Gliese 176
| Observation data Epoch J2000.0 Equinox J2000.0 |
|
|---|---|
| Constellation | Taurus |
| Right ascension | 04h 42m 55.7768s[1] |
| Declination | +18° 57′ 29.417″[1] |
| Apparent magnitude (V) | +9.97 |
| Characteristics | |
| Spectral type | M2.5V[2] |
| U−B color index | +1.15[3] |
| B−V color index | +1.51[3] |
| Astrometry | |
| Radial velocity (Rv) | +29[4] km/s |
| Proper motion (μ) | RA: 659.78[1] mas/yr Dec.: –1114.66[1] mas/yr |
| Parallax (π) | 106.16 ± 2.51[1] mas |
| Distance | 30.7 ± 0.7 ly (9.4 ± 0.2 pc) |
| Absolute magnitude (MV) | 5.74 [5] |
| Details | |
| Mass | 0.49 ± 0.014[6] M☉ |
| Radius | 0.53[7] R☉ |
| Luminosity | 0.022[5] L☉ |
| Temperature | 3,520[8] K |
| Metallicity | ![\begin{smallmatrix}\left[\frac{Fe}{H}\right]\ =\ -0.1\ \pm\ 0.2\end{smallmatrix}](http://upload.wikimedia.org/wikipedia/en/math/a/2/d/a2df8cf7feb6513380c3f83e8e2a6669.png) [5] |
| Rotation | 38.92[5] days |
| Other designations | |
| Data sources: | |
| Hipparcos Catalogue, CCDM (2002), Bright Star Catalogue (5th rev. ed.) |
|
Gliese 176 (HD 285968) is a red dwarf star in the constellation of Taurus. Based upon parallax measurements from the Hipparcos mission, it is located approximately 31 light years away.[1] It has half the mass of the Sun, 53% of the Sun's radius and an apparent magnitude of +9.97.
The corona of this star has a moderate emission of X-rays at 3 × 1027 erg s–1. This indicates the star is active, and may exhibit starspots and flares much like the Sun. This is considered normal for a main sequence star of spectral class M. The proportion of elements with atomic numbers higher than helium (or metallicity) is also similar to that of the Sun.[6]
The space velocity components of this star are U = –26, V = –63 and W = –14 km/s.[10]
Contents |
[edit] Planetary system
In 2008 it was announced that this star had a planetary companion. This was based upon a five year program of radial velocity measurements at the Hobby-Eberly telescope. The estimated lower bound for the planet's mass was 24.5 times the mass of the Earth, or 0.0771 times the mass of Jupiter.[6] The orbital period of the planet is 10.24 days. Rotational modulation due to star spots was deemed unlikely as the star is thought unlikely to rotate that rapidly.[6]
A subsequent four-year study of the star showed that the original detection may have been spurious. Instead, strong evidence was detected of a planet with a lower bound of 8.4 times the mass of the Earth. The signal indicated an orbital period of 8.78 days and a semi-major axis of 0.066 AU. The thermal equilibrium temperature at that distance is 450 K. Most of the planet's mass is likely to be rock, but it may have acquired a gas atmosphere.[5]
| Companion (in order from star) |
Mass | Semimajor axis (AU) |
Orbital period (days) |
Eccentricity |
|---|---|---|---|---|
| b | >8.4 M⊕ | 0.066 | 8.78 | 0 |
| c (unconfirmed) | 0.044 M⊕ | 0.18 | 40 | 0 |
[edit] See also
[edit] References
- ^ a b c d e f Perryman, M. A. C. et al. (1997), "The Hipparcos Catalogue", Astronomy & Astrophysics 323: L49–L52, Bibcode 1997A&A...323L..49P
- ^ Endl, Michael; et al. (September 2006). "Exploring the Frequency of Close-in Jovian Planets around M Dwarfs". The Astrophysical Journal 649 (1): 436–443. arXiv:astro-ph/0606121. Bibcode 2006ApJ...649..436E. doi:10.1086/506465.
- ^ a b Upgren, A. R. (June 1974). "Five-color photometry of nearby red dwarfs. II". Publications of the Astronomical Society of the Pacific 86: 294–295. Bibcode 1974PASP...86..294U. doi:10.1086/129603.
- ^ Wilson, Ralph Elmer (1953). General catalogue of stellar radial velocities. Carnegie Institution of Washington. http://adsabs.harvard.edu/abs/1953QB901.W495...... Retrieved 2007-05-14.
- ^ a b c d e Forveille, T.; et al. (January 2009). "The HARPS search for southern extra-solar planets. XIV. Gl 176b, a super-Earth rather than a Neptune, and at a different period". Astronomy and Astrophysics 493 (2): 645–650. Bibcode 2009A&A...493..645F. doi:10.1051/0004-6361:200810557.
- ^ a b c d Endl, Michael; Cochran, William D.; Wittenmyer, Robert A.; Boss, Alan P. (February 2008). "An msini = 24 M⊕ Planetary Companion to the Nearby M Dwarf GJ 176". The Astrophysical Journal 673 (2): 1165–1168. Bibcode 2008ApJ...673.1165E. doi:10.1086/524703. http://www.iop.org/EJ/article/0004-637X/673/2/1165/73007.html.
- ^ Johnson, H. M.; Wright, C. D. (November 1983). "Predicted infrared brightness of stars within 25 parsecs of the sun". Astrophysical Journal Supplement Series 53: 643–711. Bibcode 1983ApJS...53..643J. doi:10.1086/190905.
- ^ Morales, J. C.; Ribas, I.; Jordi, C. (November 2007). "Distances and atmospheric parameters of MSU stars". VizieR On-line Data Catalog: J/A+A/478/507. Originally published in: 2008A&A...478..507M 347: 80507. Bibcode 2007yCat..34780507M.
- ^ "LHS 196 -- High proper-motion Star". SIMBAD. Centre de Données astronomiques de Strasbourg. http://simbad.u-strasbg.fr/simbad/sim-basic?Ident=LHS+196. Retrieved 2009-11-13.
- ^ Gliese, W. (1969). "Catalogue of Nearby Stars". Veröffentlichungen des Astronomischen Rechen-Instituts Heidelberg 22: 1. Bibcode 1969VeARI..22....1G.
[edit] External links
- "Notes for star HD 285968". The Extrasolar Planets Encyclopaedia. http://exoplanet.eu/star.php?st=HD+285968.
Coordinates: 
04h 42m 55.7768s, +18° 57′ 29.417″
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