Comet Lovejoy Plunges Into the Sun and Survives

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).

Composition?

[martas]

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?

Of course it is possible ....

[Anonymous Coward]

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.

Velocity of Comet

[dispersionrelation]

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:Misleading title

[Anonymous Coward]

http://www.thesurfaceofthesun.com/
Maybe that depends on your definition of a surface?

Re:Misleading title

[snowgirl]

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:Velocity of Comet

[MichaelSmith]

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

Re:Velocity of Comet

[f()rK()_Bomb]

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.