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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).
You realize that the sun doesn't actually have a surface, right? It's increasingly dense atmosphere all the way down.
Iron takes more energy to fuse than it releases. Any star with more than a trivial amount of iron tends to go kablooey, for that reason. Mainstream stars like the sun don't do that because they just don't have iron cores.
It's a small world and it smells funny; I'd buy another if it wasn't for the money; Take back what I paid (SoM)
nice Stargate Universe reference
---Saying gnome 3 is better than windows 8 not so much a compliment as it is damning with light praise.
Uh, the tail WAS blowing away from the sun. Take a look at the coronograph footage for a view that isn't wildly foreshortened:
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.
"FDA staff reviewers expressed concern about the number of patients who were left out of the study because they died."
This is true to a small extent, but there's a feedback loop where the star gets bigger and cooler if the fusion rate increases. This results in (predominantly) only one element being fused at a time, so you have Hydrogen->Helium (with some slightly heavier elements, C,N, and O can be involved) until the star is almost out of hydrogen, then Helium->Things between LIthium and Oxygen, and after that the star goes boom pretty quickly (or lacks the mass to go any further).
By comparison the amount of fusion of elements heavier than the one it is burning at the time is extremely small.
The majority of all stars (such as our own) are burning Hydrogen.
The majority of all heavy elements come from supernovae (the stars that our sun was made of before it became a star again).
That being said, there is probably a large chunk of iron and other heavy elements (from past supernovae) in the middle of our sun, but we generally ignore it because it is such a small percentage.
I was under the impression that stars, any star really, is continually increasing its stock of heavier elements. From Helium to Iron, and that these elements settle in the core in a layered fashion ordered by their atomic weights.
Then as it goes through its life cycles the star is progressively consuming heavier and heavier elements until there's little more than Iron left in the core and only then does it go kablooey.
"The onion of elements" happens at the end of star's life (or exiting of main sequence), but until then, there's plenty of hydrogen in core. Once star goes red giant, it has a helium core fusing to carbon (and hydrogen still fusing to helium in the mantle). If there's enough mass, the carbon core can start fusing neon, and so on all the way to iron. However, the full range with all the layers only happens in the most massive stars that finally explode as supernovas. And the main sequence is all about fusing hydrogen.
Indeed, that's a direct correlation to the hour the comet spent in the corona.
I was under the impression that stars, any star really, is continually increasing its stock of heavier elements. From Helium to Iron, and that these elements settle in the core in a layered fashion ordered by their atomic weights.
This happens once during the life of certain stars. Typically supergiants, and typically a second or two before a massive solarsystem devastating explosion.
The entire mess of nuclear reactions in a star make the core heavier and heavier UNTIL it fuses to iron. At that point there's no where left it go, it collapses, and violently ejects most of the outer layers. From what I've read over the billion year life of a star this all holds together for no more than a few seconds.
It may end the earth as we know it!
Man, everything ends the earth as we know it.
I could go out there and shit in the bushes and BAM, the earth as you knew it where that bush was shit free? GONE.
btw, don't go out to your bushes for another few minutes. Bring toilet paper.
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).
Touch everywhere, even when inappropriate.
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.
Seven puppies were harmed during the making of this post.
Neutrino measurements and extensive helioseismology.