When worlds really do collide!

By Phil Plait | August 24, 2010 6:30 am

When I was a kid, one of my favorite movies was "When Worlds Collide", about a rogue planet that collides with Earth, killing everyone (except for a few who escape on rockets).

Science fiction, right? Right?

Yeah, maybe not so much. It turns out, worlds really do collide. And we can see the shrapnel.

spitzer_planet_smash

Binary stars are stars that physically orbit each other. They’re extremely common, but there are many types. One special kind are where the stars are very close together, like only a few million kilometers apart. Note that your average Sun-like star is well over a million kilometers in diameter, and you’ll appreciate that’s a pretty tight pair.

Not only that, but there’s a further subgroup of these binaries called RCVn (short for R Canes Venatici, the star that serves as the prototype). These are older stars, where at least one of the pair has swollen up as it begins to become a red giant. In these cases, tidal evolution has forced the stars to rotate at the same speed they orbit each other, forever showing each other the same face.

spitzer_binary_rcvnAstronomers used the Spitzer Space Telescope to observe 10 such close-knit pairs. What they found was surprising: three of the stars showed a significant excess of infrared light. We know how much IR these kinds of stars should give off, and these three systems were clearly overachievers.

What could cause that?

Typically, when we see a star with too much IR, it means it has lots of dust around it. Dust warmed up by the star will emit IR, adding its light to the star’s. That’s seen quite a bit around young stars. But these RCVns are old, really old. Where would their dust come from?

Yeah. Check the title of this post.

As the two stars orbit each other, they shed mass through a stellar wind, like the Sun’s solar wind. As they lose mass they get closer together, and that changes their gravitational effect on any planets that might orbit them (and we have detected planets orbiting tight binary stars). This shifts the planets’ orbits, and no good can come of that. In fact, as the orbits shift so much they can cross each other, and can cause the planets to collide.

The energy in such a collision would dwarf the sweatiest nightmares of any Hollywood writer — or religiously-motivated apocalyptic preacher, for that matter. The two planets, each massing sextillions of tons, would ram each other at speeds of 20 or more kilometers per second. The energy released would be trillions of times that of all our nuclear weapons combined.

What would that look like if you were standing on one of those planets?

Imagine: the twin suns, so close they appear to almost touch, set toward your western horizon. As dark rises to the East, so does the rim of a vast disk. After an hour, it clears the horizon: a disk of light in the heavens so bright you have to squint, and so big it spans half the sky. It’s a rogue planet, and only a year before it was barely more than a brilliant point of light in the sky. Now it looms so large you feel you could fall into it.

A strong earthquake shakes the ground as they have for the past few days; the result of the titanic tidal stress induced on your planet from the other’s gravity. On the other planet, with your naked eye, you can see networks of hundreds of massive cracks lit dull red from magma, the tides from your home world stressing and tearing apart the interloper. The disk grows as you watch, blotting out the majority of the sky by the time it sets a few hours later.

The suns rise, and happily you’re on the side of the planet facing away from the location where the two worlds will touch. You’re spared the actual sight of the catastrophe.

Not that it matters, really.

When the shock wave from the collision finally reaches you, it marches across the landscape like a mighty god, like an angry god, like a hungry god, destroying everything underneath. What follows is an earthquake literally too large to measure: one that rips out the top hundred kilometers of the planet, totally removing the crust, and utterly wiping out billions of years of planetary and biological evolution.

It takes hours, but when it’s done, the two planets are gone. They are smashed, pulverized, surrounded by an expanding cloud of billions of gigatons of vaporized rock that’s sent sleeting out into space. Some time later, what’s left is a white-hot sphere — the merged remains of the cores of the two worlds — surrounded by glowing debris, boulders the size of moons, and enough dust to choke the entire planetary system for millions of years.This dust forms a disk around the star… and a few hundred light years away, we would see it as a blip of extra infrared light.

Perhaps this scenario lacks the hero-destroys-the-evil-villain of a good space opera, but it does have the advantage of being real. Still, "When Worlds Collide" was pretty close! And "Star Wars" had the right idea… but the wrong planet. Alderaan was Princess Leia’s home, which was utterly destroyed by the Death Star. Tatooine, however, was a planet orbiting two stars apparently in a close orbit… and now we know how that turns out.

Artist illustration credit: NASA/JPL-Caltech

Comments (72)

  1. Messier Tidy Upper

    Wow! :-D

    Well written BA. This. Is. Awesome! :-) 8)

    Imagine: the twin suns, so close they appear to almost touch,

    Also imagine here the two stars are so close their shapes have become distorted – not spherical but ellipsoidal or egg shaped. Imagine squeezing the Sun into a white hot elongated grape in the sky – then doubling it in a mirror image like a white hot filled infinity symbol rising, setting and moving across the sky.

    Also each star will be pock-marked with huge starspots and violent stellar activity making them slightly variable as their clashing magnetic fields protest the enormous strains of being forced together into lockstep.

    Eventually these binary stars will actually merge – look at FK Coma Berenices stars.

    One such actual system – ER Vulpeculae – which is composed of two close analogues to our Sun that are in such a situation (& will eventually merge to form one Sirius like A type star), featured in an article “Dance of the Double Sun” by Ken Croswell in Astronomy magazine, July 1993 (Kalmbach publishing Co.) The artwork for that was breathtaking but I’m sure doesn’t even begin to approach the real scene.

  2. Your doomsday scenarios are almost poetic. I love them!

  3. Awesome! Although this sentence doesn’t quite make sense:

    “We know how IR these kinds of stars should give off”

    I think you meant ‘how much’ ?

    The mental imagery that scenario conjurs up sent a little chill down my spine…

  4. I’d be happy to watch a feature length movie that is just realistic depictions of what real life astronomical phenomenon looked like up close.

    And not to flaunt my nerd knowledge but Star Wars actually already did this. Chewbacca dies, howling defiantly, as he’s crushed between a planet and it’s moon.

  5. Jack Mitcham

    Very well-written vingette, Phil. Have you ever considered writing a book or something? Maybe you could do a book with one of those scenarios before every chapter. Or at the very least, do a book about bad astronomy.

    :-p

  6. DrFlimmer

    Well, this sounds a like a way the world will end!

    Phil, you should write a book about it! ;)

  7. Doesn’t red giant formation also involved dredge-ups and dust creation as the star blows off outer layers?

  8. Messier Tidy Upper

    One stage in this process is the type of variable star exemplified by Sheliak or Beta Lyrae :

    http://stars.astro.illinois.edu/sow/sheliak.html

    with the brightest example being Spica! (See on Kaler’s Site too.)

    For FK Comae / FK Coma Berenices stars see :

    http://en.wikipedia.org/wiki/FK_Comae_star#FK_Comae_Berenices_variables

    & see this paper for more about ER Vulpeculae :

    http://aa.springer.de/papers/7318001/2300060/sc2.htm

    Incl. a note that :

    the presence of extended material around ER Vul which is suggested by some studies is yet to be confirmed spectroscopically.

    Hmm … Behind the dry words there, an astonishing picture is growing. :-)

  9. Messier Tidy Upper

    Oops, I almost forgot to add that the close contact binaries are also termed W Ursae Majoris stars after a significant example of this variable class.

    So for more look up W Ursae Majoris stars, contact binaries & FK Comae Berenices stars – these form a progression of binary stars that are merging with the stages running as follows :

    1) Start with a very close binary stellar pair – eg. RS Canum Venaticorum (or perhaps Spica) After a while they will be tidally locked and conserve their angular momentum by spiralling inwards until ..

    2)These stars meet to become contact binaries like W Ursae Majoris the prototypical example of two stars in the process of fusing together, stars that have spiralled in together until their surfaces are in contact. The process continues as gravity and angular momentum continue to conspire to ..

    2)Fully merge the two stars into one FK Comae Berenices being the prototype here – a weirdly spotted highly active fast spinning single stars – that used to be two stars.

    Source: James B. Kaler’s book, ‘The 100 Greatest stars’ Copernicus books, 2002.

    [FK Comae Berenices is on page 82-83 star 40, & W Ursae Majoris is pages 198-199, star 98 therein.]

    Plus as noted earlier, if you can find a copy somewhere there’s a great article “Dance of the Double Sun” [ER Vulpeculae] by Ken Croswell which has awesome accompanying space art by illustrator Michael Carroll in the July 1993 issue of ‘Astronomy’ magazine. Pages 27 to 33 & cover illustration. That article discusses the variable star and close binary or contact binary ER Vulpeculae which is a pair of G1 & G2 class dwarfs – remarkably like our Sun! Or is until it finally fuses completely & then it will become more like a hyperactive spotty version of Sirius! (Well Sirius A anyhow. ;-) )

    From that article Ken Croswell notes :

    “Roughly one in every thousand stars is a contact binary so our galaxy is full of these exotic objects. The ..nearest contact binary is 44 Bootis B which lies a mere 38 light years away. …ER Vulpeculae has raised the slim possibility that our own Sun was once a contact binary.”
    – Page 33, Croswell, July 1993.

    Pretty amazing huh? Our Sun might have begun its stellar career as not one but two half solar mass twins and we may never know it! Hope folks find this interesting / useful. :-)

  10. Messier Tidy Upper

    @6. Lab Lemming Says:

    Doesn’t red giant formation also involved dredge-ups and dust creation as the star blows off outer layers?

    Yes indeed – most notable in the sooty disappearing R Coronae Borealis variables.

    We’ve also had cases of dust from broken up comets detected around white dwarfs too.

    But these are different cases again.

  11. Chris

    Perhaps someone can help me here. I remember seeing this movie over 20 yrs ago on TV probably made in the ’60s or ’70s. A rogue planet was going to collide with Earth and they made Australia into a giant rocket engine to move the Earth out of the way. In the end the rogue planet just passes by and Earth is saved. I guess they totally forgot about gravity that would have flung the Earth out of orbit. I’ve tried Googling for the name of the movie but can’t seem to find it. I’d appreciate it if anyone remembers. Thanks

  12. Messier Tidy Upper

    For more on the “reverse nova” R Coronae Borealis see :

    http://en.wikipedia.org/wiki/R_Coronae_Borealis

    For more on the White dwarf with planetary remains around the stellar corpse see :

    http://www.universetoday.com/11652/dead-star-found-polluted-by-earthlike-planet/

    or Wiki GD 362.

    Oh & some folks here may recall this BA blog post from a few years ago :

    http://blogs.discovermagazine.com/badastronomy/2008/12/12/dim-faint-and-small-is-no-way-to-go-through-life-son/

    Noting the (then?) dimmest “stars” ever found – a pair of brown dwarfs – 2M0939 – were found as a very tight binary which will, presumably or at least possibly, also go through the process noted in comment # 8 above with some (ahem) familiar discussion of the tight binary -> stellar merger phases in comments #54 down.

    (Yes I used to be ‘StevoR’ back then & yes I’ve cut & pasted & edited. Hope that’s okay! ;-) )

  13. kevbo

    Wow. I can hardly wait to see you narrate this scenario from the CGI surface of the doomed world on an upcoming episode of your Sooper Sekrit Project ™!

  14. @ Chris:

    Might that have been Gorath, a Japanese monster flick from 1962?

  15. Gary Ansorge

    New book title;

    “The Dance of Stellar Death”,,,unfortunate, it is, that this can also apply to Hollywood.

    I’m visualizing two stars smacking into one another head on. Bet that would be something to see,,,from VERY far away.

    (Dang! I just saw(mentally) Tom Cruise head butting Adam Baldwin,,,and losing.)

    Gary 7

  16. I’ll admit, I’m a little unhappy I didn’t have a chapter on this in the book. Seems obvious in retrospect. But then, three years ago when I was writing it we didn’t know about this scenario. But we do know planets get tossed around as systems evolve.

  17. Chris

    @ kuhnigget – Thank you!
    Actually reading the description, I think that could actually be it. It’s not easy trying to remember some movie I probably saw on a Saturday night when I was 8. But moving the Earth out of the way using rockets was one of those “bad astronomy” moments which really stuck with me.

  18. ethanol

    I would think that the stars losing mass would just move all of the orbits outward, but I can see how orbiting two stars, even if they were quite close, would introduce unpredictable gravitational effects on the orbiting planets

  19. I would love to see a film that depicts the entire events of a world ending collision. I mean one that accurately depicts the events. I’m not talking a Hollywood its-ok-Bruce-Willis-will-save-us type of movie. Just a non-biased multi-angle view of the awesome spectacle that is two worlds obliterating one another.

    I’d pay to see that on the silver screen! Since, witnessing it in any real life fashion means that you’re pretty much doomed.

    And for bonus materials? Show other collisions, such as head-on, glancing, t-bone (side swipe, if that’s even possible?), etc. Since it’s not a ‘one size fits all’ Universe, ya know?

  20. SteveM

    I am disappointed there was no mention (even if just in passing) that the Earth/Moon system is very likely the product of a similar planetary collision that was lucky enough to be a “glancing blow” rather than head-on, but still pretty devastating to the original Earth and the Mars sized planet that collided.

  21. Merijn

    Now what would happen if the rogue planet came only rather close by, I’d guess that a Mars-sized object passing within, say, 1 Lunar distance (approx 400.000km) would cause rather a stirr.. that that’s about a few dozens of times more likely.

    Luckily, our Sun happens to be a fairly calm and lonely thing, and with Jupiter catching quite a few bullets we’re rather safe here.

  22. Derek

    Sounds like fodder for an episode of Bad Universe :)

    What kind of explosion would you need to model a planetary impact…? Oh, you’re saying that’s not the way you would approach testing it? Well, maybe you can do some cool stuff with model planets in a vacuum chamber, then.

  23. David C

    Whew… that was exciting!

  24. Captn Tommy

    In When Worlds Collide, the Worlds actually miss each other, but the gravitational havoc is well illustrated, The Rocket Ark, was built in a stable location on the earth – like the Canadian Plate – so survives the earthquakes (academy Award winning as I recall). The other world passes by and the Earth actually plunges into the star.

    Good movie, the book is better. Your tale is scary.

    Captn Tommy

  25. colin

    Reminds me of Asimov’s book Nightfall.

  26. merbrat

    When Worlds Really Do Collide!

    Showing nightly, at Milliway’s
    Worlds Famous Restaurant at the End of the Universe!
    (be sure to tip your waitstaff)

  27. Messier Tidy Upper

    @24. Captn Tommy :

    The Rocket Ark, was built in a stable location on the earth – like the Canadian Plate – so survives the earthquakes (academy Award winning as I recall).

    An earthquake won an academy award? I bet its voice was shaking and the ground moved when it gave its acceptence speech! ;-)

    ***

    @20. SteveM : Pluto also endured a similar collision that led to the formation of Charon, Nyx and Hydra or so I gather.

    Also I think I read somewhere that the explanation for why Mercury has such a relatively large core versus mantle ratio is that a lot of that planet was blasted off in a colossal impact that stripped away much of our systems innermost world’s outer layers.

    So yeah, our early solar system = a time with a *lot* of really large impacts.

    ***

    @11. Chris Says:

    Perhaps someone can help me here. I remember seeing this movie over 20 yrs ago on TV probably made in the ’60s or ’70s. A rogue planet was going to collide with Earth and they made Australia into a giant rocket engine to move the Earth out of the way.

    I don’t recall that movie I’m afraid, but that does remind me of a Futurama episode where all the robots (condemned to perish so we may live by Nixon’s head) cure cure global warming by moving the Earth by venting their exhausts together from a small island and thus save themselves from destruction – the one where Bender can’t roll over from his back but then finds he can inspired by a tortoise .. ;-)

  28. SLC

    In the novel, “When Worlds Collide,” written in 1934, there were two planets arriving from outer space discovered by a South African astronomer named Bronson. Bronson Alpha was a jovian type gas giant planet around which revolved Bronson Beta, an earth-like planet. Bronson Alpha wiped out the earth with the force of the collision somehow detaching Bronson Beta from its orbit around Bronson Alpha and setting it into an elliptical orbit around the Sun with aphelion being fairly close to the orbit of Mars. In the follow on novel published the following year, “After Worlds Collide,” we find that a total of 4 space ships made it to Bronson Beta, 2 from the US, one from Great Britain and one from Russia.. Apparently, French and German space ships didn’t make it.

    According to IMDB, a remake of the film is planned for 2012 which hopefully will not be as dreadful as the remake of, “War of the Worlds.”

    Also according to IMDB, the producer of the original film, George Pal, had planned to film a version of, “After Worlds Collide,” but he died before he was able to obtain backing for the project.

  29. So, Bruce Willis and Ben Affleck won’t save us from Armageddon?

    Hold me, I’m scared.

  30. SLC

    One can download the 1951 movie, which is available on a number of file sharing sites (e.g. Rapidshare, Megaupload, Mediafire, Hotfile, Depositfiles, etc.) and also on BTtorrent. Google is your friend.

  31. Pepijn

    People who like this kind of thing should check out the book The Forge of God by Greg Bear.

  32. Ronan

    …Goodness, our universe is an impressive place. I wonder, could a planetary system survive the chaos if the planets orbited sufficiently far away from the stars? And suppose some of the planets are already tied into close orbits around each other? Say you had a system with…well, to make it interesting, three planets. One might be a cold gas giant, orbiting VERY far away from the twin stars in the center, while the other two might be binary planets, orbiting around each other. Would those two planets be safer than if they weren’t orbiting around each other, or would their destruction be even more likely?

  33. Messier Tidy Upper

    Hmm .. this very blog reported a clash of worlds – a moon sized planet crashing into a Mercury sized one around HD 172555 back in August last year – see :

    http://blogs.discovermagazine.com/badastronomy/2009/08/10/when-worlds-collide/

    Complete with an animation.

    As for Mercury looking the way it does via major early “hit & run” impact see :

    http://www.space.com/scienceastronomy/060111_hit_and_run.html

    While at theopposite end of our solar system we had Pluto’s moons Charon being formed via impact as noted – see :

    http://www.newscientist.com/article/dn6941

    With Earth in between these extremes also copping the great Big Splash that formed our oddly large moon. ;-)

  34. Messier Tidy Upper

    Note also that the “fun” of planetary impacts in our own solar system isn’t over yet – a recent study suggested that in five billion years time or so our inner solar system could become a *very* destructive place (again) with possible collisions of Earth and Mars or Venus triggered by Mercury’s orbit getting too eccentric. See :

    http://www.globegazette.com/news/local/article_20a000b9-ee5b-5427-8d75-bcef7bc0f30e.html

    I’m pretty sure there was an article or two in a couple of astronomy mags about this too. Plus a BA blog entry on it somewhere? ;-)

    @31. Pepijn Says:

    People who like this kind of thing should check out the book ‘The Forge of God’ by Greg Bear.

    Yes and its sequel – Anvil of Stars is even better! I loved the alien “braids” in that & it’s grand ideas, plot and characters. Its a bit slow to start off with perhaps, but well worth perserving with. In My Humble Opinion Naturally. :-)

  35. andy

    Bit of a nasty way to destabilise a planetary system really: everything might seem fine for billions of years, until one of the planets ends up in a resonance with the central binary and all hell breaks loose.

  36. Utakata

    Apparently 5 minuts of Bruce Willis is saving Sylvester Stallone’s career currently, Romeo Vitelli @ 29.

    On to more serious matters though: A few odd questions.

    1) Binary stars being that close together…would they not be “egg shaped” due to their gravitational pulls on each other? Or does this “tidal evolution” effect cancel out this distortion of the stars in question?

    2) What are the chances of two planets capturing each other’s orbits instead of colliding, creating a double planet instead of rubble fodder for their orbital plains?

    3) What if either planet …or both planets had healthy size moons? I thinking of something like a billiard table of balls like collision on a massive scale…

    4) …speaking of which, would not a new planet form from all the rubble? Like our moon did from our planet did from a supposedly collision smaller planet?

    5) I noticed cgray is not claiming this to be some evil liberal conspiracy. What’s up with that?

  37. Michael Swanson

    I highly recommend taking the time to create your own 2-dimensional solar system, courtesy of the folks at the University of Colorado.

    http://phet.colorado.edu/sims/my-solar-system/my-solar-system_en.html

  38. Brian Schlosser

    And when worlds collide
    Said George Pal to his bride
    I’m going to give you some terrible thrills
    Like a —

    SCIENCE FICTION… DOUBLE FEATURE

    :D

  39. andy

    Yes and its sequel – Anvil of Stars is even better! I loved the alien “braids” in that & it’s grand ideas, plot and characters. Its a bit slow to start off with perhaps, but well worth perserving with. In My Humble Opinion Naturally. :-)

    Regarding Anvil of Stars, I tend to agree with Charles Stross’s interpretation: the picture of the universe and the role of civilisations it portrays is very, very bleak indeed. Either you get wiped out or you end up as sockpuppets in a war between various factions of world-destroyers.

  40. Navneeth

    The disk grows as you watch, blotting out the majority of the sky by the
    time it sets a few hours later.

    That was anti-climactic — in a very good way! Even though the “night time” was described in only a few lines, I had already lost myself in the alien planet and was ready to face the rogue head-on. But reading that it set after a few hours, made it a little more scarier. :) I was spared from immediate annihilation, for the moment… but the rogue’s still out there, ready to strike at any moment. [Of course, there’s no suspense. Thanks to clockwork mechanics, I’ll know exactly when it’ll hit.]

  41. Merijn (#21)

    Now what would happen if the rogue planet came only rather close by, I’d guess that a Mars-sized object passing within, say, 1 Lunar distance (approx 400.000km) would cause rather a stirr.. that that’s about a few dozens of times more likely.

    If a certain ’80s Saturday morning cartoon can be trusted, that would cause massive devastation, but not to worry, civilization would be reborn with superscience and sorcery.

  42. andy

    Also, for the sake of accuracy:

    Not only that, but there’s a further subgroup of these binaries called RCVn (short for R Canes Venatici, the star that serves as the prototype).

    This is bad astronomy and bad Latin :-)

    The class is the RS Canum Venaticorum stars (R Canum Venaticorum is apparently a Mira Ceti-type variable, i.e. a pulsating red giant star). Constellation names should be put into the genitive case when part of star designations: thus Canes Venatici (the nominative form) becomes Canum Venaticorum.

  43. Tony

    @Michael #37

    Very good site Michael. I created a binary system with one planet to see if I can get the planet to change which star it orbited. Not hard, but eventually the planet goes bye bye.

  44. Captn Tommy is right!

    The movie _When Worlds Collide_ didn’t actually have any worlds colliding in it. The planet Zyra passed close by Earth, causing quakes, but didn’t hit us. Zyra’s star, Bellus, came close enough to the Earth to catch it on fire like a cheap 1950s special effect, but we never get to see an impact.

  45. Chip

    Good writing!

    Another scenario you might explore is the possibility in such a solar system of a near miss, (which doesn’t get our planetary hero off the hook for long.) What might happen is that the two planets are flung out of their solar system or at least into wildly elliptical orbits. Moving in too close and then enormously far from the binary. After surviving all the terrible earthquakes and weird weather associated with the short near-miss event, we are treated to seasons of the coldest and longest winter imaginable (frozen atmosphere) followed by the shortest but hottest summer imaginable (molten surface).

    BTW- [bragging]My father worked for the studio that made “When World’s Collide”.[/bragging].
    My dad hoped they would make the second book, “After Worlds Collide” by Philip Wylie and Edwin Balmer into a sequel. That book, titled “After Worlds Collide” is a pretty cool story about the thawed-out alien replacement planet. Chesley Bonestell did the landscapes for the end sequence in the film of “When Worlds Collide” and hints of alien structures can be glimpsed in the far distance in the final seconds of the film.

  46. Gary Ansorge

    32. Ronan

    Your question is nearly impossible to answer at our current level of mathematical understanding,ie, we’re unable to EXACTLY calculate interactions between more than 3 ideal bodies(bodies that are exactly equal in mass and relative positions). It’s called the three body problem.

    Now, if we use a really BIG computer, we can approximate the answer, but that will take a while, since we have to calculate the positions of each object, then the effect one has on two, then two on three, then three on one and two, then,,,well, you get the picture. Which is why our space craft have to be able to correct their trajectories in flight, to correct for exactly where they are vs where the planet/asteroid/comet is going to be(w/in margins of error).

    It may be easy to hit the moon, but a fast moving asteroid/etc is another matter.

    Gary 7

  47. Chris Winter

    Chip wrote: “That book, titled “After Worlds Collide” is a pretty cool story about the thawed-out alien replacement planet. Chesley Bonestell did the landscapes for the end sequence in the film of “When Worlds Collide” and hints of alien structures can be glimpsed in the far distance in the final seconds of the film.”

    Cool! In the second novel, they find that the planet they escape to had been inhabited by an intelligent race. I dimly remember some sort of monument with an inscription that a scientist manages to partly translate. Evidently it’s about the coming doom; he calls it “Talon.”

  48. Chris Winter

    Phil Plait wrote: “I’ll admit, I’m a little unhappy I didn’t have a chapter on this in the book.”

    Second edition…

    I’ll add my vote to those wishing to see a more realistic depiction of a planet’s destruction in film. The breakup of Alderon didn’t make it; it happened much too fast.

    Dim memory number 2: Somewhere in one of E. E. “Doc” Smith’s Lensman novels there’s a scene where the good guys wipe out a planet full of chronically bad guys by setting up some sort of massively dense force field in its path. My recollection is that this collision is described somewhat accurately. But of course it’s in print, not on film.

  49. Dave

    Isn’t a rogue planet one that isn’t orbiting a star? And 20 km/s sounds high-ish (certainly not a minimum), Earth’s speed is 30 km/s and the relative velocity with a neighboring planet could be only be a small fraction of that, especially after gravitational interactions progressively bringing them closer together.

    Planetary orbits are chaotic, so a gradually evolving star could lead to a high-speed collision. But evolution of binary planetary systems and low-speed collisions might also be possible. I don’t see why those possibilities should be dismissed. I would guess that it’s the more likely outcome when each planet only has a few neighbors with which to interact. Further evolution of a clear, mature planetary system may be different from initial evolution of of a crowded disk. (And in any case, the only system we know not to contain any binary planets is our own. That doesn’t exactly prove anything.)

  50. John Sandlin

    I had a momentary flashback to Arthur C. Clarke’s “Rescue Party.”

  51. Jess Tauber

    Then there is the Bugger planet from Ender’s Game that just turns into a dust bunny floating in space.

  52. Carl

    Actually, SLC, you left out the nastiest part from the novel: Bronson Alpha and Beta flew by twice. And while the second passage took out the Earth, the first one was no cakewalk either. For this, think “2012” with lower tsunamis – 700+ ft. instead of 10,000+ ft. – but far nastier tectonic and volcanic activity (or to put it another way, count yourself lucky if you “merely” drowned that day) Plus, Alpha took out the Moon as a “light snack” during that fly-by.

  53. mfumbesi

    You Sir are a narrator of high caliber.

  54. ggremlin

    On the probability scale this scenario is way down on the chart, but how close would a rogue object(planet is so yesterday) say the size and mass of Jupiter can get before it starts affecting the Earth crust? I mean disaster type movie but survivable.

  55. Messier Tidy Upper

    @39. andy Says:

    Regarding Anvil of Stars, I tend to agree with Charles Stross’s interpretation: the picture of the universe and the role of civilisations it portrays is very, very bleak indeed. Either you get wiped out or you end up as sockpuppets in a war between various factions of world-destroyers.

    Yes, I see what your saying there – & I wouldn’t mind reading that Charles Stross analysis if you could point me to it, please. ;-)

    However, ‘Anvil of Stars’ (AoS) is still a gripping, fascinating read and ‘Anvil of Stars’ is a lot less bleak & more optimstic than, say, Pellegrino & Zebrowski’s ‘The Killing Star’ (tKS) novel or, grimmer yet, Stephen Baxter’s Titan which would have to be *the* gloomiest (if also a fascinating and well written) SF novel I’ve ever read.

    (With the possible exception of George Orwell’s 1984 if you class that as SF. *That* is just the most depressing book ever. :-( )

    ‘Bleak’ doesn’t always mean bad or depressing & AoS contains some hope and is still one of my all-time favourites despite its grim outlook on the nature of ETIs. :-)

    I guess AoS along with tKS & for that matter many others offer one rather frightening explanation to the Fermi paradox which is, sadly, rather plausible.

  56. Nigel Depledge

    Phil, you are made of Awesome!

    This makes me so glad that Earth does not orbit a tight binary star system.

  57. Nigel Depledge

    Messier Tidy Upper (54) said:

    . . . Stephen Baxter’s Titan which would have to be *the* gloomiest (if also a fascinating and well written) SF novel I’ve ever read.

    Quite possibly the most depressing SF book I have read.

    (With the possible exception of George Orwell’s 1984 if you class that as SF. *That* is just the most depressing book ever. )

    Even more depressing – it’s starting to come true. The UK has more CCTV cameras in public places per head of population than any other country.

  58. @ Nigel:

    Even more depressing – it’s starting to come true. The UK has more CCTV cameras in public places per head of population than any other country.

    And they promoted them with those very Orwellian “big brother is watching” posters that were plastered all over the bus shelters and tube stations.

  59. OmegaBaby

    Another interesting scenario is where you have two planets in a very-slowly decaying orbit around each other. For example, say the Moon was slowly getting closer to the Earth instead of moving away. If this occurred slow enough, the Earth and Moon could become tidally locked, always pointing the same face to each other. Slowly, the oceans, and even the atmosphere, would drain from the far side of the Earth and start “pooling” on the near side. You would have violent volcanoes forming on the near side of the planets as the center of gravity of each slowly move towards each other (although they’d be hidden by the immense ocean that has gathered there).
    Eventually, the Moon would gently “touch down” on the surface of the Earth, and you would end up with a weird hourglass shaped planet with a ring of ocean and atmosphere clinging to the “valley” formed between the two planets.

    Thoughts on whether it’s possible for such an “hourglass” planet to form?

  60. Messier Tidy Upper

    @^ Omega Baby :

    Well its certainly possible for asteroids to form or be like this – Near Earth Asteroid Toutatis & jovian trojan asteroid Hector are two examples.

    SF writer Robert L.Forward written an excellent novel (another of my faves & this time a very optimistic hard SF one) featuring an earthlike double planet with two lobes – a dry one named Roche (french for ‘Rock” and the Roche lobe concept discoverer) and an ocean one named Eau. (french for water.)

    Some folks would argue that the Earth-Moon and Pluto-Charon systems count as double planets although they’re too distant to be in the close gravitationally distorted dumbbell configuration.

    @45. Chip Says:

    …Another scenario you might explore is the possibility in such a solar system of a near miss, (which doesn’t get our planetary hero off the hook for long.) What might happen is that the two planets are flung out of their solar system or at least into wildly elliptical orbits. Moving in too close and then enormously far from the binary. After surviving all the terrible earthquakes and weird weather associated with the short near-miss event, we are treated to seasons of the coldest and longest winter imaginable (frozen atmosphere) followed by the shortest but hottest summer imaginable (molten surface).

    You may already know or remember that a lot of exoplanet’s found especially early on are in eccentric orbits with a few really extremely eccentric comet-like one’s being known. We think this is most likely due to planetary encounters with other more massive planets – essentially your scenario.

    Eg. One of the worlds orbiting Upsilon Andromedae is highly tilted out of the plane and there was one superjovian exoplanet – HD 80606b – in an a extreme comet-like orbit that the BA described in his post on it as :

    The planet’s orbit is incredibly elliptical, with a whopping eccentricity value of 0.927 — meaning the orbit is elongated like a rubber band being fought over by jealous children. It’s posited that gravitational interaction over time with a distant binary stellar companion to the star may have forced the orbit into this shape; it peaks at a distance of 125 million kilometers (75 million miles) from the star, but the planet’s 111 day orbit drops it to a mere 4 million kilometers (2.4 million miles) from the star’s surface. In the 55 days it takes to drop, it sees the disc of the star swell to 30 times its previous size, flooding the planet with nearly 800 times the amount of heat it felt at greatest distance.

    Source : BA blog article 28th Jan 2009 “Weather Sizzles on aplanet that kisses its star!” {link to follow in separate comment to avoid moderation / problems. Plus links to asteroid Toutatis etc ..]

    Actually I read somewhere that if Saturn was a bit more massive it could’ve started interacting with Jupiter in a way that would have caused us a lot of trouble – or menat we and Erath weouldn’t be here now!

    Or short answer – yes both dumbell shaped double planets and wildly eccentric comet-like orbiting “Icarus” planets exist or probably exist. :-)

  61. Messier Tidy Upper

    Forgot to note the title of Forward’s novel is ‘Rocheworld’ (published 1985) although my copy uses the alternate title of ‘The Flight of the Dragonfly’ (published 1984 ) – and there were a number of sequels to it too. :-)

    The BA’s post on the Icarus comet-like orbiting superjovian is here :

    http://blogs.discovermagazine.com/badastronomy/2009/01/28/weather-sizzles-on-a-planet-that-kisses-its-star/

    The BA’s post on Upsilon Andromedae’s weirdly orbiting world complete with excellent graphics – except that they have our own inner solar system slightly messed up (look closely near the Sun on the lower right comparison box) – is here :

    http://blogs.discovermagazine.com/badastronomy/2010/05/24/nearby-planetary-system-is-seriously-screwed-up/

    Toutatis wikipage is here :

    http://en.wikipedia.org/wiki/Toutatis-4179

    For binary asteroid Hector you’ll have to type or cut & paste from here :

    624 Hektor

    into the search box. Note that’s Hektor with a ‘k’ not ‘c’ – the more accurate Greek spelling.

    NB. I don’t want to risk posting more than 3 links as this has caused me grief here before. :-(

    Hope this is interesting / useful for y’all so late in this thread. :-)

  62. John Sandlin

    @60, OmegaBaby,

    It would be a poetic sight, but sadly for the poets, the force of gravity on the two objects would destroy the hourglass shape as it was forming. Eventually, they’d be one larger globe.

  63. nomuse

    It’s too late in the evening to break out my “Doc” Smith collection but as I recall they worked their way up…

    Boskone had been mined by the bad guys and blew up without any help from the Patrol.

    The next baddie on the list, they took out with a “free” planet. (That is, they stuck inertia-less drives on a planet, towed it to the appropriate location, then turned off the Bergenholms restoring the original inertial velocity). I think it might have been Ploor where the Patrol dropped two of them out of inertialess drive in a maneuver they called the “Nutcracker.”

    The bad guys were getting smart enough to mount massive pressor beams to ward off free planets when Kinnison formed a brain trust to invent the physics for the Nega-sphere, which was sort of a strange combination of antimatter and black hole.

    Meanwhile fun with hyperspacial tubes led to the discovery of a different dimension where the speed of light was much, much, much higher. The Patrol, never shy of taking risks with the physics of our universe, stuck engines on a planet there and got it moving really, really fast…and then dropped it back into our universe as an inertial object going several times the speed of light. Einstein may have screamed a little in his grave, but basically the result was lots of energy where a planet had been. And then THAT hit the sun of the last target on their list.

  64. Nigel Depledge

    OmegaBaby (60) said:

    For example, say the Moon was slowly getting closer to the Earth instead of moving away. If this occurred slow enough, the Earth and Moon could become tidally locked, always pointing the same face to each other.

    I think the opposite is actually true.

    The Earth-Moon system is already evolving towards being tidally locked. The Moon is already tidally locked with the Earth. As the moon saps rotational energy from the Earth via tidal interactions, it is accelerated to a higher orbit. Eventually, the Earth will be tidally locked with the moon, at which point there will be a permanent high tide in two regions (those parts of the Earth facing directly towards and away from the moon) and a permanent low tide in other regions (those areas on Earth that face perpendicularly to a line drawn between the centres of the two bodies).

  65. Owen

    Thank you for this piece. You have given me an inspiration. I have not watched this movie in a long time. I shall watch it with my mother (the woman who first inspired me to study astronomy) and my daughters, and then we shall read and discuss this blog entry. Family bonding, classic science fiction, and real science. Sounds like a great way to spend a Sunday afternoon. :)

  66. Jim Starluck

    Y’know, I always like to think that planetary impacts like this are the only sort of thing that would produce anything remotely resembling the popular perception of an asteroid belt… well, at least for a few years immediately following the impact, before all the debris has time to move apart or clump back together.

  67. Khyfka

    So, if you did happen to be on the side of the planet they was being struck – how close would the other planet get before you are killed? I would assume it wouldn’t be the actual impact that did it. How long would you have to look up and see an entire planet headed your way?

  68. Three out of every two stars is a binary.

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