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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).
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.
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!