Lambda Draconis

Lambda Draconis (λ Draconis, abbreviated Lam Dra, λ Dra), also named Giausar (/ˈdʒɔːzɑːr/ JAW-zar),^[11][12] is a solitary,^[13] orange-red^[14] star in the northern circumpolar constellation of Draco. It is visible to the naked eye with an apparent visual magnitude of +3.85.^[2] Based upon an annual parallax shift of 9.79 mas as seen from the Earth,^[1] the star is located around 333 light years from the Sun.

A light curve for Lambda Draconis, potted from MASCARA data^[15][16]

λ Draconis

Location of λ Draconis (circled)
Observation data Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation	Draco
Right ascension	11h 31m 24.22075s[1]
Declination	+69° 19′ 51.8696″[1]
Apparent magnitude (V)	+3.85[2]
Characteristics
Evolutionary stage	asymptotic giant branch[3]
Spectral type	M0III-IIIa Ca1[4]
U−B color index	+1.97[2]
B−V color index	+1.62[2]
Variable type	slow irregular[5]
Astrometry
Radial velocity (Rv)	+6.58±0.30[6] km/s
Proper motion (μ)	RA: −40.97[1] mas/yr Dec.: −19.19[1] mas/yr
Parallax (π)	9.79±0.15 mas[1]
Distance	333 ± 5 ly (102 ± 2 pc)
Absolute magnitude (MV)	−1.14±0.033[7]
Details[8]
Mass	1.53±0.12 M☉
Radius	69.99+1.06 −1.10 R☉
Luminosity	884±52 L☉
Surface gravity (log g)	1.10±0.05[9] cgs
Temperature	3,761±47 K
Metallicity [Fe/H]	0.00 dex
Age	2.33±0.48 Gyr
Other designations
Giausar, λ Dra, 1 Dra, BD+70 665, FK5 433, HD 100029, HIP 56211, HR 4434, SAO 15532[10]
Database references
SIMBAD	data

This is an evolved red giant star on the asymptotic giant branch^[3] with a stellar classification of M0III-IIIa Ca1.^[4] It is a suspected slow irregular variable with a periodicity of roughly 1,100 days.^[5] It has an estimated 1.53 times the mass of the Sun and a measured radius of 70 times the radius of the Sun. It is radiating 884 times the solar luminosity from its photosphere at an effective temperature of 3,761 K.^[8]

Nomenclature

λ Draconis (Latinised to Lambda Draconis) is the star's Bayer designation.

It bore the traditional name Giausar^[17] (also written as Gianfar, Giansar and Giauzar) and Juza.^[18] This name comes from the Persian term jauzahr, referring to the nodes of the Moon's (or any) orbit.^[19] In 2016, the International Astronomical Union organized a Working Group on Star Names (WGSN)^[20] to catalogue and standardize proper names for stars. The WGSN approved the name Giausar for this star on February 1, 2017, and it is now so included in the List of IAU-approved Star Names.^[12]

In Chinese, 紫微右垣 (Zǐ Wēi Yòu Yuán), meaning Right Wall of Purple Forbidden Enclosure, refers to an asterism consisting of Lambda Draconis, Alpha Draconis, Kappa Draconis, 24 Ursae Majoris, 43 Camelopardalis, Alpha Camelopardalis and BK Camelopardalis.^[21] Consequently, the Chinese name for Lambda Draconis itself is 紫微右垣三 (Zǐ Wēi Yòu Yuán sān, English: the Third Star of Right Wall of Purple Forbidden Enclosure),^[22] representing 上輔 (Shǎngfǔ), meaning First Minister.^[23] 上輔 (Shǎngfǔ) was westernized into Sang Poo or Shaou Poo by R.H. Allen.^[18]

Namesakes

USS Giansar (AK-111) was a United States Navy Crater class cargo ship named after the star.