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Colliding Worlds: The Ultimate Extinction Event

When Worlds Collide, the 1932 novel of planetary catastrophe, presented the most extreme extinction event imaginable. A pair of wandering planets enters the Solar System, one on collision course with the Earth, the other destined to be captured into orbit around the Sun. The doughty crew of an escaping rocket, on their way to a new life on the captured world, can only watch in horror as the Earth is destroyed.

Now we learn about a ‘when worlds collide’ scenario that seems to have involved two mature, Earth-sized planets in a distant Solar System. The system in question is BD+20 307, originally thought to be a single star with a massive, warm dust disk, but now known to be a close binary orbiting the common center of mass every 3.42 days. Both stars are similar to the Sun in mass, temperature and size. Moreover, the system seems to have an age comparable to our own Sun, and the sheer amount of dust at roughly Venus to Earth distance is quite interesting.

We would expect the dust particles to be pushed outward from the stars by stellar radiation. That they have not been indicates that the event that produced them must have occurred relatively recently, perhaps within the past few hundred thousand years. A planetary collision is inferred from the evidence of a disk with a million times more dust than is found around our own Sun, says Gregory Henry (Tennessee State University):

“The planetary collision in BD+20 307 was not observed directly but rather was inferred from the extraordinary quantity of dust particles that orbit the binary pair at about the same distance as Earth and Venus are from our sun. If this dust does indeed point to the presence of terrestrial planets, then this represents the first known example of planets of any mass in orbit around a close binary star.”

Once again we have a glimpse of how violent a planetary system can be, although destabilized planetary orbits in a mature system do seem to be rare. Henry goes on in this news release to discuss Jacques Laskar’s work in France and that of Gregory Laughlin (UCSC) and student Konstantin Batygin, whose models make it clear that planets even in our own system can go awry, with Mercury in particular prone to odd behavior if we extrapolate far enough into the future. The odds of collision are indeed small, but that also tracks with the rarity of mature, dusty systems like BD+20 307.

As to When Worlds Collide, I loved the 1951 film version of the Philip Wylie and Edwin Balmer novel as a kid, although it can only be said that the movie doesn’t age well, and a recent viewing made every bit of stilted dialog and lame character interplay all too apparent. Still, the story is captivating, and watching the team of determined scientists racing to complete a space ark in time to save at least a portion of humanity has its pleasures. I notice that a re-make is in the works, scheduled for 2010 or thereabouts. This one seems to posit a near-term collision between our system and the Alpha Centauri stars, so the odds on scientific verisimilitude don’t look good.

Comments on this entry are closed.

  • ZardozBigHead September 25, 2008, 15:33

    How come only white Americans got saved in the film version?

  • mark mixon September 25, 2008, 16:01

    i was just reading an article on Yahoo about how the leve deposite in Siberia that occured in the Permian were likely caused by the impact of a very large asteroid. Then it goes on to explain that the oldest rocks known are the zircon crystals found in Australia that are 4.4 billion years old. These were formed during the Hadean age called the dark age of the earth. This is the same time that it is tought that a planet sized object struck the earth and caused the formation of the moon.

  • Adam September 25, 2008, 19:22

    Hi Paul

    Another possibility is that the dust derives from the heavy element cores of two gas-giants. Michael Woolfson’s SPH simulations of such show they can actually form terrestrial planets from the remnants.

  • James M. Essig September 25, 2008, 21:18

    Hi Folks;

    This is an interesting thread.

    It really causes one to wonder what would happen if a planet sized Kuiper Belt object or Oort Cloud object had Earth’s name on it at some point during the next few decades to centuries. A perhaps more scary though would entail a brown dwarf interloper entering our solar system and totally destabilizing the orbits of all of the known planets. A white dwarf or should I say black dwarf entering our solar system perhaps on collision course with the Sun would be scarier yet. Worse yet would be a solar system interaction with a neutron star perhaps on collision course with the Sun followed by the entrance into the solar system of an undetected very mildly relativistic mid range massed black hole, perhaps with the mass of 1,000 to 10,000 solar masses.

    We could even imagine a nearby universe expanding through or traveling in hyperspace running into our universe, perhaps with the initial zone of impact being located within our observable universe.

    Worse yet could be the remote chance of a Big Bang occurring within our universe and not becoming casually or existentially decoupled from our universe, nor decoupled in the space-time-mattergy sense, with a probability of 1/(infinity) or dP where dP is the differential element of the line segment from 0 to 1 defining the possible range of probabilities and wherein the value of probability dP is essentially equal in magnitude to the high school or first year college calculus concept of dx.

    The fact that our universe has not yet experienced such an event might be due to the fact that the probability of such an event is so close to dP. In the event that our universe is infinite in spatial extent, with a total of an infinite amount of zero point vacuum fluctuations occurring in every finite time unit interval, the risk may still present itself because the actual probability of a big bang or even of a fractal verse starting within our universe and becoming enmeshed within it might be equal to 1/[n(Aleph 0)], 1/(Aleph 1), 1/[n(Aleph 1)], or 1/(Aleph 2) wherein Aleph 1 and Aleph 2 are sequentially higher Cardinalities than Aleph 0 which is the number of integers or the lowest cardinality and n is some very large finite number. Thus the risk of such a catastrophe may still present itself.

    At the very least, the inherent uncertainly of the occurrence of ever larger catastrophes might still appeal to our collective morbid sense of excitement. Although I do not really enjoy catastrophes, in fact I always pray for the victims of such, including and especially those who die, even the looming presence of large hurricanes keeps me glued to the TV. There is something primal within our makeup by which we become energized by the possibilities of risk.



  • Administrator September 26, 2008, 8:10

    Adam wrote:

    Another possibility is that the dust derives from the heavy element cores of two gas-giants. Michael Woolfson’s SPH simulations of such show they can actually form terrestrial planets from the remnants.

    Interesting! Do you have a reference for Woolfson?

  • andy September 26, 2008, 8:12

    How come only white Americans got saved in the film version?

    Because it was made in the 1950s. If it were made today, the one token black guy would get saved.

  • ljk September 26, 2008, 11:12

    You know, Paul, if our Sol system is going to collide with the
    Alpha Centauri system, that will certainly save us the bother
    of hainv to build a starship and send it all the way there.

    I can’t believe they have also remade the classic 1951 SF film
    The Day the Earth Stood Still. What I have read about it does
    nothing to improve my view that it is both unnecessary and far
    inferior to the original.

    What next, a remake of 2001: A Space Odyssey? OOPS!

  • andy September 26, 2008, 14:32

    Well, it might be that the system around BD+20 307 just happens to have had an instability that took a billion years or so to work itself out. Alternatively, someone’s been on the receiving end of a relativistic missile strike…

  • ljk September 26, 2008, 20:20

    I know, Andy – My modern sensibilities compelled me to
    at least say something.

    Now, what are the odds that two planets would come
    crashing through our Sol system, one to hit and destroy
    Earth, while the other goes into a nice orbit that is JUST
    RIGHT for human habitation.

    Plus there were the signs of a previous civilization on it:


    And what could have caused those planets to get flung
    out of their solar system to begin with? An accident of
    chance, or… intelligent design?