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Space Earth Science

Astronomers Say Dying Sun Will Engulf Earth 343

iamlucky13 writes "A minor academic debate among astronomers is the final fate of the earth. As the sun ages and enters the red giant stage of its life, it will heat up, making the earth inhospitable. It will also expand, driven by helium fusion so that its outer layers reach past the earth's current orbit. Previously it had been believed that the sun would lose enough mass to allow earth to escape to a more distant orbit, lifeless but intact. However, new calculations, which take into account tidal forces and drag from mass shed by the sun, suggest that the earth will have sufficiently slowed in that time to be dragged down to its utter destruction in 7.6 billion years. "
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Astronomers Say Dying Sun Will Engulf Earth

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  • by ChrisGilliard ( 913445 ) <christopher DOT ... AT gmail DOT com> on Wednesday February 27, 2008 @01:05AM (#22569414) Homepage about global warming!
  • Ah well... (Score:2, Informative)

    by QJimbo ( 779370 )
    All good things...
  • Maybe (Score:2, Funny)

    by QuantumG ( 50515 )
    But maybe replicating space organisms that live in the Oort cloud will come and put a protective membrane around the Earth before then slowing down the passage of time on Earth in relation to the rest of the galaxy so we can be united with other sentient beings in worlds connected to our own by giant arches poking out of the sea.

    Ahh, Robert Charles Wilson, you Spin me right round.

    • By this time if humans have not established self sufficient colonies around many different stars they deserve to die out.

      This is a test. This is the only test.

  • Last post (Score:5, Funny)

    by Harmonious Botch ( 921977 ) * on Wednesday February 27, 2008 @01:07AM (#22569436) Homepage Journal
    Heck, 7.6 billion years is ok by me; Chun the unavoidable will have been at my elbow by then.
  • This is news? (Score:5, Informative)

    by Cobalt Jacket ( 611660 ) on Wednesday February 27, 2008 @01:07AM (#22569438)
    This is the way I was taught it would happen on astronomy shows from the 1980s. I don't get the big deal.
    • Re:This is news? (Score:5, Informative)

      by MillionthMonkey ( 240664 ) on Wednesday February 27, 2008 @01:32AM (#22569654)
      They thought for a little while that the Earth might just make it, but now it's pretty clear to everybody that's not going to happen.
    • This is the way I was taught it would happen on astronomy shows from the 1980s. I don't get the big deal.

      I read about it in a 1960's science book.

    • Re:This is news? (Score:5, Informative)

      by beadfulthings ( 975812 ) on Wednesday February 27, 2008 @02:45AM (#22570164) Journal
      Carl Sagan in his 1980 pop-astronomy series "Cosmos." He was quite poetic, talking about one "last, perfect day" for Earth as we know it as the sun begins its changes. 'Twas quite a hit in its day, that series (and book).
    • by iamlucky13 ( 795185 ) on Wednesday February 27, 2008 @04:02AM (#22570556)
      Back in the 60's or so they figured out the whole red giant phase of stellar evolution and realized the sun would expand to about the diameter of the earth's present orbit when it reached this point. It was a fascinating bit of trivia for Carl Sagan and the common folk to pass around that the sun would engulf the earth, but further investigation showed the sun would likely lose something like 30% of it's mass as heat from helium fusion blew away the outer layers (a process that looks really freaking cool [] from a distance). This would cause the earth, due to conservation of its orbital energy, to assume a much larger orbit...about as far out as Mars is today.

      Therefore the popular notion was thought by many astronomers to be wrong. But in fact, nobody had ever done a really detailed model of the process until the subject of this article. It turns out, the professionals were wrong, and the common folk were correct, if only because we were a couple decades behind the times academically.

      If you don't believe me, here's the archived wikipedia page for earth [] from last Friday. It's since been updated.
      • by Latent Heat ( 558884 ) on Wednesday February 27, 2008 @10:47AM (#22573186)
        What is this business about helium fusion in the red giant phase?

        Unless there are some revisions in the laws of physics, the nuclear processes throughout stellar evolution are well known based on computer models.

        When helium "ash" accumulates in the core, helium fusion is not the next thing that happens. The core starts contracting and heating up, but that lights off H2 fusion in the shell surrounding the core. That phenomenon changes the luminosity and heat transfer rates of the star, causing the outer atmosphere to swell up into the red giant stage.

        When shell burning runs its course, again the core contracts and heats up some more, resulting in the helium flash. Based on computer models, the helium flash is a major disruptive event caused by the sudden onset of helium fusion, it does not cause the star to go nova or anything, but it causes the star to change modes as it were, becoming somewhat bluer and smaller, but still more luminous than Main Sequence. From the computer models, it is believed that the upper-righthand HR diagram stars, red giants, are H2 shell burners while the horizontal branch above the Main Sequence represents He core burners.

        For a massive enough star, exhaustion of core He will initiate shell He ignition, sending the star back into the red giant range, perhaps as a red supergiant for a massive star.

        The red giant phase is only one phase of an evolved star. Everyone just kind of assumed that a star that goes supernova would be a red giant, but it seems like the star that popped off in Supernova 1987a in the LMS was blue.

  • by bendodge ( 998616 ) <{bendodge} {at} {}> on Wednesday February 27, 2008 @01:09AM (#22569458) Homepage Journal

    But the day of the Lord will come as a thief in the night; in the which the heavens shall pass away with a great noise, and the elements shall melt with fervent heat, the earth also and the works that are therein shall be burned up.
    (Wow! All my karma just went sailing past!)
  • As long as I've been alive, this has been pretty much the inevitable conclusion. Was there a turnaround in the cocaine infested 80s perhaps that we missed, or have since forgotten?

    By the way, this is even in New Zealand, waaaaaaay down at the bottom of the globe (not far enough down that we'd be safe from this, however)

    • No, it is the cocaine induced renaissance, after the pot induced dark ages.
    • Re: (Score:3, Informative)

      by Cecil ( 37810 )
      Only by laypeople, as far as I know. For as long as I can remember in modern astronomy, it's been thought that the Earth (as in the big hunk of rock, not any of its fancy accessories like say, life, or water... minor but important point there) would actually survive, barely. Scientists generally believed the mass loss from the inflating, overpressured sun losing its grip on its outer atmosphere would be sufficient to allow Earth to escape destruction as its orbit would be slowly spiralling outwards while th
  • This isn't news at all, in fact I haven't heard anyone say it would happen any other way. I think I have a "My First Picture Book of the Planets" that says the same thing.
  • Shit. (Score:5, Funny)

    by jerryasher ( 151512 ) on Wednesday February 27, 2008 @01:11AM (#22569480)
    And to find this out the day I discover my paxil/zoloft/venlafaxine does nothing.

    Beer me.
  • Armageddon (Score:5, Interesting)

    by gummyb34r ( 899393 ) on Wednesday February 27, 2008 @01:15AM (#22569498)
    In 7.6 bln years time frame there is a 99.9 probability of a massive object hitting Earth and melting the outermost solid shell.
    • Re: (Score:2, Insightful)

      by Anonymous Coward

      In 7.6 bln years time frame there is a 99.9 probability of a massive object hitting Earth and melting the outermost solid shell.

      It's certain that it will happen at least 9 times and 90% certain that it will happen 10 times? Or did you mean that there is a 99.9% probability or a .999 probability?

    • I would place my wager on this happening first... []
    • Re: (Score:2, Interesting)

      by Bega ( 684994 )

      Reminds me of this meteorite collision animation []; not realistic, but interesting nonetheless.

    • Re:Armageddon (Score:5, Insightful)

      by Tablizer ( 95088 ) on Wednesday February 27, 2008 @03:21AM (#22570330) Journal
      In 7.6 bln years time frame there is a 99.9 probability of a massive object hitting Earth and melting the outermost solid shell.

      Where do you get these numbers? They appear suspect. We've gone more than half-a-billion years with *no* impact strong enough to wipe out the primary phyla of animals. That would suggest that mega-impacts are not near as likely as you say.

      True, we may be in for some nasty human-ending impacts though, but not necessarily "outer shell melting", at least not the entire shell.

  • Discovery Channel, History Chanel and National Channel all show the same scenario of the sun expanding to and past earth.
    • The ancients assumed (believed) the sun is a giant camp fire. Then Einstein came along with his famous equation and humans built a hydrogen bomb. So then the solar campfire was upgraded to a thermonuclear fire. That's what we assume (believe) today.

      Thermonuclear reactions produce lots of neutrinos. However, the number of those little particles we actually measure and how many we should be measuring if indeed the sun is a giant controlled fusion reactor, is way different. The number we measure is far too sm
      • The solar corona problem isn't tied to fusion per se, just to a very hot core cooling radially outward. Also, there aren't any problems with thermodynamics in this situation provided there is some mechanism that is adding energy to the plasma at the solar surface. Given the violent nature of the solar surface, particularly with respect to solar flares and coronal mass ejections, there are certainly energy generating processes going on, so it isn't too terribly surprising that the corona gets heated up. T
      • the core of the Sun is more like 15 million degrees.

        the coronal heating problem simply means the mechanism responsible for the increased temperature is a non-equilibrium process. the corona is also a near-vacuum so despite its high temperature there is relatively tiny amount of energy there.
  • Seems easy enough. (Score:5, Insightful)

    by jd ( 1658 ) <> on Wednesday February 27, 2008 @01:18AM (#22569542) Homepage Journal
    Accelerate Earth to put it into a wider orbit. This will solve Global Warming and the Earth being swallowed all in one.
    • by RuBLed ( 995686 )
      Let Chuck Norris fart in the sun's general direction.. That should do it..
    • Accelerate Earth to put it into a wider orbit. This will solve Global Warming and the Earth being swallowed all in one.

      We just need to get all the robots to vent their exhausts in a single direction. We can use nuclear winter to cancel out global warming.

  • I was looking for something to mod up but all the replies so far are about how they learned the earth would be engulfed and surprised at the debate. I think the confusion is arises because there is no debate about whether the sun will expand to the size of earth's orbit. The debate is whether the earth will have moved far enough from that current orbit to not be engulfed. Here we go, wikipedia says precisely this:

    While it is likely that the expansion of the outer layers of the Sun will reach the current position of Earth's orbit, recent research suggests that mass lost from the Sun earlier in its red giant phase will cause the Earth's orbit to move further out, preventing it from being engulfed. []

    And some of the academic references are actually a decade old: []
  • Gravity Assist (Score:2, Redundant)

    by EEPROMS ( 889169 )
    This disaster can actually be compensated for to some degree by moving earths orbit further out from the sun using gravity assist. What you do is capture a large mass be it a comet or a large asteroid then put it in elongated orbit around earth. As the large mass now circling nears earth it pulls on the planet thus moving it ever so slightly. Few billions year later and earth has moved far enough out to avoid annihilation for a few extra billions years.
  • By that time... (Score:4, Insightful)

    by okmijnuhb ( 575581 ) on Wednesday February 27, 2008 @01:40AM (#22569738)
    ...humans will have destroyed it, and several others...
  • by michaelmalak ( 91262 ) <> on Wednesday February 27, 2008 @01:45AM (#22569774) Homepage
    After 7.6 billion years, it's time to move out of mom's basement.
  • No problem (Score:4, Funny)

    by PPH ( 736903 ) on Wednesday February 27, 2008 @01:47AM (#22569788)

    By that time, mankind will be sufficiently advanced to relocate to an outer Pluto.

    What? Pluto isn't a planet anymore??

    Oh No! We're doomed!!

  • It will also expand, driven by helium fusion so that its outer layers reach past the earth's current orbit.

    Out of shear boredom, I decided to do some calculations, using the following (someone please fix my math, if it's wrong):

    Avg. distance from Earth to the Sun (according to Wikipedia []) = 1.496x10^11 meters
    Current mass of the sun (according to Google []) = 1.9889x10^33 grams
    Current Diameter of the sun (according to Google []) = 1.4x10^9 meters
    Volume of a sphere = (4/3)(r^3)
    Density = mass/volume

    Based on tha

    • Oops... Throw a "pi" up there into the Volume equation.
    • by Einer2 ( 665985 ) on Wednesday February 27, 2008 @02:25AM (#22570020)
      I doubt if this post is high enough to net any karma, but oh well. I'll chalk it up as my outreach for the day...week...year...something. The important quantity isn't the average density, but the core density (as fusion only happens near the core). As stars evolve off the main sequence, their outer layers may expand, but they also become much more centrally condensed.

      During the hydrogen burning phase, inert helium gradually builds up in the core and hydrogen becomes less common. This means the core has to contract and become hotter in order to produce enough energy to support itself and the surrounding envelope. The fusion rate depends on the square of the hydrogen density (since you need the hydrogen atoms to collide with each other), so if the hydrogen density goes down, the core has to become hotter and more generally dense in order to maintain the same energy production rate. (This is why stars gradually become more luminous over their main sequence lifetime, as the core actually has to produce more energy in order to support itself in its more compact configuration.)

      As a star finishes exhausting its hydrogen, this actually reaches a very extreme configuration where the core becomes much more compact (and much hotter) trying to squeeze out the required energy with very little hydrogen remaining. The total energy being produced by the core (in order to keep itself from collapsing) increases very rapidly at this point, and the larger luminosity will then push the envelope outward, puffing it up. This is why stars expand into red giants, and this is the stage where the Earth will probably be engulfed.

      For trivia purposes, the central core eventually runs entirely out of hydrogen and sits there as an inert clump while the upper edges of the core burn hydrogen. When the hydrogen is exhausted for a large enough fraction of the core, the center eventually becomes hot and dense enough to fuse helium into carbon. At this point, the overall luminosity drops again (because the star doesn't need to keep frantically burning just hydrogen to support itself) and the star contracts a bit. The process then starts over again, with a shell of helium fusion surround an inert carbon core that (for stars more massive than the Sun) eventually ignites to fuse into neon, oxygen, etc.

    • by dido ( 9125 )

      From what I know, nuclear fusion happens only inside the core of a star. What happens when the sun reaches its red giant phase is that the core shrinks to maintain the pressures needed to sustain helium fusion. The sun itself may become less and less dense but the core at the center where fusion takes place gets more and more dense. The sun growing to such a large size is simply the first phase of the sun's gradually shedding off its outer layers.

  • how long the human race will survive. (no smiley)

    While I have all my life shared the deep desire to know the "ultimate end" (if there even is such a thing), the more I pay attention the more I feel the cognitive resources spent on these kinds of calculations are almost shameful - the astrophysical equivalent of gunning down buffalo from the back of the train.

    If we weren't trying to solve these problems I'd be the voice saying that we should. It was just that in a world of such instability, in reading this
    • While I don't believe the singularity will happen in 20 years, it's reasonable to believe it'll happen in less than 1,000 years.
      Thus, in a couple billion years, we can either download our minds into probes or we'll have been replaced by robots or something like that. In any case, clinging to a physical existence will be considered highly overrated.
      Or we'll just have killed ourselves off in some way and some other species can scratch their heads about it. 70-something million years for mammals to evolve into
  • In about 2 billion years the Milky Way could already collide with the Andromeda Galaxy [], which will more than likely change earth's cozy equilibrium that enables human life in a sub-optimal way.
  • Uhmmm, next how about posting something that is actually news ok? I mean for fucks sake I learned this in grade school and that was over 35 years ago!/p

  • It has been reported from archeologists who have teleported from the future to our time that 7.59 billion years from now, Duke Nukem Forever is released to manufacturing.
  • by AbsoluteXyro ( 1048620 ) on Wednesday February 27, 2008 @02:25AM (#22570030)
    When speaking of planetary catastrophe the death of our Sun is but a distant worry. It has already been mentioned that in about 3 billion years the galaxy Andromeda will collide with our own Milky Way galaxy. That of course poses several dangers to Earth in itself, though none particularly likely due to the vast distances between stars within galaxies, the potential for a stellar marauder to interfere with our solar system and cause chaos for Earth does exist. More worrisome, though, is the fact that around the same time (3 billion years from now) the Earth's core will finally cool and it's magnetic field generating dynamo will shut down, causing the Earth's shielding from the solar wind to collapse and the atmosphere to be stripped away eventually leaving the planet as dry and barren as Mars. Well before that ever happens, Earth will have to deal with the solar system's bobbing and weaving in and out of the galactic plane, possibly exposing the planet to deadly cosmic rays. Even nearer to our future is the fact that a conveniently aimed gamma ray burst from an exploding star (Betelgeuse is ready to go any day now) could "sterilize" the planet. Then of course, there is the ever present threat of an Earth shattering asteroid impact, which happens every 100 million years or so on average... in which case you could consider Earth overdue for another one. So yeah... the Sun engulfing the Earth (or what's left of it) 7 billion years from now... I wouldn't sweat that one.
    • Oh my fsm (Score:2, Offtopic)

      by symbolset ( 646467 )

      This is the most informed and educated post I have seen on slashdot for some time.

      Mod parent up! Long before solar expansion is an issue the earth will have been struck by extinction level asteroids multiple times.

      This is a test: Escape your planet of origin or die out. End test.

  • by Detritus ( 11846 ) on Wednesday February 27, 2008 @02:29AM (#22570054) Homepage
    According to the professor who taught my astronomy class, the Earth's climate will be tipped into thermal runaway, like Venus, long before the Sun becomes a red giant. Solar output increases steadily as the Sun ages. It's only a matter of time, like a few billion years, before it overwhelms the Earth's ability to regulate its temperature.
  • WTF.....? (Score:2, Insightful)

    How in the Hell is this NEWS?! Astronomers have known about this for DECADES!

    What's next? An article telling us gasoline is flammable?

    Somebody please tag this noshitsherlock.
  • I thought it said 7.6 million at first.
  • Of course, if we're still here politics would prevent moving the earth [] until it's too late.

    I mean, sure, the sun "looks" larger but is it really?

    I've got 10 industry funded studies that says it's an optical illusion.

  • I sure hope they figure this out soon.

    Should I spend a bunch of money to freeze my corpse for later revival, or would I just be throwing that money away?

    • Science may cure death for the few. For the many is a more difficult question.

      If your estate can sustain your corpse reliably for 200 years then improvements in medical science can be a fair bet. If your estate can endow a foundation to provide for your arousal then it is closer to a sure thing. Nothing is certain though. In 40 years the concept of ownership of property can vary considerably.

      In the term TFA is speaking of nothing can save you on this planet. Y(our) only hope is to escape this solar s

  • by jmv ( 93421 )
    Someone tell B.W. Bush he needs to invade the sun to get rid of its WMDs.
  • >A minor academic debate among astronomers is the final fate of the earth.

    I don't know, but I bet the Cylons will have something to do with it.
  • At least this way, all that plastic garbage we've churned out finally gets recycled.
  • "A minor academic debate among astronomers is the final fate of the earth" - in 7 billion years.
          However, a major debate is the final fate of the Universe - will it expand indefinitely, leading to the thermal death? Or it will be crushed together by the force of gravity, in a reverse of the Big Bang? This might take a little longer than 7 billion years
  • This is old news (Score:3, Insightful)

    by SystematicPsycho ( 456042 ) on Wednesday February 27, 2008 @08:35AM (#22571868)
    We learnt this in science in the 80s. It's probably older news than that. So what if there is a new calculation, does 7 billion years away really matter?
  • by Kinthelt ( 96845 ) on Wednesday February 27, 2008 @09:56AM (#22572524) Homepage
    If evolution is a myth, what chance does gravity have? It is also, after all, only a theory.

"I prefer the blunted cudgels of the followers of the Serpent God." -- Sean Doran the Younger