Earth-like planets Gliese 581 g and d likely dont exist, study saysNew method to account for star signals another blow to controversial planetsEmily ChungCBC NewsPosted:Jul 04, 2014 4:58 PM ETLast Updated:Jul 04, 2014 5:01 PM ETWhen the discovery of Gliese 581 g was announced in 2010, there was alot of excitement because it was in the habitable zone of its red dwarf star – the Goldilocks region – not too hot and not too cold – where liquid water, and therefore life, could potentially exist.European Southern ObservatoryAnother study has cast doubt on the existence of two of the first Earth-sized planets discovered outside our solar system that could potentially host liquid water, and therefore life. But it may also have uncovered a way to make detecting new planets easier.When thediscovery of Gliese 581 g was announced in 2010, there was a lot of excitement because it was in the habitable zone of its red dwarf star – the Goldilocks region– not too hot and not too cold – where liquid water, and therefore life, could potentially exist. The planet appeared to be just 1.2 to 1.4times larger than Earth, and therefore likely to have a rocky surface.Their signals are so small thatjust a very small tweak in how you analyze the data can make the difference to whether you see one planet orthe other- Paul Robertson, Penn State UniversityAnother planet in the system, Gliese581 d, announced in 2007, was on the edge of the habitable zone.They were very high value targets if they were real, said Paul Robertson, a postdoctoral researcher at Penn state University and the lead author of the new study, published this week in Science.But unfortunately we found out that they werent.The two planets have actually been controversial since they were discovered using a method that looks for small changes in the colour of a stars light caused by thetug of a planets gravity.Robertson says its because, if theseparticular planets exist, they have very low masses.And their signals are so small that just a very small tweak in how you analyze the data can make the difference to whether you see one planet or the other.Several studies have disputed the planets existence, based on different methods of analyzing the signals and ways of trying to sharpen them up. Among them wasone by Phil Gregory, professor emeritus at the University of British Columbia. Another, by a Swiss teamusing additional data, prompted thescientists who discovered Gliese 581 g, Steve Vogt of the University of California Santa Cruz and Paul Butler of the Carnegie Institution for Science in Washington, D.C., to publish a new paper in 2012 criticizing the Swiss teams analysis and reaffirming the existence of Gliese 581g with their own analysis.Robertson said that in his case, he and his colleagues were not trying to disprove the existence of Gliese 581 g, but to find a way to sharpen up small signals from planets and make them more visible by correcting for the activity of the star, which can also cause small shifts in the colour of a stars light.Blue versus redVogt and Butler had previously done corrections using a standard method that looks at two colours emitted by calcium in a star, which are on the blue/violet end of the colour spectrum.Robertson instead used a red colour emitted by hydrogen and analyzed the same data used in Vogt and Butlers 2012 paper.Robertson said that works better in this case because Gliese 581 is a very cool star, and it doesnt put outa lot of blue light.When applied to Gliese 581, the new correction made signals from three of the planets – b, c, and e - around the star appear sharper. The researchers say this confirms that Gliese has exactly three planets.Robertson said that the technique should work in general for cooler, low mass stars and boost the signals of small planets.I hope this research points the wayforward toward finding exciting new planets hidden beneath stellar signals, he added.Vogt and Butler declined requests from CBC to comment on the new research.University of British Columbia researcher Phil Gregory wrote in anemail to CBC News that the new study improves understanding of the Gliese 581 system and will cause astronomers to pay more attention to all indicators of a stars activity, even if it sadly removes a potentially interesting planet near the habitable zone.
Posted on: Wed, 29 Oct 2014 07:31:54 +0000
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