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| dist_ly = 20.37 | dist_pc = 6.26 | class = M3V〔 〕 | mass = 0.31〔 〕 | radius = 0.29〔 | temperature = 3480 ± 48〔 〕 | metallicity = −0.33 ± 0.12〔 | age = 7 – 11〔〔Selsis 3.4-page 1382 "lower limit of the age that, considering the associated uncertainties, could be around 7 Gyr", "preliminary estimate", "should not be above 10-11 Gyr"〕 }} Gliese 581 g , (also known as Gl 581 g or GJ 581 g) sometimes unofficially named Zarmina, is an unconfirmed (and disputed) exoplanet claimed to orbit the red dwarf Gliese 581, about 20 light-years from Earth in the constellation of Libra. It is the sixth planet purportedly discovered orbiting the star. The discovery was announced by the Lick-Carnegie Exoplanet Survey in late September 2010, after a decade of observation. However, the ESO/HARPS survey team was not able to confirm that the planet exists. Gliese 581 g has attracted attention because it is near the middle of the habitable zone of its parent star. That means it could sustain liquid water on its surface and could potentially host life similar to that on Earth (the planet is expected to have temperatures around −37 to −11 °C). If it is a rocky planet, favorable atmospheric conditions could permit the presence of liquid water, a necessity for all known life, on its surface. With a mass of 2.2 times Earth's, Gliese 581 g is considered Earth sized and is the planet closest in mass to Earth known in a habitable zone. This makes it one of the most Earth-like Goldilocks planets found outside the Solar System and one of the exoplanets with the greatest recognized potential for harboring life. Gliese 581 g is also notable for having the highest ESI until Gliese 667 Cc discovered a year later. The supposed detection of Gliese 581 g after such a short period of searching and at such close proximity has led some astronomers to hypothesize that the proportion of stars with habitable planets may be greater than ten percent. ==Discovery== The planet was claimed to be detected by astronomers in the Lick-Carnegie Exoplanet Survey, led by principal investigator Steven S. Vogt, professor of astronomy and astrophysics at the University of California, Santa Cruz and co-investigator R. Paul Butler of the Carnegie Institution of Washington. The discovery was made using radial velocity measurements, combining 122 observations obtained over 11 years from the High Resolution Echelle Spectrometer (HIRES) instrument of the Keck 1 telescope with 119 measurements obtained over 4.3 years from the High Accuracy Radial Velocity Planet Searcher (HARPS) instrument of the European Southern Observatory's 3.6 m telescope at La Silla Observatory.〔 After subtracting the signals of the previously known Gliese 581 planets, ''b'', ''c'', ''d'' and ''e'', the signals of two additional planets were apparent: a 445-day signal from a newly recognized outermost planet designated ''f'', and the 37-day signal from Gliese 581 g.〔 The probability that the detection of the latter was spurious was estimated at only 2.7 in a million.〔 The authors stated that while the 37-day signal is "clearly visible in the HIRES data set alone", "the HARPS data set alone is not able to reliably sense this planet" and concluded, "It is really necessary to combine both data sets to sense all these planets reliably."〔 The Lick–Carnegie team explained the results of their research in a paper published in the ''Astrophysical Journal''. Although not sanctioned by the IAU's naming conventions, Vogt's team informally refers to the planet as "Zarmina's World" after his wife, and some cases simply as Zarmina. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Gliese 581 g」の詳細全文を読む スポンサード リンク
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