Comet Lovejoy Plunges Into the Sun and Survives 209
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 can all thank Dr. Reyga... (Score:5, Funny)
for a successful demonstration of Metaphasic Shields.
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Actually, that comet was Gomtuu trying to kill itself again.
Misleading title (Score:5, Insightful)
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".
Re:Misleading title (Score:5, Informative)
You realize that the sun doesn't actually have a surface, right? It's increasingly dense atmosphere all the way down.
Re:Misleading title (Score:4, Funny)
And here I thought it was turtles.
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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.
Re:Misleading title (Score:5, Informative)
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 (Score:5, Insightful)
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.
Re:Misleading title (Score:5, Informative)
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.
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Re:Misleading title (Score:5, Funny)
That's quite a bold statement!
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Quick question to someone who seems like he might know: is the current stock of hydrogen in the universe all that will ever exist, or does the stock get replenished (so to speak) during a supernova as heavier elements get split into lighter ones? Just wondering if there could ever be a point in the lifetime of the universe when light elements like hydrogen and helium simply don't exist any more.
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Re:Misleading title (Score:5, Informative)
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 (Score:5, Informative)
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.
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That iron core is still a gas. We're just not used to iron being a gas because we live at such cold temperatures.
Re:Misleading title (Score:5, Insightful)
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).
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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.
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Cool stuff.
Or maybe, not.
Re:Misleading title (Score:5, Interesting)
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)
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)
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).
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Neutrino measurements and extensive helioseismology.
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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)
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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.
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Klingon Bird-of-Prey (Score:4, Funny)
Re:Klingon Bird-of-Prey (Score:4, Funny)
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
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People who did a little too much LDS in the '60s.
Re:Klingon Bird-of-Prey (Score:4, Funny)
People who did a little too much LDS in the '60s.
What did the Mormons have to do with Start Trek?
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Nothing -- that was Battlestar Galactica.
Better title: (Score:5, Funny)
"The Sun somehow survives close call with badass comet Lovejoy. Meekly vows to be more respectful next time."
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Pah, Chuck Norris is a wimp.
http://www.wnd.com/?pageId=101063 [wnd.com]
Afraid of Obama!
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Show a little respect. Reverend lovejoy is a badass preacher who can take on a tribe of baboons bare handed. Being gay wouldn't be compatible with his christian values, and you can tell he's not gay because he has kids with his beard, I mean, his wife.
Energy Depleted (Score:5, Funny)
The comet's fuel reserves were low; flew into a star to recharge.
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nice Stargate Universe reference
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Of course it is possible .... (Score:5, Interesting)
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.
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May not be the smartest thing you have done. But I suppose it is the coolest thing you have done.
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you forgot the "don't try this at home, kids"
no, seriously
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Though, to be fair, the comet had slightly more mass than his balled fist.
I'm surprised they're surprised. (Score:5, Insightful)
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.
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That's the weirdest combination of terrible and excellent science education ever. Congrats.
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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.
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Wet skin conducts heat better than dry skin, so it's often recommended to firewalk with dry feet rather than wet feet.
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Yes and ice cubes are even easier to walk over. Perhaps wearing shoes can prevent getting paint on ones feet, thereby eliminating the Leidenfrost effect entirely.
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See CODiNE's response for why humans do indeed ablate material.
No Audio (Score:5, Funny)
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 (Score:5, Funny)
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'.
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Oh, no, not again.
Velocity of Comet (Score:5, Interesting)
Re:Velocity of Comet (Score:4, Interesting)
Sound like the ideal place to start your interstellar ramjet engine.
Re:Velocity of Comet (Score:4, Informative)
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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.
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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
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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
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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
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Maybe it's made of a great material (Score:3)
Whaaat? (Score:2)
Oh my (Score:4, Funny)
"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.
Re:Oh my (Score:4, Funny)
Fortunately any occupants of that comet have long since used the partly working teleport to get the hell out of our solar system.
Wow! (Score:2)
Reminiscence of a Jello Biafra-for-mayor slogan (Score:2)
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".
And now we know... (Score:4, Funny)
Something is wrong (Score:2)
Someday I hope we can follow (Score:2)
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
Lovejoy and Tinker... (Score:3)
...must be laughing right now over another narrow escape.
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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.
Re:we are all doomed! (Score:5, Funny)
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!
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and I feel fine.
Re:we are all doomed! (Score:5, Informative)
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.
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Great, you just gave SyFy it's next disaster movie. And yet I'm still a sucker for them, heh.
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Meter is a unit of length, not mass, so you're obviously wrong! I'm already living in my bomb shelter
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Stop hassling Hollywood with your "physics"! :P
Re:we are all doomed! (Score:4, Funny)
Oh great. A big ball of ice passes through fire, survives, catches on fire, and now it's coming for us. Ice on fire. How do we even stop that?
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Comet Lovejoy flew through the hot atmosphere of the sun and emerged intact. ..
Should it have not went back in time? I seem to remember that being a rule...
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Comet Lovejoy flew through the hot atmosphere of the sun and emerged intact. ..
Should it have not went back in time? I seem to remember that being a rule...
Only if it was using Star Fleet technologies. Apparently, there is some interference between the warp or impulse engines and the solar core that causes it - perhaps there is a quantum black hole in the center or something, or else everyone would have done it at their own star and the Klingons, Romulans, or Borg would have conquered the galaxy by thousands or million of years before their founding.
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...maybe it was the Destiny.
Re:That's not a comet. (Score:5, Informative)
Uh, the tail WAS blowing away from the sun. Take a look at the coronograph footage [nasa.gov] for a view that isn't wildly foreshortened:
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Uh, the tail WAS blowing away from the sun. Take a look at the coronograph footage [nasa.gov] for a view that isn't wildly foreshortened:
Exactly. Therefore the matter in the vids was the comet losing mass.
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TFA has some speculation regarding that phenomena. Solar wind, magnetics, gravity, who knows at this point? Are you suggesting that it was really a rocket?
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I keyed on that "armada" myself. Had to read TFS, so see where this "armada" came from. Unfortunately, the word has no bearing on the story - it was just thrown in there, much as the word "decimate" is oftentimes improperly used to generate attention.
One would expect an "armada" to, at the least, come under one common authority, and to share a common mission.
Re:Awesome (Score:5, Funny)
Re:Awesome (Score:5, Funny)
Hey that line about "comet Lovejoy plunging into the sun.."
I just used it on some bird in the pub, and it worked!
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It's actually an aerobraking alien spacebattleship. We're so fucked.
Or it's refueling....