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Space

Several Extrasolar Planets May Be Optical Illusions 136

Posted by Roblimo from the not-everything-is-what-it-seems-to-be dept.
person-0.9a writes "Seems that a few of the extrasolar planets detected via their sun's wobble might be written off according to a CNN article. You can also read it about it in New Scientist."
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Several Extrasolar Planets May Be Optical Illusions More

Several Extrasolar Planets May Be Optical Illusions

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  • Space aliens... (Score:1, Funny)

    by Anonymous Coward
    Space aliens activating their planet-wide cloaking device?
    • Actually they are flying around the star in a huge star-spot-sized saucer, giggling to themselves, "This will f*ck up human astronomy really bad, he he he. Hey Gerz, back up few times to really mess with their puny minds. Better yet, lets all fart at the same time to give 'em a really weird spectrum to look at. They have never seen the spectrum of Theta Tau wine yet I bet, he he he."
  • Only a small number of planets are cast into doubt, those being ones around "new" stars. A very large majority of the extrasolar planets found are around very old stars.
    • Whatever the mistake, this seems to me like a "no shit" article... of course you are going to get false positives when the thing you are measuring is trillions of miles away. They still have a load of planets that weren't mistakes. And another thing to consider is that some of these stars and planets that are parsecs away don't even exist anymore...
    • the fourth rock from the sun (Mars) is REALLY there despite what the article CLEARLY states!?

      I think that you need to stop with the 'shrooms man, your theories are messed up.
    • Not only is the number relatively small, but chances are it'll be easy enough to verify whether the other planets actually exist (to my mind). The planets, after all, are (we must assume) in stable orbits; the pattern won't change. With starspots, however, they're much more likely to be transitory in nature, and therefore over time it'll become obvious which are planets; the ones that aren't will disappear or move.

      Of course, I'm assuming that starspots are like sunspots. I reckon it's a valid assumption, but what do I know?

      Oh, and while I'm here, a plug. Check out my handy-dandy extrasolar planet page [robertelliott.org], where you can calculate travel times to the various planets discovered thus far.

  • clarification of illusion (Score:4, Informative)

    by beaverfever ( 584714 ) on Thursday September 05, 2002 @07:01PM (#4203682) Homepage
    In the article it's described not as an optical illusion - it was a spectral illusion.

    I can now go to my grave knowing that at least once in my life I used the term "spectral illusion" in a serious discussion.
    • So....it's not really an optical illusion - it just looks like one.
      • The spectrum of the star is measured for signs of gravitational interference; it doesn't look like an optical illusion - it feels like one. :)

        From The New Scientist [newscientist.com] A planet with sufficient size will have a gravitational effect on the sun it orbits, causing it to move during each orbit. To a distant observer, this increases the redshift of the spectrum as the star is pulled away, and vice versa.

        • it feels like one
          No, it looks like it feels like one.

          I found this article very comforting. I've been trying for a long time now to wrap my brain around the idea of an especially big gas giant, orbiting a star down around 0.001AU, with the only observable effect being just a bit of apparent redshifting? No violent flashes as the star snarfs up the red giant until it's just a rock (or diamond? [amazon.com] )core? I suspect that all the giant, ultrashort period planets so far discovered, are false positives, attributable to this effect.
    • "I can now go to my grave knowing that at least once in my life I used the term "spectral illusion" in a serious discussion."


      This is a serious discussion?

    • I can now go to my grave knowing that at least once in my life I used the term "spectral illusion" in a serious discussion.

      And I'm sure many other Slashdot users will also be going to your grave, knowing that you got +3 Karma for that. Just don't ask how they will be paying their respect.
      • And I'm sure many other Slashdot users will also be going to your grave, knowing that you got +3 Karma for that.

        I'll freely admit that I was surprised I got modded up for that one, but maybe this one will get me back down for being off-topic. Enjoy my funeral.

  • What can we learn from this? (Score:5, Insightful)

    by wildcard023 ( 184139 ) on Thursday September 05, 2002 @07:04PM (#4203695) Homepage
    It seems that if we have discovered 100 'planets' and 95% of them really are planets, we have discovered an interesting occurance which happens to about 5% of the stars that are capable of supporting planets.

    Isn't there something we can learn from these stars? They seem to be unstable at best if they have spots that large on them. Maybe we can use this information to learn more about the formation of stable vs unstable stars.

    --
    Mike

    • Numbers Out Of Hand. (Score:5, Insightful)

      by phriedom ( 561200 ) on Thursday September 05, 2002 @07:31PM (#4203802)
      I love to see the way the story progresses. First, the Scientific American article says ONE found planet, which was suspect all along, has been disproven, and they do not expect this to apply to many other planets because it is a particularly young star.

      The CNN article turns the statement from a negative to a positive and says 95% are secure and 5% NEED TO BE CHECKED IN MORE DETAIL

      Then it gets posted on slashdot and ONE becomes SEVERAL.

      Now Wildcard has concluded that the 5% that are "unsure" do have this wild sunspot activity, and that they constitute 5% of the stars capable of supporting planets.

      Oh crap, I just fed a troll, didn't I. Shame.
    • It seems that if we have discovered 100 'planets' and 95% of them really are planets, we have discovered an interesting occurance which happens to about 5% of the stars that are capable of supporting planets.

      Actually, no. We've discovered that of the stars we thought had planets going around them, about 5% don't. We've learned nothing about which stars are capable of supporting planets.

      • "We've discovered that of the stars we thought had planets going around them, about 5% don't."

        No, they have not discovered that either. They have discovered exactly one planet that wasn't there. 5% merit further verification. There could be lots of reasons why those 5% merit further study. It may be that none of the other questionable 5% have anything to do with sunspot activity. After further study all five of them may be determined to definitely have planets.
    • These stars aren't actually unstable, they are just in the early stages of life. Kind of like puberty, going through changes until they settle down into mundain middle age.

      People are studying them though. Astronomers and Astrophycists are studying every kind of star to try and figure out how stars are formed and how they die. There is a lot that we know, but a lot more that we do not know. The planet hunters may not be interested in this star anymore, but the "star people" definately will be.

  • Guesses based on conjectures (Score:4, Interesting)

    by CommieLib ( 468883 ) on Thursday September 05, 2002 @07:06PM (#4203710) Homepage
    An astronomy prof described astronomy as that in a frosh astro course. In particular, we were discussing methods of determining stellar distance. For stars fairly close we use an ultra reliable method called paralactic displacement. For methods beyond that, we start using methods that basically say "as long as our theories about how such and such behaves turn out to be true, this method of determining stellar distance should hold true."

    This article just goes to show how fragile human knowledge is. But this is a good thing, and part of the natural progression of science.


    • > For methods beyond that, we start using methods that basically say "as long as our theories about how such and such behaves turn out to be true, this method of determining stellar distance should hold true."

      I can tell from your other comments that you're not just trashing science, but for the benefit of any jerky knees in the audience I'd like to point out that that's how everything works, whether we're pushing the limits of what science can tell us about the universe or merely trying to design a better mousetrap. At some point you've just got to go with what you think you know, and be willing to make corrections later if that's how things turn out.

      • (Am I about to start a flamewar? Please, no, I certainly won't post in one.)

        Yes, but I wish that was better recognised. There's a lot of science which definitely falls into this category - stuff like size and age of universe, planetary history and so on.

        Speaking as someone with some scientific background and an interest in religion, it's somewhat irritating when people consistently bleat about how science has proved various things like Earth being however many billion years old. No, it hasn't - and it can't, by definition, because it can't observe or repeat it - it's merely that the current theories, which seem to hold water at the moment, suggest that that's true. But the whole foundation for the theories can be a bit like a house of cards at times.

        Anyway, that's me out.
        • Whoops, forgot to add something.

          I'm not remotely intending to bash science either. Science is cool, science is how we find all sorts of things out and science, properly applied, is definitely the final word.

          But science isn't certain about a whole bunch of things people seem to think it is and I wish some people would remember this and be a little more humble in discussions.


        • > Speaking as someone with some scientific background and an interest in religion, it's somewhat irritating when people consistently bleat about how science has proved various things like Earth being however many billion years old. No, it hasn't - and it can't, by definition, because it can't observe or repeat it - it's merely that the current theories, which seem to hold water at the moment, suggest that that's true. But the whole foundation for the theories can be a bit like a house of cards at times.

          And of course the mythologies competing with science in these areas have no foundation at all.

          I fear you have completely missed my point.

          • The foundation is built on religious faith. Yes, that's rather different to science to put it mildly :-)

            Science looking at similar things is making an awful lot of deductive leaps, though, and it's quite a long way from the point of last known fact.

            I'm not suggesting the two are equal, or that religious theories should be in the textbooks. I've said before I think the kids should have them mentioned alongside in school, very much in passing, but that's another matter which I'm not about to go in to.

            Anyway, all I was doing was agreeing with your comment about science in this area being, erm, less than certain, and whingeing how it's annoying that people comment that religion is less than certain while forgetting that science is too, even if in a very different way.

            Believe me, I agree with you.
    • OK. How can we, as a platform moving through space, spot a distant object, also moving through space, and say with any accuracy that the object is X distance from us. It seems a lot like measuring the distance between rafts on a river by moving from the front of your raft to the rear of your raft and calculating the angles. It may give a ballpark, but the margin for error would be enormous. Especially when you are measuring angles comparable to the width of a dime on the moon.
      • We are quite a ways from the nearest stars. The amount the sun moves in a year compared to this distance is negligable. Therefore, we can use the position of the Earth at time zero, and zero+6 months as the base of a large triangle, and using basic trig get the distance to nearby stars. This only works for nearby stars as the angles involved get very small for farther away stars.
      • Well, the idea is that the star you are trying to measure the distance to is much closer than the 'background' stars; so the distant stars won't have a parallax shift nearly as large as the close one. Also, even through the star is moving, it won't move very far (relative to its distance) over the course of a year.

  • Reminds me of the Red Dwarf episode... (Score:3, Funny)

    by Usquebaugh ( 230216 ) on Thursday September 05, 2002 @07:08PM (#4203713)
    where Holly mistook some dust for a black hole.

    A collective whoops might be heard from some observatories.

  • Anyone who knows more care to elaborate? (Score:4, Interesting)

    by deglr6328 ( 150198 ) on Thursday September 05, 2002 @07:10PM (#4203719)
    It seems strange to me that the reason the planets were found not to exist is because the sunspots on the surface of the star somehow masqueraded as doppler shifts, thereby creating the illusion that a doppler spectroscopy observation had found a planet. This is the scenario that both news sources allude to. It seems much more likely that the giant sunspot would fool an astronomer using the so called transit photometry method of planet detection, whereby the transit of a planet in front of the stars disk dimms it slightly, having the same effect that a large sunspot would as it traverses the rotating stars viewable surface. Can anyone who knows more about this story explain what really happened?
    • So sayeth The Straits Times [asia1.com.sg]:

      >> Astronomer Gregory Henry of Tennessee State University said his analysis revealed that the
      >> ''planet'' - one of several far-flung discoveries announced with great fanfare two years
      >> ago - was actually a trick of light created by giant ''star spots'' on its sun's surface.

      So it seems CNN and New Scientist were right.

      Granted, IANAA, so I have no idea how likely that is. But remember...a hundred years ago, people probably didn't think human flight was all that likely either.

    • Re:Anyone who knows more care to elaborate? (Score:5, Informative)

      by renard ( 94190 ) on Thursday September 05, 2002 @08:15PM (#4203969)
      Sun spots can masquerade as Doppler shifts by altering the spectrum of the star systematically as the star rotates. You think it's the planet's period, but it's actually the star's rotation (at the latitude of the sunspot). That's why Greg Henry's discovery of photometric variability with the same period as the "planet" is so damning.

      Planetary transit searches will be subject to sunspots as a noise source (star's light changing by small amounts, erratically), but are unlikely to be fooled by them. A planetary transit causes the star's light to dim in a distinct flat-bottomed way that a sunspot cannot mimic.

      Note also that no one has discovered a planet yet using the transit-search technique. The transiting planet of Henry & Charbonneau was known to exist already thanks to the spectroscopic surveys.

      -Renard

    • Re:Anyone who knows more care to elaborate? (Score:5, Informative)

      by TMB ( 70166 ) on Thursday September 05, 2002 @10:18PM (#4204419)
      (preface: yes, I Am An Astronomer)

      The important thing to realize is that you're measuring the spectrum integrated over the entire surface of the star WEIGHTED BY THE FLUX (read: brightness) AT THAT PART OF THE SURFACE.

      The star is rotating, so part of the star is moving away from us and is red-shifted, while part is moving toward us and is blue-shifted. If the surface were all radiating at the same level, then we'd always see part of the spectrum blue-shifted and part red-shifted.

      Now stick a big starspot on. The starspot is fainter than the rest of the star. When the starspot is on the approaching side of the star, there is less blue-shifted light and so the net spectrum appears slightly red-shifted. Half a period later, the starspot is on the receding side of the star so there is less red-shifted light, and the net spectrum appears slightly blue-shifted.

      The end result is a spectrum that systematically shifts back and forth, very similar to that of a star with an orbiting planet.

      [TMB]

    • It was already in doubt (Score:1, Informative)

      by Anonymous Coward
      Of the two groups which (nearly simultaneously) dectected the apperent wobble 2 years ago, one wrote: [exoplanets.org]
      If photemetry or "S" value measurements continue to show periodicities similar to the observed Doppler velocity period, this would suggest that the source of variation is intrinsic to the star rather than an orbiting planet.... We are not yet completely convinced of the planet-companion interpretation for the velocity variations of HD 19622
  • The only thing that we know about them - is that they send
    us 1-photon thick ray. It's entirely possible that we are enclosed in some sphere made as a large planetarium and the stars are just small sphere holes...
    The diameter of sphere can be 1 light year or even less...

  • Optical illusions? (Score:3, Funny)

    by sulli ( 195030 ) on Thursday September 05, 2002 @07:40PM (#4203831) Journal
    Like the moon [slashdot.org]?

  • www.cnn.com (Score:1, Offtopic)

    by Elbereth ( 58257 )
    It's a good thing that this story linked to the CNN front page, because I couldn't remember what the URL is! Thanks, Slashdot.
    • It's a good thing that this story linked to the CNN front page, because I couldn't remember what the URL is! Thanks, Slashdot.
      Okay, there're many legitimate things to complain about when it comes to Slashdot:
      • Frequent double-posted stories.
      • Editorialising in the story body (from "on high") rather than in the comments.
      • Spelling, CmdrTaco.
      • All the pretentious, self-important twits, jerking off over their own inflated egos.
      • Super-moderator's occasional abuse of power.
      • The fact that we're no longer allowed to see a numerical karma count. Everyone started keeping count in their head when the new system was introduced, Taco! We're nerds: we like numbers!
      • JonKatz and michael in general.
      But complaining because the story poster linked to www.cnn.com [cnn.com] is just being a whingy bitch. (Oops, I did it too!)

      Oh well, scratch two more karma. No matter, another 34 where that came from. :)
  • Yeah the telescopes are not strong enough to see the planets, so they look at the star, if the star wobbles, they believe it has planets orbiting it.

    Would make sence if some didnt have planets....

    • Re:Of course (Score:2, Informative)

      by joh3n ( 201817 )
      Not quite. The telescopes are indeed strong enough to see the planet. In fact, you can look up in the sky and see a few of them with the naked eye. The problem is that the star is too damn bright in comparison. Also, due to atmospheric blurring effects, it is very hard to seperate the planet from the star as a light source.
    • Correct. They use 2 methods, one where they measure the star's light curve and the other the classic wobble effect as the suspected planet graviationally tugs on the star. Then they measure the time intervals between occurances to determine if it's happening at regular intervals. There are bound to be a few instances where they may misjudge. I'll bet for the most part the majority of planets found so far ARE indeed planets. I can see where LARGE sunspots on the star may fool the light curve method, some very large spots can last several rotations of the star. In any case this is really exciting stuff!
  • Quoteth the article:
    "But the researchers do not believe that many other extra-solar planets will have to be scrapped. This is because large sunspots are usually found only on young stars and most planet discoveries have orbited older ones.
    "All the other cases are pretty solid," Donahue adds. "In almost every case so far, the star has been old."    "

    Sounds like it's just the one planet that isn't really a planet, doesn't it?
    So where did the "several" in the title come from?

  • Understandable (Score:5, Funny)

    by guttentag ( 313541 ) on Thursday September 05, 2002 @08:03PM (#4203926) Journal
    I thought Earth was just an illusion when I first passed through this region of space.

    Then WHAM!!!

    Now I'm stuck here. Anyone know where I can buy secondhand trilithium crystals and a really good radar system? Apparently, mine sucked.

  • ...that Frito Lay's "Planet Lunch" is just an optical illusion as well? And here I thought I was doing something good saving my little cousins those "ploid" things...

  • The "Moon": A Ridiculous Liberal Myth (Score:5, Funny)

    by Anonymous Coward on Thursday September 05, 2002 @08:39PM (#4204057)
    It amazes me that so many allegedly "educated" people have fallen so quickly and so hard for a fraudulent fabrication of such laughable proportions. The very idea that a gigantic ball of rock happens to orbit our planet, showing itself in neat, four-week cycles -- with the same side facing us all the time -- is ludicrous. Furthermore, it is an insult to common sense and a damnable affront to intellectual honesty and integrity. That people actually believe it is evidence that the liberals have wrested the last vestiges of control of our public school system from decent, God-fearing Americans (as if any further evidence was needed! Daddy's Roommate? God Almighty!)

    Documentaries such as Enemy of the State have accurately portrayed the elaborate, byzantine network of surveillance satellites that the liberals have sent into space to spy on law-abiding Americans. Equipped with technology developed by Handgun Control, Inc., these satellites have the ability to detect firearms from hundreds of kilometers up. That's right, neighbors .. the next time you're out in the backyard exercising your Second Amendment rights, the liberals will see it! These satellites are sensitive enough to tell the difference between a Colt .45 and a .38 Special! And when they detect you with a firearm, their computers cross-reference the address to figure out your name, and then an enormous database housed at Berkeley is updated with information about you.

    Of course, this all works fine during the day, but what about at night? Even the liberals can't control the rotation of the Earth to prevent nightfall from setting in (only Joshua was able to ask for that particular favor!) That's where the "moon" comes in. Powered by nuclear reactors, the "moon" is nothing more than an enormous balloon, emitting trillions of candlepower of gun-revealing light. Piloted by key members of the liberal community, the "moon" is strategically moved across the country, pointing out those who dare to make use of their God-given rights at night!

    Yes, I know this probably sounds paranoid and preposterous, but consider this. Despite what the revisionist historians tell you, there is no mention of the "moon" anywhere in literature or historical documents -- anywhere -- before 1950. That is when it was initially launched. When President Josef Kennedy, at the State of the Union address, proclaimed "We choose to go to the moon", he may as well have said "We choose to go to the weather balloon." The subsequent faking of a "moon" landing on national TV was the first step in a long history of the erosion of our constitutional rights by leftists in this country. No longer can we hide from our government when the sun goes down.

  • Sunspots... (Score:1, Interesting)

    by Anonymous Coward

    Is "sunspots" accurate? Wouldn't it be more correct to call them "starspots" instead?

  • This solves a problem (Score:5, Insightful)

    by stwrtpj ( 518864 ) on Thursday September 05, 2002 @09:44PM (#4204269) Journal
    From the CNN article:

    Henry and his colleagues took a new look at the star identified as HD 192263, which both California and Swiss researchers said in 1999 had large, gaseous Jupiter-like planet swinging around it in a tight orbit.

    The fact that this particular planet is not a planet at all actually neatly solves a dilemma that scientists had with this discovery in the first place. If I recall correctly, the fact that this was an apparent gas-giant type planet so close to its star threw a monkey wrench into the standard theory about star system formation. The standard theory calls for only those planets sufficiently distant from the primary to retain their primordial gas envelopes. The planets closer to the star would have theirs blown off by the intense solar wind generated by the star when it first ignites. I believe the technical term for this phenominon is the T-Tauri wind.

    Naturally, the idea of gravitational capture after the star was formed is cited as an alternate explanation, but it would take a rather precise vector for the planet to be captured into such a tight orbit without crashing into the star or being flung out into space. This new information solves the problem,

    • Not quite... (Score:4, Interesting)

      by barawn ( 25691 ) on Thursday September 05, 2002 @11:12PM (#4204611) Homepage
      Unfortunately this is only one of many "hot Jupiters" as they're called. The prevalence of these odd planets is primarily due to an observation bias, as our method of detection is only sensitive to large-mass objects close to a star. Thus, when you look, and see a lot of "hot Jupiters", go fig, that's all you could detect.

      Giant planets with orbital radii 1 AU are not, however, completely impossible to understand. The current theory is that they form out beyond the ice-condensation point (this is what allows gas giants to balloon to such a huge size/mass), and then some mechanism forces them to slowly migrate inward toward the star. They've managed to do this in simulations, however, it's not a wonderfully good explanation. It doesn't, after all, explain why Jupiter is where it is for us.
  • These aren't the planets we're looking for.

    Move along.

    Move along. Move along.
  • Now I have to change my universal galactic conquest map.

    They better get it right this time, bloody amateurs.

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