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).

Comments

You can all thank Dr. Reyga...

[Anonymous Coward]

for a successful demonstration of Metaphasic Shields.

Misleading title

[aneroid]

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

[MaskedSlacker]

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

Re:Misleading title

[jd]

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.

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:Misleading title

[reverseengineer]

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

[schroedingers_hat]

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.

Re:Misleading title

[Zarhan]

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.

Re:Misleading title

[thegarbz]

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.

Re:Misleading title

[PyroMosh]

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).

Re:Misleading title

[turing_m]

And here I thought it was turtles.

Re:Misleading title

[Anonymous Coward]

That's quite a bold statement!

Re:Misleading title

[MaskedSlacker]

No you couldn't.

At a certain point you'd reach neutral bouyancy and stop sinking (ignoring the part about you vaporizing from the temperature). This is still not the same as there being a surface (and in point of fact is COMPLETELY unrelated to what is usually referred to by the term "surface of the sun"). There is no meaningful line of demarcation between "below the surface" and "above the surface," and the term surface NECESSARILY implies a demarcation. The use of the term "surface" in the case of stars (and gas giants) is purely terrestrial metaphor, and it's fine as far as that goes--but only that far. Take the metaphor further (as my parent did in taking it literally), and you wind up reaching physically absurd conclusions (as you also have).

As for tomatoes, all I care about is that they're fucking delicious.

You'd be better off trying to claim that black holes have a surface. They don't, but at least they do have a clear demarcation between above and below their "surface." Stars do not.

FWIW, real astrophysicists define the surface of the sun as the radius which equals an optical depth of 2/3. This is a useful demarcation (though not a terribly clear one, since the optical depth is wavelength dependent) for observational purposes, but not for kinematic ones (such as when talking about comets flying into, and out of, the sun).

Re:Misleading title

[JTW]

A thought experiment worthy.

If you took a ball of Iron the size of say planet Earth, and it were to plunge into the heart of the Sun. What would be the result.. a Nova, SuperNova.. fizzle.

And what if it were slightly off target and merely circled the center for a while.. would it retain its shape or spinout into a smeared ball of plasma.. undoing the star?
Something somewhat like this probably already happened.. the Lithium content of our star for example.. guess it just wasn't significant emough.

Klingon Bird-of-Prey

[JO_DIE_THE_STAR_F***]

That wasn't a comet it was Kirk and company in a Klingon Bird-of-Prey trying to get back to the 23rd century.

Re:Klingon Bird-of-Prey

[The Grim Reefer]

That wasn't a comet it was Kirk and company in a Klingon Bird-of-Prey trying to get back to the 23rd century.

Those thieving bastards just took off with a pair of my whales too. -Ismael

Better title:

[circletimessquare]

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

Energy Depleted

[Anonymous Coward]

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

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.

I'm surprised they're surprised.

[jd]

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:we are all doomed!

[Colonel Korn]

It's going to come back and smash into the earth in 2012.

Quite possible as, quoting TFA:

"There is still a possibility that Comet Lovejoy will start to fragment,"

No telling which directions those pieces might fly off.

Absolutely. When a single object slowly fragments due to thermal gradients, it ignores conservation of momentum and sometimes even conservation of mass. It's possible this ~100-500 m radius comet will launch a 50000 m chunk at us with a velocity of over half the speed of light!

No Audio

[Cylix]

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.

Re:No Audio

[Krishnoid]

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

Shortly after which it reported, 'I got a little cooked but I'm ok'.

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:That's not a comet.

[Anonymous Coward]

Uh, the tail WAS blowing away from the sun. Take a look at the coronograph footage for a view that isn't wildly foreshortened:

Re:Awesome

[durrr]

It's actually an aerobraking alien spacebattleship. We're so fucked.

Re:Awesome

[Jeremiah Cornelius]

Hey that line about "comet Lovejoy plunging into the sun.."

I just used it on some bird in the pub, and it worked!

Re:we are all doomed!

[Anonymous Coward]

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.