Gamma Librae
Template:Location mark Location of γ Librae (circled) | |
| Observation data Epoch J2000.0 Equinox J2000.0 (ICRS) | |
|---|---|
| Constellation | Libra |
| Right ascension | Template:RA[1] |
| Declination | Template:DEC[1] |
| Apparent magnitude (V) | +3.91[2] |
| Characteristics | |
| Spectral type | G8.5 III[3] |
| Astrometry | |
| Radial velocity (Rv) | −26.71[4] km/s |
| Proper motion (μ) | RA: +65.34[1] mas/yr Dec.: +7.45[1] mas/yr |
| Parallax (π) | 19.99±0.20 mas[1] |
| Distance | Template:Rnd ± Template:Rnd ly (Template:Rnd ± Template:Rnd pc) |
| Absolute magnitude (MV) | −1.59[5] |
| Details[4] | |
| γ Lib A | |
| Mass | 1.15 Template:Solar mass |
| Radius | 11.14 Template:Solar radius |
| Luminosity | 72 Template:Solar luminosity |
| Surface gravity (log g) | 2.81±0.18[6] cgs |
| Temperature | 4826±48[6] K |
| Metallicity [Fe/H] | −0.26±0.03[6] dex |
| Rotational velocity (v sin i) | 1.60 km/s |
| Age | 4.31 Gyr |
| Metallicity [Fe/H] | {{{metal_fe2}}} dex |
| Other designations | |
| Zubenelhakrabi, Template:Odlist[7] | |
| Database references | |
| SIMBAD | data |
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Gamma Librae (γ Librae, abbreviated Gamma Lib, γ Lib) is a suspected[8] binary star system in the constellation of Libra. It is visible to the naked eye, having an apparent visual magnitude of +3.91.[2] Based upon an annual parallax shift of 19.99 mas as seen from Earth, it lies at a distance of 163 light years.
The primary component (designated Gamma Librae A) has been formally named Zubenelhakrabi Template:IPAc-en, the traditional name of the system.[9]
Nomenclature
γ Librae (Latinised to Gamma Librae) is the system's Bayer designation. The designations of the two components as Gamma Librae A and B derive from the convention used by the Washington Multiplicity Catalog (WMC) for multiple star systems, and adopted by the International Astronomical Union (IAU).[10]
Gamma Librae bore the traditional name Zuben (el) Hakrabi (also rendered as Zuben-el-Akrab and corrupted as Zuben Hakraki). The name is a modification of the Arabic زبانى العقرب Zubān al-ʿAqrab "the claws of the scorpion", a name that dates to before Libra was a distinct constellation from Scorpius.Script error: No such module "Unsubst". In 2016, the IAU organized a Working Group on Star Names (WGSN)[11] to catalog and standardize proper names for stars. The WGSN decided to attribute proper names to individual stars rather than entire multiple systems.[12] It approved the name Zubenelhakrabi for the component Gamma Librae A on 5 September 2017 and it is now so included in the List of IAU-approved Star Names.[9]
In Chinese, Script error: No such module "Lang". (Script error: No such module "Lang".), meaning Root, refers to an asterism consisting of Gamma Librae, Alpha2 Librae, Iota Librae and Beta Librae.[13] Consequently, the Chinese name for Gamma Librae itself is Script error: No such module "Lang". (Script error: No such module "Lang".), "the Third Star of Root".[14]
Properties
Because the star lies near the ecliptic it is subject to occultations by the Moon, allowing the angular size to be measured by this method.[15] As of 1940, the pair had an angular separation of 0.10 arc seconds along a position angle of 191°.[16]
The yellow-hued primary, component Aa, is an evolved G-type giant star with a stellar classification of G8.5 III[3] and an estimated age of 4.3 billion years. It has 1.15 times the mass of the Sun and has expanded to 11.14 times the Sun's radius. The star is radiating around 72 times the Sun's luminosity from its enlarged photosphere at an effective temperature of 4,786 K.[4] There is a magnitude 11.2 visual companion, component B, at an angular separation of 42.5 arc seconds along a position angle of 157°, as of 2013.[16]
At its distance, the visual magnitude is diminished by an extinction of 0.11 due to interstellar dust.[2] The system is moving closer to the Sun with a radial velocity of −26.71 km/s.[4]
Planetary system
Gamma Librae host two known planets, discovered in 2018 by doppler spectroscopy. The planets, named Gamma Librae b and Gamma Librae c, have orbital periods of Template:Convert and Template:Convert, and orbital separations of 1.24 and 2.2 astronomical units.[17]
Due to limitations of the doppler spectroscopy method, only a lower limit in the planetary masses can be measured, assuming the orbital inclination relative to Earth is a right angle. A lower inclination would imply a larger mass.[18] Nonetheless, the inclination must be larger than 70º for the planetary system to be stable. Planet b and c have minimum masses of Template:Jupiter mass respectively, and hence are gas giants. They are in a 7:3 orbital resonance, so planet c make three orbits in the same amount of time planet b make seven orbits.[17]
Template:OrbitboxPlanet begin Template:OrbitboxPlanet Template:OrbitboxPlanet Template:Orbitbox end
References
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- ↑ Template:In lang 中國星座神話, written by 陳久金. Published by 台灣書房出版有限公司, 2005, Template:ISBN.
- ↑ Template:In lang 香港太空館 - 研究資源 - 亮星中英對照表 Template:Webarchive, Hong Kong Space Museum. Accessed on line November 23, 2010.
- ↑ Cite error: Invalid
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