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Tatooine's Double-Sunset a Common Sight

Posted by Zonk on Fri Mar 30, 2007 05:35 PM
from the double-shadows-means-twice-as-scary dept.
NASA Space Science
anthemaniac writes "Thirty years ago, Luke Skywalker beheld something that scientists are just now realizing is likely quite common in the universe: double sunsets. Astronomers have long known that binary star systems are common. And models suggested that planets could form in these systems, even though there's a double-tug of gravity on the material that would have to form a planet. Observations from NASA's Spitzer telescope, show that binary systems are just as likely to be surrounded by planet-forming debris disks are are lone stars."
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  • Quantum systems also likely to be surrounded by debris.

  • Force, not tug (Score:3, Funny)

    by 140Mandak262Jamuna (970587) on Friday March 30 2007, @05:39PM (#18550403) Journal
    It is the FORCE of gravity, not tug. Not when you are talkin' about the Pod Race Capital of the universe. At a stretch you could call the Millenium Falcon a tug, but not what gravity exerts.

    • Re: (Score:3, Funny)

      by winkydink (650484) *
      Seems to me like somebody is feeling the tug of pedantry.
    • Gravity is the result of warping space/time. As such, could it really be called a "force"? To me, "force" = applied energy.

    • Re: (Score:2)

      by Surt (22457)
      Based on all the responses to your message so far, congrats, that was quite a WHOOSH!

  • Great (Score:5, Funny)

    by eviloverlordx (99809) on Friday March 30 2007, @05:43PM (#18550445)
    More places for hives of scum and villainy!
  • Any k-paxian could have told you this.
    its common knowledge to them.

  • Planetary Orbit? (Score:3, Interesting)

    by MrSteveSD (801820) on Friday March 30 2007, @05:49PM (#18550509)
    How would the planet orbit them though?

    Would it have to be far enough away so they appeared as one, or go into some crazy chaotic close orbit?
    • Isn't that the classic 3 bodies problem?

    • Re:Planetary Orbit? (Score:5, Informative)

      by Lars T. (470328) <Lars.Traeger@go[ ... m ['ogl' in gap]> on Friday March 30 2007, @06:01PM (#18550651) Journal

      How would the planet orbit them though?

      Would it have to be far enough away so they appeared as one, or go into some crazy chaotic close orbit?
      Look at the image in TFA. Either the stars are closer than 3 AU, then the planet(s) circle around them both, or they are farther away than 50 AU, then the planet(s) circle one of them (it doesn't mention if there could be planets about both, but IMHO that's also possible). In between, no planets will form.

    • Re:Planetary Orbit? (Score:5, Insightful)

      by cswiger (63672) <chuck@codefab.com> on Friday March 30 2007, @06:09PM (#18550727) Homepage
      There are two stable possibilities: where the two stars orbit each other fairly closely (ie, 0-4 AU from the article, IIRC), and planets then orbit the common center of gravity formed by these two stars...or where one star has a very distant orbit, which is so far that it doesn't disrupt planets close in to the bigger primary.

      If the second binary star is in a medium-sized orbit (ie, somewhere between where Jupiter and Pluto are in our system), it seems to be the case that this disrupts the planet-forming disk of gas so much that no planets are likely to form.

      If you want to see a full list of all known exoplanets, go here: http://exoplanets.org/planets.shtml [exoplanets.org]
      The column marked "a (AU)" is orbital radius, where 1 AU is the earth's distance from the sun.
      • But assuming they're close together, would you really be able to see two distinct sunsets ( la Tatooine) or would it be one oddly shaped blob? I would think they'd need to be far enough apart to see the difference.

      • Re: (Score:3, Insightful)

        by Mattsson (105422)
        The bigger question would be:
        Is it possible to create an orbit around a binary system where a planet has a stable enough environment for harboring life?
         
    • if a binary system had two stars the size of our sun, then being far enough away for gravitational and seasonal stability would also mean being too far away for liquid water to exist. At least one star would have to be very large in a binary system for this to work.

      Helliconia by Brian Aldiss had a striking ternary system with a small star (with an inhabited planet) orbiting a binary system, giving a 1,500-year long mega-season that gave it regularly-occuring ice-ages.

      That seems quite viable, but it illustr

    • Re: (Score:2, Insightful)

      by Anonymous Coward
      Planets and stars technically orbit each other, strange as that may seem when you say it out loud. In the case of the earth and the sun, they both swing around a common center of gravity. Because of the huge difference in mass however, this center is still located within the body of the sun.

      Picture a long board with an anvil at one end and a small paperweight at the other. If you were to find the balance point between the two, it would certainly a lot closer to (perhaps underneath) the anvil. That st

    • Re: (Score:2)

      by Surt (22457)
      It would orbit them typically in the same sense that the earth orbits both the sun and mercury.

  • It wasn't thirty years ago... (Score:5, Funny)

    by xxxJonBoyxxx (565205) on Friday March 30 2007, @05:53PM (#18550559)

    Thirty years ago, Luke Skywalker beheld something that scientists are just now realizing is likely quite common in the universe: double sunsets.


    Luke didn't see the sunset thirty years ago - he saw it "A Long Long Time Ago (in a Galaxy Far Far Away)..."

    I can't believe I'm posting to a Star Wars item...feel like I need to take a shower now.
    • I can't believe I'm posting to a Star Wars item...feel like I need to take a shower now.

      Psst, I didn't wanna say anything man, but since you brought it up.

  • Two is Better than One (Score:5, Funny)

    by AaxelB (1034884) on Friday March 30 2007, @05:56PM (#18550597)

    Trilling and his team looked for disks in 69 binary systems between 50 and 200 light-years away from Earth. All the stars are more massive and younger than our middle-aged Sun.
    Better endowed and younger, eh? And you can have two at once? Maybe we'd better rethink our exclusive orbit with our Sun... After all, we just keep going in circles.

  • what about a double-sunset + life? (Score:5, Insightful)

    by dmoen (88623) on Friday March 30 2007, @06:01PM (#18550645) Homepage
    Planets may be common in binary systems, but what about planets that support life?

    One of the reasons that Earth can support life is that the distance between the earth and the sun remains close to a constant for the duration of Earth's orbit around the sun, so the Earth receives a fairly constant amount of solar energy. This means, for example, that the temperature doesn't go down to -200 in the winter and up to +800 in the summer.

    But in a binary system, I would imagine that orbits that provide a constant amount of solar energy in the Earth-normal range would be less likely to occur. (What would such an orbit look like when there are 2 suns?) Are there any astrophysicists out there that can comment on this?

    Doug Moen

    • Re: (Score:2, Interesting)

      by stratjakt (596332)
      "life" isn't as delicate as we've once thought, it can be supported in extreme environments, and doesnt even have to be carbon based - on this planet.

      Sure planets could support "life". What you're asking is, could they support you? Maybe not.

      Earths precarious orbit and presense of the water and the particular temperature make it suitable for our type of life - or is it the other way around, did life suit itself to the rock we happen to be stuck on?

      • Re: (Score:2)

        by fm6 (162816)

        "life" isn't as delicate as we've once thought, it can be supported in extreme environments,

        What, you mean places like volcanoes? Or ocean trenches? Those may be "extreme" compared to where you live, but by cosmic standards they're positively bucolic. Which is why there's no evidence that the other planets in our solar system are anything but sterile. You could maybe introduce life on Mars by being careless with decontaminating your space probes, but it seems unlikely that life ever evolved there.

        And Mars is pretty hospitable compared to a planet that gets blasted by a companion star one a yea

    • IANAAP either, but a planet could perhaps stay in a Lagrangian point. That would ensure the stability of the trajectory and distance.

    • Yeah I wondered about that too. But it shouldn't be too bad. F'rinstance, if both are suns like ours then the habitable zone would be wider and further out (~1.4 AU I guess). The only problem comes then from one sun occluding the other, so if the planet isn't inclined to the ecliptic too much then there will be brief, but nasty, periods when the light level drops to 50% of normal. If the suns are separated by 3 AU then half a 'cycle' (therefore one occlusion) would be about .... OK too long since I've done

    • Re: (Score:3, Interesting)

      by aldheorte (162967)
      I think it would be wrong to assume that the Sol and Earth arrangement is even the most suitable spot for our kind of life. Maybe, especially if you live in a Mediterranean environment, you think the planet is near perfect, but if you live at higher or lower latitudes or directly on the equator in desert or high humidity rainforest hothouse environments, you'll find extremes and seasonal differences brutal. Think of what an organism in even middle latitudes faces: 100 degree 100% humidity summers with ocass

      • Re: (Score:3, Interesting)

        by arminw (717974)
        .....Therefore, it's quite likely that many planets in the universe have stable periodic fluctuations.......

        The mass and distance of the sun and earth are very critical and cannot be changed very much. Making a smaller sun means the earth would need to be closer. At some point, the earth could no longer rotate independently, but its rotation would be the same as its orbit, such as Mercury. That would preclude life, since one side would be very hot and the other extremely cold. Too massive of an earth would
  • So they have debris disks. That doesn't mean that planets are likely to coalesce. I'd guess the opposite, really, that proto-planets would tend to disintegrate under such conditions.
  • That is all.

  • 500 A.U. only _relatively_ tight (Score:5, Insightful)

    by StefanJ (88986) on Friday March 30 2007, @06:34PM (#18550967) Homepage Journal
    500 A.U. is more than 10 times the orbital radius of Pluto.

    Remember the inverse square rule:

    A companion star even 40 A.U. far out would be just an especially bright star. If it had the same luminosity as the Sun, it would appear 1/1600 as bright (.0625%).

    The Tatooine scenario is still romantic fiction: Stars close enough to appear in the sky together as visible disks would probably be close enough that planets in orbit around them to have strange orbits.

    • Re: (Score:3, Interesting)

      by MichaelSmith (789609)

      500 A.U. is more than 10 times the orbital radius of Pluto.

      Brings to mind the time when I was about 12 or so and I got my hands on a 40 power telescope. With Alpha Centauri in the field changing to the higher magnification resolved the binary pair for the first time, and they are only 80 AU apart, IIRC. Doing that gives a fantastic feeling of depth. You can feel how far away it is.

      • The planet wouldnt have to much choice about it's preferred speed, if it does orbit a sun at some radius
  • ...scientists have come to the conclusion that *that's* no moon.
  • that the additional gravitational pull of a second or third sun could contribute to a more vigorous tectonic activity level than would be present in a single star system, perhaps keeping the core of the planet(s) hot and this might keep the magnetic core active enough to preserve an atmosphere.
    Maybe this would be more conducive to a life sustaining environment, even for planets further out from their sun than ours is. It's an old concept that a planet has to be just the right size, it's sun has to be just

    • perhaps keeping the core of the planet(s) hot and this might keep the magnetic core active enough to preserve an atmosphere.

      We will know more about this once we get landers on Europa and Io. Both are models for this type of planet because Juipiter is (really) the second sun we almost got.

  • One incredibly nerdish thing that always bugs me about Tatooine... how come you never see two shadows being cast on anything? Two suns == two shadows, right? I don't think that's ever been addressed in any of the re-releases.

    Whatever, none of the "improvements" have done it for me anyways. In my day, Han shot first. And we liked it that way.

    J

  • Old news (Score:4, Informative)

    by Sigma 7 (266129) on Friday March 30 2007, @07:34PM (#18551573)
    Mercury has a double sunset - with the same sun setting twice without going over the sky: http://www.time.com/time/magazine/article/0,9171,8 36746,00.html [time.com].

    This was discovered sometime in 1967.

  • doubles common (Score:3, Funny)

    by rubycodez (864176) on Friday March 30 2007, @07:42PM (#18551621)
    right, binary star systems no big deal and they could have planets. But those trinary systems, that's a whole different matter, every 22 years the habitable planets around them really, really suck. Unless you're a darkness loving carnivorous boogey-creature, then it's happy hour.
  • > Tatooine's Double-Sunset a Common Sight

    Now all the fan boys need do is tell us why it took 20 years to build the Deathstar and why Luke found Leia such a "Turn-me-on Hot Chicky Mamma ooooh yeah", and their work will be complete.

    http://www.chefelf.com/starwars/ [chefelf.com]

    • Re: (Score:3, Funny)

      by geekoid (135745)
      "...20 years to build the Deathstar ..."
      Haliburton.

      "Luke found Leia such a "Turn-me-on Hot Chicky Mamma ooooh yeah""

      Let's see:
      Teenager, in a small confined space with 2 droids, a wookie, and old man, a pirate and a princess.

      It was either the princess or the pirate.
  • The first "sci-fi" reference for two suns that I can think of comes from the Hitchhiker's Guide to the Galaxy (keep in mind, I really don't know my sci-fi at all, so I expect there are others.)

    Does anyone have an earlier reference? I suspect that Tatooine is a fairly recent reference, though popularly known it may be.

    • Tatooine also predates HHGTTG.

      I seem to remember Jules Vernes mentioning the possibility in Off on a Comet, a Journey through the Stars, but I could be misremembering. But considering that he was writing about people traveling to the moon in the 19th century, using 19th century technology, it wouldn't surprise me if he or someone else long before came up with the idea.

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