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Gliese 176
Gliese 176 is a red dwarf in the constellation of Taurus. Based upon parallax measurements from the Hipparcos mission, it is located approximately 30 light-years away.〔 The star is orbited by a Super-Earth.
==Planetary system==
A planetary companion to Gliese 176 was announced in 2008.〔 Radial velocity observations with the Hobby-Eberly Telescope (HET) showed a 10.24-day periodicity, which was interpreted as being caused by a planet. With a semi-amplitude of 11.6 m/s, its minimum mass equated to 24.5 Earth masses, or approximately 1.4 Neptune masses.
Observations with the HARPS spectrograph could not confirm the 10.24-day variation.〔 Instead, two other periodicities were detected at 8.78 and 40.0 days, with amplitudes below the HET observational errors. The 40-day variation coincides with the rotational period of the star and is therefore caused by activity, but the shorter-period variation is not explained by activity and is therefore caused by a planet. Its semi-amplitude of 4.1 m/s corresponds to a minimum mass of 8.4 Earth masses, making the planet a Super-Earth.
In an independent study, observations with Keck-HIRES also failed to confirm the 10.24-day signal.〔 An 8.77-day periodicity - corresponding to the planet announced by the HARPS team - was detected to intermediate significance, though it was not deemed significant enough to claim a planetary cause with their data alone.
抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』
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