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European astronomers unable to confirm rival team’s potentially habitable planet

The views expressed are those of the author and are not necessarily those of Scientific American.


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Gliese 581 planetary systemTwo of the world’s most accomplished teams of exoplanet hunters are at odds over one group’s claimed detection of a world billed as the most habitable planet yet discovered outside the solar system.

In question is the existence of Gliese 581g, which a group of American researchers announced in a September 29 teleconference that they had detected orbiting a small, dim star 20 light-years away. The planetary system around the star Gliese 581 was already known to harbor four planets; Steven Vogt of the University of California, Santa Cruz, and Paul Butler of the Carnegie Institution of Washington announced that they had inferred the presence of two more by the wobble of the host star as the gravitational pull of orbiting planets tugged it about.

The U.S. group used 122 of their own measurements of the star Gliese 581, taken at the 10-meter Keck I telescope in Hawaii, as well as 119 publicly released measurements obtained by a competing group using the European Southern Observatory’s 3.6-meter telescope at La Silla Observatory in Chile. Together the data implied the presence of six planets in total, with the new worlds assigned by convention the names Gliese 581f and Gliese 581g. The latter planet made quite a splash; at just a few times the mass of Earth and with an orbit inside the star’s temperate, so-called Goldilocks zone, liquid water and—just possibly life—could potentially exist there.

But at an International Astronomical Union symposium on planetary systems being held this week in Turin, Italy, a member of the European team said that the Goldilocks planet did not appear in a larger, updated data set from La Silla. According to Science, the European data now include 180 observations of Gliese 581. "We do not see any evidence for a fifth planet," Francesco Pepe of the Geneva Observatory said in an e-mail to Science, adding that the precision of the measurements was insufficient to rule out its presence. In e-mail correspondence with Astrobiology Magazine, Pepe noted that his group could not confirm the presence of the other newfound planet, Gliese 581f, either.

Both Butler and Vogt have told reporters that they cannot comment on their competitors’ results, because the new data have not been published. But the impending stand-off pits two of the field’s most renowned research groups against one another. Pepe’s collaborators Michel Mayor and Didier Queloz in 1995 became the first astronomers to find an exoplanet orbiting a sunlike star, a discovery that triggered an avalanche of research that has in the intervening years produced nearly 500 new planetary discoveries.

Butler, Vogt and their colleagues are no slouches, either, having contributed heavily to that total. "In 15 years of exoplanet hunting, with over hundreds of planets detected by our team, we have yet to publish a single false claim, retraction or erratum," Vogt wrote in an e-mail to SPACE.com. He told the Web site that he stands by the data and analysis that led to the proposed existence of Gliese 581g: "I feel confident that we have accurately and honestly reported our uncertainties and done a thorough and responsible job extracting what information this data set has to offer."

Schematic showing the proportions of the Gliese 581 system in relation to the solar system: Zina Deretsky/NSF





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  1. 1. silvrhairdevil 4:35 pm 10/14/2010

    If there is liquid water, there will inevitably be life.

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  2. 2. rocket7777 9:34 am 10/15/2010

    I would say within 20-50 years we will have a computer with IQ of 100 and few years after that, hundred times smarter.

    It will be waste of time sending human to outer space.

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  3. 3. silvrhairdevil 12:49 pm 10/15/2010

    The whole point of exploring space and exo-planets is to get humans off Earth and colonize.

    Get all our eggs out of the one basket, so to speak.

    Gonna need people for that – robots won’t be able to do it alone.

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  4. 4. ennui 9:04 pm 10/15/2010

    The Heavy Lifter will be sent out and tll us in about thousand years if that was correct.
    The Flying Saucer People would fly there in a few months time as they do not believe that antique technology is the only way to get anywhere, unlike American Taxpayers.

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  5. 5. aeebee50 11:02 pm 10/15/2010

    I think Gliese 581g,Goldilocks, is a wondeful discovery and hope for enlarging populated planet. If nothing else, it could be a way station for our space travelers. I wish I could be the first to put a Christian flag on it.

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  6. 6. bewertow 3:53 am 10/16/2010

    How can you have a Christian flag? It’s a religion, not a country.

    Also, there’s no need to pollute even more of the universe with archaic superstitions.

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  7. 7. focalist 5:57 am 10/16/2010

    You do understand that the "observation" of the planet is simply inferring that it exists by analyzing tiny fluctuations in the host star’s spin, right? Let’s not get too far ahead of ourselves.

    Additionally (and I’m betting I’m right on this), we are going to find that there may be other factors in play or calculation errors that will be refined out. In short, at BEST, we’re making an educated guess that there’s something there. We don’t yet have the ability to actually CONFIRM.

    I think many people are under the impression someone’s "seen" a rock zipping through space, not determined there’s one there by indirect observation.

    The ability to "see" in one spectrum or another at these distances may come, but for now, we have to rely on indirect observation.. which is prone to error. To observe indirectly, you need to know ALL the factors, and we may know less of them than we think…

    Just my opinion..

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  8. 8. jtdwyer 8:03 am 10/16/2010

    IMO, there’s no purpose in our infesting any other planet if we’re incapable of managing the Earth, the planet that provided all that we could want or need, that we were born to live on. We certainly won’t find any place better suited to our continued existence. Stop dreaming and live!

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  9. 9. silvrhairdevil 9:01 pm 10/16/2010

    Just as there was no point in infesting North America when Europe was providing all needs.

    Humanity will eventually "infest" the whole cosmos unless we are physically stopped.

    To think otherwise is unrealistic.

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  10. 10. aeebee50 12:23 am 10/17/2010

    I think this site said scientific American, and as an American I can use my free speech and I am an American that pays taxes. When at Nasa, people were going to lose their jobs, the ones with Obama stickers were laid off first. I do not have an Obama sticker, but I vote. You can have your opinion, I can have my opinion(I am self-employed and retired). I support space program and Science.

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  11. 11. jtdwyer 6:07 pm 10/17/2010

    I think its more accurately said that western society had already deforested the areas near the overpopulated major cities and obliterated the fresh water fishes from the rivers of Europe by the time the discovered America. That had all occurred during the population boom following the Little Ice Age.

    Western society already had its opportunity with the New World’s enormous resources and blew it.

    However, I’d bet that no human colony will ever persist outside the perfect environment of Earth: in effect we are physically stopped. To think otherwise is unrealistic.

    To fantasize of another New World that would certainly be less hospitable than even the polluted, overpopulated Earth is ludicrous. Even if it were possible for a few of us to go there survive and prosper, billions of humans would be left here on Earth to suffer and die.

    Our only real mission is to survive and prosper here on Earth, if we can possibly continue to do so.

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  12. 12. jtdwyer 6:09 pm 10/17/2010

    Of course, it goes without saying that this is only my opinion: all others are free to spend their lives fantasizing of a better life somewhere else…

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  13. 13. LarryB 8:01 pm 10/18/2010

    Even if Goldilocks did exist, and we could feasibly make it there to colonize, who decides who can go?

    Those who have money, "perfect" genetics and above average IQ’s?

    Link to this
  14. 14. biosensei 4:30 pm 10/21/2010

    As I recall the tale of Goldilocks, when she got to the nice warm house in the woods, where the porridge was ‘just right’, she also encountered the Bears, who were unhappy at her arrival. Among the lessons we should pick up from this story are that, if we should ever get there in anything like human form, we should be polite and knock first, then refrain from eating all the porridge and breaking the chairs. Anyway, I bet the equivalent of Bears [or Aliens] will be virulent bacteria and viruses… not so good for Hollywood box-office takings but more likely to be a big problem than spiky things with teeth, exotic weapons or acid blood.
    Just a thought. Maybe it could even end with "and the people realised that they had all they really needed right under their feet, and they all lived happily ever after"…

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