Gliese 176
| Observation data Epoch J2000.0 Equinox J2000.0 |
|
|---|---|
| Constellation | Taurus |
| Right ascension | 04h 42m 55.78s |
| Declination | +18° 57′ 29.40″ |
| Apparent magnitude (V) | 9.95 |
| Characteristics | |
| Spectral type | M2V |
| B−V color index | 1.523 ± 0.025 |
| Variable type | BY Dra |
| Astrometry | |
| Radial velocity (Rv) | 26.4105 ± 0.0004 km/s |
| Proper motion (μ) |
RA: 656.85 ± 3.81 mas/yr Dec.: -1116.20 ± 2.49 mas/yr |
| Parallax (π) | 107.83 ± 2.85mas |
| Distance | 30.2 ± 0.8 ly (9.3 ± 0.2 pc) |
| Absolute magnitude (MV) | 10.10 ± 0.06 |
| Details | |
| Mass | 0.50 ± 0.03 M☉ |
| Radius | 0.4525±0.0221 R☉ |
| Luminosity | 0.0337±0.0018 L☉ |
| Temperature | 3679±77 K |
| Metallicity [Fe/H] | –0.1 ± 0.2 dex |
| Rotation | 40.00 ± 0.11days |
| Rotational velocity (v sin i) | ≤0.8 km/s |
| Age | 0.56 Gyr |
| Other designations | |
|
HD 285968, HIP 21932, Ross 33
|
|
| Database references | |
| SIMBAD | data |
| Extrasolar Planets Encyclopaedia |
data |
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.
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.
Coordinates: 
04h 42m 55.78s, +18° 57′ 29.40″
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