of the Sun, what else is possible?

    Will it be possible that Democrats and Republicans work together for the nation?
    Will RIAA/MIAA admit that they have been wrong and allow that piracy in fact is not as harmful to the music industry as they have said?
    Will sheeple wake up and take charge of their lives?
    Will Thanksgiving day shoppers will be calm, patient, and polite?
    Will my boss give me a raise?

    Yes I know people say "A snowball's chance in Hell", but a snowball just did... So will these now happen?

    • We had an opportunity for a "no chance in hell" to actually happen, and we wasted it on a frigging space iceball?

    • by ftobin (48814)

      Will it be possible that Democrats and Republicans work together for the nation?
      Will RIAA/MIAA admit that they have been wrong and allow that piracy in fact is not as harmful to the music industry as they have said?
      Will sheeple wake up and take charge of their lives?
      Will Thanksgiving day shoppers will be calm, patient, and polite?
      Will my boss give me a raise?

      In no particular order, "no", "no", "no", "no" and "probably not".

    • by Anonymous Coward

      Perhaps Ison has a rocky metal core with a magnetic field? Then by the laws of physics, any object in motion within a magnetic field develops an opposing magnetic field. That would be enough to deflect those charged particles accelerated by the local magnetic field of the Sun (1000 uTesla) and keep the nucleus cool as well as give it momentum.

      • by Anonymous Coward

        Perhaps Ison has a rocky metal core with a magnetic field? Then by the laws of physics, any object in motion within a magnetic field develops an opposing magnetic field. That would be enough to deflect those charged particles accelerated by the local magnetic field of the Sun (1000 uTesla) and keep the nucleus cool as well as give it momentum.

        Whoa. That certainly sounds like physics, but none of it is. No induced magnetic field is going to deflect supersonic charged particles. And they aren't carrying the bulk of the sun's heat, it's in the light. Maybe a better response would have been "Windmills don't work that way!"

  • by nherm (889807)

    I wonder if any of the several coronal mass ejections [wikipedia.org] that appear in the movie interacted with the plasma tail of the comet [iop.org].

  • That's no comet. It's a Klingon Bird-of-Prey!
    • by mrbester (200927)

      "We are going to attempt time travel... time travel... time travel" *bzzrt* *kshhh*

    • by koan (80826)

      Why would a ship with warp capability enter the solar system that way?

      • by fyngyrz (762201)

        Why would a ship with warp capability enter the solar system that way?

        Nav system was using meters. Navigator was using feet.

  • by mbone (558574) on Friday November 29, 2013 @12:47PM (#45555951)

    Did Comet ISON escape from the solar system ? Too soon to tell, but I would bet it has an even chance of being now unbound.

    According to the Minor Planet Center [minorplanetcenter.net], ISON has (had) a pre-perihelion eccentricity = 0.9999947.

    At perihelion, ISON was traveling at about 370 km / sec, and (given that eccentricity) was only about 0.7 m / sec below its escape velocity. Even a small nudge (of a few m / sec) "along track" thus could have enabled it to escape from the solar system forever (or bound it even more tightly), and (given the amount of mass it probably lost) it could have been thrusted by many 100's of m / sec. It's highly unlikely the outgassing thrust was purely at right angles to the direction of motion, so I would rate the probably of escape as ~ 50%.

    • I've got almost no intuition at these scales, but nudging a cometary nucleus by a few m/s seems like it would take a lot of energy -- maybe more than the processes acting on this comet are likely to generate.

      Now, nudging one chunk at the expense of the others is a different question. When a comet fragments, how quickly do the pieces typically separate? If the nucleus splits, forcing chunks apart at tens of m/s, the ones forced along track might get the boost they need -- but I don't know within an order of

      • by mbone (558574)

        I've got almost no intuition at these scales, but nudging a cometary nucleus by a few m/s seems like it would take a lot of energy -- maybe more than the processes acting on this comet are likely to generate.

        Now, nudging one chunk at the expense of the others is a different question. When a comet fragments, how quickly do the pieces typically separate? If the nucleus splits, forcing chunks apart at tens of m/s, the ones forced along track might get the boost they need -- but I don't know within an order of magnitude how fast the chunks are likely to be separating. Anybody?

        A lot of energy was available. It was about 3 radii from the Sun. It was hot enough to boil rocks.

        Suppose it lost 1/3 of its mass as water (steam) (so that the water lost had 1/2 the total mass). That steam could have left in a few jets, each with a velocity of 100 m / sec. If there were 100 jets, all distributed randomly about the surface, then the net velocity change would be ~ (1/2) * 100 m / sec / sqrt(100) or 5 m / sec, which is considerably more than 0.7 m / sec.

    • Outgassing doesn't apply as much thrust as you'd estimate - the comet spins, so most of the thrust is canceled out when it's facing the other way. If it's as marginal as you claim though...

      If it hasn't escaped, it looks unlikely to survive the next pass.

      • by mbone (558574)

        Yes, and it spins fairly rapidly (~2.4 hours period). However, we don't know what the spin angle is. Note that the cancelation you mention only applies for the equatorial component of thrusting, so the polar component could still change the semi-major axis, unless the spin axis is exactly perpindicular to the orbit plane. Note that, I was just trying to show, in a back of the envelope fashion, that there was likely enough thrust to be significant; I think that conclusion still stands.

    • So, why don't you measure the position of the incoming trajectory points and the outgoingetrajectory points, and then scale according to the known incoming orbit variables, and finally determine whether the outgoing orbit trajectory is parabolic or hyperbolic?

      • by mbone (558574)

        So, why don't you measure the position of the incoming trajectory points and the outgoingetrajectory points, and then scale according to the known incoming orbit variables, and finally determine whether the outgoing orbit trajectory is parabolic or hyperbolic?

        Oh, that will be done. But not today, and probably not for a few weeks (until it gets closer to the Earth). It's more fun to predict these things before the measurements are taken.

        • Some say the comet will end in fire; some say ice.

          I have a thought... I wonder if the comet #did disintegrate# in the Sun, but the shock wave re-coalesced the comet back into a plum-pudding lump of water, rock, and gas.

          In line with that, I also wonder has the comet's CN composition changed significantly?

    • The "tail" right now seems to be pointing towards the sun near perigee, and more in the direction of travel as time passes. Is that just debris, or a shock wave, or what? Or are those two ion jet engines, accelerating the vehicle out of here as quickly as possible "mission aborted!!! these folks are just too messed up.

  • ...bet there are some red faces back in the Oort cloud - especially among all the Shoemaker-Levy fanbois.

  • The linked gif "http://planetary.s3.amazonaws.com/assets/images/9-small-bodies/2013/20131128_ison_lasco-c2_20131129_0013_c2_1024.gif" seems to show the debris "tail" mostly flowing back along the comet's direction of travel, with some off-axis blow evident in the later post-encounter image. I would have expected the "tail" to always be pointing *away* from the sun as it made this fly-by. Derp?

    -DC

    • Re:A Tail's Tale (Score:4, Informative)

      by mbone (558574) on Friday November 29, 2013 @04:44PM (#45557477)

      The linked gif seems [amazonaws.com] to show the debris "tail" mostly flowing back along the comet's direction of travel, with some off-axis blow evident in the later post-encounter image. I would have expected the "tail" to always be pointing *away* from the sun as it made this fly-by. Derp?

      -DC

      There are generally two tails - the dust tail (which lies along the orbit path, like bread-crumbs in a fairy tale) and the (plasma) gas tail (which is blown by the solar wind, mostly directly away from the Sun). When you are just past perihelion ( as at the end of the linked-to video above) the dust tail can actually point (more or less) towards the Sun.

  • by notaspy (457709) <imnotaspy@@@yahoo...com> on Friday November 29, 2013 @02:48PM (#45556781)

    because it didn't have its ice on.

  • by koan (80826)

    The iron core survived and the out gassing gave it enough thrust to change orbit to a direct hit on Earth.

    Or not.

    ison, isoff

  • by dskoll (99328) on Friday November 29, 2013 @04:41PM (#45557463)

    {"composition":"iron","melting_temp_celcius":,"1538","will_disintegrate":"false"}

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