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NASA Space Science

Comet Lovejoy Plunges Into the Sun and Survives 209

Posted by timothy
from the part-of-brian-aker's-career-path dept.
boldie writes with a link to NASA's account of comet Lovejoy's close encounter with the sun. Excerpting: "This morning, an armada of spacecraft witnessed something that many experts thought impossible. Comet Lovejoy flew through the hot atmosphere of the sun and emerged intact. ... The comet's close encounter was recorded by at least five spacecraft: NASA's Solar Dynamics Observatory and twin STEREO probes, Europe's Proba2 microsatellite, and the ESA/NASA Solar and Heliospheric Observatory. The most dramatic footage so far comes from SDO, which saw the comet go in (movie) and then come back out again (movie)." Here are larger QuickTime versions of the comet's entrance (22MB) and exit (26MB).
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Comet Lovejoy Plunges Into the Sun and Survives

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  • by Anonymous Coward on Sunday December 18, 2011 @02:11AM (#38414134)

    for a successful demonstration of Metaphasic Shields.

  • Misleading title (Score:5, Insightful)

    by aneroid (856995) <aneroid@gmaiDALIl.com minus painter> on Sunday December 18, 2011 @02:12AM (#38414138) Homepage Journal

    Sounds a lot more sensational when you compare the title's "comet plunges into sun and survives" event vs the actual "comet flew through hot atmosphere of the sun".

    /. worthy event nevertheless.

    • Re:Misleading title (Score:5, Informative)

      by MaskedSlacker (911878) on Sunday December 18, 2011 @02:15AM (#38414150)

      You realize that the sun doesn't actually have a surface, right? It's increasingly dense atmosphere all the way down.

      • by turing_m (1030530) on Sunday December 18, 2011 @05:40AM (#38414886)

        And here I thought it was turtles.

        • That was my first thought after I posted the comment too. I wish I could remember where I first heard that story. I want to say it was during a tour at the Palomar Mountain Observatory, but I'm probably mixing memories. It's only in the last five or six years that I've realized how many people know it, and how common a comment it is.

    • by tqk (413719)

      Sounds a lot more sensational when you compare the title's "comet plunges into sun and survives" event vs the actual "comet flew through hot atmosphere of the sun".

      Isn't the Sun's atmosphere supposed to be holy freakin' hell hotter than the Sun itself? Me, I'll just say "Way to go, Lovejoy!" (as in "Hunt for Red October").

      Cool stuff.

      • by symbolset (646467) *

        Cool stuff.

        Or maybe, not.

      • Re:Misleading title (Score:5, Interesting)

        by snowgirl (978879) on Sunday December 18, 2011 @03:20AM (#38414460) Journal

        Sounds a lot more sensational when you compare the title's "comet plunges into sun and survives" event vs the actual "comet flew through hot atmosphere of the sun".

        Isn't the Sun's atmosphere supposed to be holy freakin' hell hotter than the Sun itself? Me, I'll just say "Way to go, Lovejoy!" (as in "Hunt for Red October").

        Cool stuff.

        I think it might be something like the Leidenfrost effect. The sun's atmosphere vaporizes comet, and these vaporized comet parts shield the rest of the core from vaporizing. Only, this would have to work with the vapor blocking the radiation heat rather than the convection/conductive heat that the typical Leidenfrost uses. a.k.a. a sort of über-Leidenfrost effect.

      • Re:Misleading title (Score:5, Informative)

        by reverseengineer (580922) on Sunday December 18, 2011 @03:28AM (#38414484)
        The sun's corona is intensely hot- about 1 million kelvin, much hotter than the photosphere beneath, but the plasma is very diffuse. The photosphere, the layer that appears to us to generate the opaque disk of the sun (and is the closest thing it has to a surface) is a mere 6000K, but it's 10^12 times denser than the corona. In turn, the photosphere is about one ten-thousandth of the density of Earth's atmosphere at sea level. This really skews notions of "temperature" when we talk about a star. On Earth, we're used to objects placed in a medium fairly rapidly equilibrating to the temperature of that medium. We realize that some substances conduct faster or slower than others, but overall putting something in a hot environment makes it hot.

        For all but the most finicky of physics experiments, if we had pressure conditions of the density of the sun's corona, it would be "high vacuum." Very little conduction of heat from the plasma to a comet is going to take place. The bombardment by solar photons and the gigantic magnetic and gravitational fields of the sun play a greater role here than the actual material of the sun, and thus NASA can be pleasantly surprised by Comet Lovejoy's survival of its close encounter. But it's the wrong idea to picture this comet plunging into some sort of molten inferno. Of course, the sun's core is another story. 15 times denser than lead and 16 million kelvin. I'll like to see the comet that survives that.

        • Re:Misleading title (Score:5, Informative)

          by PyroMosh (287149) on Sunday December 18, 2011 @05:29AM (#38414848) Homepage

          The effect we're discussing is easily observable to anyone who's reasonably familiar with a kitchen.

          Ever fry french fries in oil? This is typically what? 350F?

          Baking a pizza will typically be around 450F.

          Yet it's easy to reach into a 450 degree oven and remove the pizza. As long as you use a towel or a tool, your hand can be in the same environment that just cooked the pizza for a relatively long time..

          But any fool knows that reaching into the oil with your bare hand *at all* will burn your skin in less than a second. Even though the oil is 100 degrees cooler than the oven.

          It's just a dramatic, every-day example of the difference in heat transfer between mediums (in this case, oil vs air).

          • by jrumney (197329)
            I thought the GPs post was more about deep fried ice cream than putting hands in the oven.
            • by jrumney (197329)
              Then again, I might be looking at the wrong GP, a post about the Leidenfrost effect appeared above the GP when I was reading this.
      • Sounds a lot more sensational when you compare the title's "comet plunges into sun and survives" event vs the actual "comet flew through hot atmosphere of the sun".

        Isn't the Sun's atmosphere supposed to be holy freakin' hell hotter than the Sun itself? Me, I'll just say "Way to go, Lovejoy!" (as in "Hunt for Red October").

        Cool stuff.

        It is true that the Sun's corona is extremely hot, but it also has an extremely low density. Together that means that the corona may not impart much of an energy flux to the surface of the comet. Without knowing the numbers, my guess would be that radiation from the sun is a more important contributor to melting of the comet.

        Consider another situation: the temperature of the plasma in the earth's magnetosphere can be thousands of degrees, and yet spacecraft don't melt in it, for the same reason.

  • Composition? (Score:4, Interesting)

    by martas (1439879) on Sunday December 18, 2011 @02:18AM (#38414160)
    What the hell is that thing made of? Article doesn't seem to say, and I'm sure nobody is 100% certain, but any guesses as to its composition based on its orbit? Also what would the temperature of such an object likely be?
    • by galaad2 (847861)

      Orbit? that thing no longer has a stable orbit... at least for a while it won't have, until it stabilizes.

      have you seen those two movies? its exit is like an out-of-control fire hose with afterburners.

  • by JO_DIE_THE_STAR_F*** (1163877) <`jody29' `at' `gmail.com'> on Sunday December 18, 2011 @02:19AM (#38414164)
    That wasn't a comet it was Kirk and company in a Klingon Bird-of-Prey trying to get back to the 23rd century.
  • by circletimessquare (444983) <circletimessquare AT gmail DOT com> on Sunday December 18, 2011 @02:19AM (#38414168) Homepage Journal

    "The Sun somehow survives close call with badass comet Lovejoy. Meekly vows to be more respectful next time."

  • by Anonymous Coward on Sunday December 18, 2011 @02:23AM (#38414194)

    The comet's fuel reserves were low; flew into a star to recharge.

  • by Anonymous Coward on Sunday December 18, 2011 @02:24AM (#38414202)

    Just as you can plunge your hand in a dewar of liquid nitrogen and not have your hand immediately frozen, a comet will survive for the same reason. With your hand, the liquid nitrogen boils from the heat of your hand creating an insulating layer of air between your hand and the liquid nitrogen. With the comet, the comet evaporates creating an insulating layer of gasses that protect the entire from immediately evaporating.

    I've kept my fist in liquid nitrogen for a total of 38 seconds. (Not the smartest thing I've done.) I had a touch of frost bite on the pads of my fingers where liquid nitrogen seeped into my fist and the gasses escape properly and couldn't insulate as needed. The rest of my hand was just fine and I could have probably left it in there longer had I chose with little ill effects -- other than on the pads of my fingers.

    • Re: (Score:2, Funny)

      by Anonymous Coward

      I've kept my fist in liquid nitrogen for a total of 38 seconds. (Not the smartest thing I've done.)

      May not be the smartest thing you have done. But I suppose it is the coolest thing you have done.

    • you forgot the "don't try this at home, kids"

      no, seriously

  • by jd (1658) <imipak&yahoo,com> on Sunday December 18, 2011 @02:26AM (#38414214) Homepage Journal

    Basic chemistry tells us that heat transfer isn't instantaneous, that solid objects remain at melting point until fully melted, and that heat != temperature. It's why you can walk over hot coals without burning yourself. The composition of the comet would be easy to determine, since absorption spectrometry will tell you what the tail is made of. We also know, from the Giotto probe, that comets don't evaporate from the outside. That was one of the biggest blunders in the mission. Never, ever make assumptions in science because it WILL bite you. Facts are the only acceptable currency.

    • Re: (Score:2, Funny)

      by Anonymous Coward

      That's the weirdest combination of terrible and excellent science education ever. Congrats.

    • by CODiNE (27417)

      It's why you can walk over hot coals without burning yourself.

      Actually it's the Leidenfrost effect [wikipedia.org]. Try that with dry feet and let me know how long it is before you can walk again.

      • by pjt33 (739471)

        Wet skin conducts heat better than dry skin, so it's often recommended to firewalk with dry feet rather than wet feet.

  • No Audio (Score:5, Funny)

    by Cylix (55374) * on Sunday December 18, 2011 @02:32AM (#38414262) Homepage Journal

    I'm pretty sure it was shouting, "Hot hot hot hot!"

    I'm fairly certain comet love joy won't be taking on any more dares for a while.

  • Velocity of Comet (Score:5, Interesting)

    by dispersionrelation (2534290) on Sunday December 18, 2011 @02:34AM (#38414274)
    I went ahead and calculated the velocity of the comet at its Perihelion (closest distance to the sun) to be or 618km/s which is the same as 383 mi/s which is the same as 0.2% the speed of light, very fast!
    • Re:Velocity of Comet (Score:4, Interesting)

      by MichaelSmith (789609) on Sunday December 18, 2011 @03:23AM (#38414472) Homepage Journal

      Sound like the ideal place to start your interstellar ramjet engine.

    • Re:Velocity of Comet (Score:4, Informative)

      by Dunbal (464142) * on Sunday December 18, 2011 @05:55AM (#38414930)
      I think that's slightly above the solar escape velocity, so we can kiss this one goodbye. Don't worry boys, he won't be coming back.
      • But wasn't it in some sort of orbit around the sun before? Where did it pick up the extra energy to get away from the sun, then? If anything, I would have expected its orbit to shrink.
        • Re: (Score:3, Interesting)

          by f()rK()_Bomb (612162)
          The gases boiling off the comet effectively give it a rocket engine. One of the proposed methods to deflect a comet on a collision with earth is to shine sun on it with giant mirrors.
          • But that "rocket engine" would work in opposite ways on arrival and departure, either slowing it down or speeding it up (not sure) when it's coming in and doing the exact opposite when it's emerging again. So that would not give it a net extra energy. Or am I missing something?
            • by pjt33 (739471)

              I haven't worked through this in any detail, but it seems plausible that there could be a net push away from the Sun on the basis that the incoming comet is larger and hence has a lower surface area to mass ratio.

            • by Solandri (704621)
              The comet shrinks as it gets sublimated away by the heat. This leads to both a decrease in mass and surface area. Modeling it as a sphere:

              m ~ V (mass is proportional to volume)
              V = 4/3 pi * r^3
              so r ~ m^(1/3)
              surface area = 4 pi * r^2
              so SA ~ m^(2/3)

              Assuming the velocity of a vaporization jet is constant (constant sublimation temperature means gas molecules have constant kinetic energy), the force is proportional to the amount of escaping gases. The amount of escaping gases is proportional to surfa
        • by Dunbal (464142) *

          From a near miss. The sun's gravity accelerates it as it falls close in to the sun - gravity is dependent on the inverse of the distance squared. So as it gets very close the gravitational pull grows along square function. By not actually hitting the sun, it manages to keep some of that energy (and the sun loses the same amount in angular momentum - but for the sun it's a negligible amount of spin so you won't notice). Because its velocity is far, far greater than the (I believe it's 33km/s) escape velocity

          • No, that's definitely not how it works. For a small object passing close to a massive object, if no other forces like friction or electric forces exist, and disregarging relativistic effects, the exit velocity will be exactly equal to the approach velocity. The sum of potential and kinetic energy remains the same: as it loses potential energy in the gravitational field by coming closer, it will speed up and it will lose this speed again when going back up in the gravitational field. The decelleration while

    • Which explains why it didn't evaporate. Time contraction!
  • by Squiddie (1942230) on Sunday December 18, 2011 @02:36AM (#38414294)
    It would be cool if that were the case, then we would just have to make some ships or probes from that. Indestructible space-craft. Might be nice.
  • Is this a Simpson's prank?
  • Oh my (Score:4, Funny)

    by lxs (131946) on Sunday December 18, 2011 @03:05AM (#38414416)

    "What," said Trillian in a small quiet voice, "does sundive mean?"

    "It means," said Marvin, "that the ship is going to dive into the sun. Sun... Dive. It's very simple to understand. What do you expect if you steal Hotblack Desiato's stunt ship?"

    "How do you know..." said Zaphod in a voice that would make a Vegan snow lizard feel chilly, "that this is Hotblack Desiato's stuntship?"

    "Simple," said Marvin, "I parked it for him."

    "The why... didn't... you... tell us!"

    "You said you wanted excitement and adventure and really wild things."

    If DNA was still alive he'd have to do a lot of rewriting.

  • What an awesome solar system we've got!
  • When the Dead Kennedy's Jello-of-"California Uber Alles"-and-"Holiday in Cambodia"-fame
    (amongst other faves) was running for mayor of San Francisco,
    one of his heartfelt pleas was that he'd be the first politician to spearhead the idea of
    "landing a man on the sun".

  • by Chelloveck (14643) on Sunday December 18, 2011 @11:47AM (#38416678) Homepage
    So, a snowball really does have a chance in hell.
  • There is something wrong with the exit movie. Normally, the comet tail runs aways from the Sun but in this video it appers to run in the opposite direction.
  • Like in Arthur C. Clarke's story "Sunrise" (I think), a spaceship gets very close to the sun by remaining in the shadow of a sun grazing asteroid.

    Probably wouldn't be a good idea to use a comet because of all the outgassing (in addition to being dangerous and literally blowing you away, it would mess up the measurements). Also, a quickly rotating asteroid wouldn't be good as the surface would be re-radiating the heat directly below you. If we could find a sufficiently large asteroid (for it's heat capacit

  • by Maxmin (921568) on Sunday December 18, 2011 @05:41PM (#38419164)

    ...must be laughing right now over another narrow escape.

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